Grade 10 Unit AP.3 - Properties of Matter



PhysicsGrade 10 Advanced Level Properties of MatterPhysics42781313704206184515557539790433904619558030670537960302063751228725188595-251455662496-504825-666750ContentsUNIT 3: Properties of matter-476250154305-890270353695Core Standards…………………………….…….. 3 Objectives…………………………………....…….. 427.1-27.2 Kinetic particles model…………….........………….... 5 27.3 Thermal expansion….……..............................….. 1827.5 Freezing water……...........................................….. 2327.6 Density ……….……..........................................….. 2627.7 Pressure………………….................................….. 3427.8 Hydraulic system……….…….........................….. 4127.9 Buoyancy............................................................….. 46-30480046990 Questions………………………………............….. 55-68326071755References………………………..…………...…..... 614659289-211540-151547-21154010A.27.1 Describe the kinetic particle model for solids, liquids and gases, and relate the difference in the structures and densities of solids, liquids and gases to the spacing, ordering and motion of particles.10A.27.2 Use the kinetic particle model to explain fluid pressure, freezing, melting, boiling, evaporation, crystallisation and the Brownian motion.10A.27.3 Use the kinetic particle model to explain thermal expansion of solids and liquids. List some of the problems this phenomenon can cause and how we solve them, and also list ways in which we make use of this phenomenon.10A.27.5 Explain how the anomalous expansion of water results in ice forming on the surface of water and not at the bottom, and understand the importance of this to the survival of living things.10A.27.6 Know and use the concept of density.10A.27.7 Understand and use the term pressure in the contexts of pressure exerted by a solid object and fluid pressure, and derive and use the relationship p?=?gh..10A.27.8 Explain, in terms of the particle model, the hydraulic transmission of a force and know and explain quantitatively some common applications..10A.27.9 Understand why some objects float on water but others do not, and relate upthrust on a floating body to the weight of the fluid displaced.-215265-4572004526915-457200By the end of the unit, students explain observations such as expansion, freezing, melting, boiling, evaporation, crystallisation, the Brownian motion and fluid pressure in terms of particle interactions. They have knowledge of the anomalous expansion of water and its importance. They understand density, flotation and pressure in solids and fluids, which they apply to hydraulics and pneumatics.Students who progress further use the concept of expansivity to solve numerical problems. They derive and use the expression p = gh, and relate the upthrust on a floating body to the weight of fluid displaced. Kinetic particles model????? ?????? ????????27.1-27.2Matter is anything that has mass and occupies space.?????? ?? ?? ?? ?? ???? ????? ??? ?? ??????All matter is made up of tiny particles (atoms, molecules or ions)?? ?????? ????? ?? ?????? ????? (?? ???? ???? ?? ?????? ?? ??????)Matters can exist in 3 states: solid, liquid and gas.???? ?????? ?? ????? ???? ??: ?????? ?????? ???????? ????????These three forms of matter are called states of matter.????? ??? ??????? ?????? ?????? ??????As shown here, water (liquid) can exist as ice (solid), or water vapor (gas).4000500699135-101606985002163445599440??? ?? ???? ?? ????? ?????? ????? (????) ????? ???? ?? ???? ??? ??? ??? (???) ?? ?? ??? ???? (???).Think-133350-485775Why do you smell food from a distance away? What about perfumes? How are the bees attracted to the flowers?????? ?????? ?? ??? ????? ?????? ?? ????? ?????? ????? ?? ??????? ?????? ????? ????? ??? ????????Kinetic theory of matter ????? ?????? ???????? ??????The kinetic particle theory is a model used to explain the properties of matter. ?????? ????? ?????? ???????? ?????? ???? ??????.Kinetic theory of matter states that: ??? ????? ?????? ???????? ???: All matter is made up of tiny particles (the particles are attracted to each other by attractive force)????? ?? ?????? ?? ?????? ???? ?? ????? (?????? ???????? ???? ????? ???? ???) The particle model of a Gas??????? ??????? ??????? A gas has no fixed shape or volume, but always spreads out to fill any container.??? ??????? ??? ?? ??? ???? ?????? ????? ????? ?????? ?????? ???. 393382552705There are almost no forces of attraction between the particles so they are completely free of each other. ?? ???? ??????? ??? ????? ??? ???????? ???? ??? ??? ?????? ????? ?? ?????.The particles are widely spaced and scattered at random throughout the container so there is no order in the system.???? ?????? ????? ??? ???????? ?????? ???????? ?? ?????? ?????? ??? ???? ??? ??? ??? ???? ????.The particles move rapidly in all directions, frequently colliding with each other and the side of the container.????? ???????? ????? ?? ???? ????????? ??????? ???????? ?????? ??????? ?????? ??????.With increase in temperature, the particles move faster as they gain kinetic energy.?????? ???? ??????? ???? ???? ???????? ???????? ????? ???? ???? ??????.Using the particle model to explain the properties of a Gas????? ???? ??????? ?? ??? ??????? ???????Gases have a very low density (‘light’) because the particles are so spaced out in the container (density = mass / volume).????? ??????? ???? ?? ????? (?????) ??? ???????? ?????? ?????? ????? ????? ????(??????? = ?????? / ?????) Density order: solid > liquid >>> gases ????? ???????: ????? > ?????? >>> ?????Gases flow freely because there are no effective forces of attraction between the gaseous particles - molecules. ????? ??????? ????? ???? ??? ??? ??????? ??? ???????? (????????).Ease of flow order: gases > liquids >>> solids (no real flow in solid unless you powder it!) ????? ???? ???? ??????: ??????? > ??????? >>> ?????? ?????? ((????? ?? ???? ?????? ??????? ?????? ?????? ?? ?? ??? ?? ???? ?????) Because of this gases and liquids are described as fluids. ???? ????? ??????? ???? ??????? ???????? ????????.3467100102870Gases have no surface, and no fixed shape or volume, and because of lack of particle attraction, they always spread out and fill any container (so gas volume = container volume).??? ??????? ??? ???? ??? ??? ?? ??? ???? ???? ????? ?????? ?? ??? ??????? ??? ????????. (??? ????? ?? ??? ?????? ?????? ??)The particle model of a Liquid??????? ??????? ???????4619625246380A liquid has a fixed volume at a given temperature but its shape is that of the container which holds the liquid.??????? ??? ???? ?? ???? ????? ?????? ???? ??? ?? ??? ???? ??? ???? ??? ?????? ??????. There are much greater forces of attraction between the particles in a liquid compared to gases, but not quite as much as in solids. ??? ??????? ??? ???????? ???? ???? ?? ??????? ???? ??? ????? ?????? ??????.Particles quite close together but still arranged at random throughout the container, there is a little close range order as you can get clumps of particles clinging together temporarily. ???????? ??????? ?? ????? ???????? ????? ??? ??? ??? ??????? ?????? ?? ???? ????? ???????? ???? ?????? ??????.5038725173990Particles moving rapidly in all directions but more frequently collisions with each other than in gases due to shorter distances between particles. ????? ???????? ?? ???? ????????? ???? ????? ????????? ??????? ???? ???? ?? ???? ??????? ????? ??? ?????? ???????? ???????.With increase in temperature, the particles move faster as they gain kinetic energy, so increased collision rates, increased collision energy and increased rate of diffusion.?????? ???? ??????? ????? ???? ???????? ?????? ???? ???? ???? ???????? ????? ???? ??????? ?????? ???? ?????? ??? ????????.Using the particle model to explain the properties of a Liquid????? ???? ??????? ?? ??? ??????? ???????Liquids have a much greater density than gases (‘heavier’) because the particles are much closer together because of the attractive forces. ??????? ????? ???? ?? ??????? (????) ???? ????? ???????? ?????? ??? ??????? ?????.Liquids usually flow freely despite the forces of attraction between the particles but liquids are not as ‘fluid’ as gases. ????? ??????? ????? ???? ??? ????? ?? ??? ??????? ??? ???????? ???? ?????? ?? ????? ???? ???? ???????.Note 'sticky' or viscous liquids have much stronger attractive forces between the molecules BUT not strong enough to form a solid. ???? ?? ??????? ?????? ????? ???? ??????? ??? ???????? ???? ?? ????? ??? ????? ?????? ???? ????.Liquids have a surface, and a fixed volume (at a particular temperature) because of the increased particle attraction, but the shape is not fixed and is merely that of the container itself. ??????? ??? ???? ?????? ????? ??? ???? (??? ????? ????? ?????) ???? ??? ??????? ??? ????????? ??? ??????? ????? ????? ?????? ????? ???? ??? ?????? ?????? ???.Liquids seem to have a very weak 'skin' surface effect which is caused by the bulk molecules attracting the surface molecules disproportionately.??????? ??? ???? ???? ???? ??? ????? ?????? ?????. Liquids are not readily compressed because of the lack of ‘empty’ space between the particles. ??????? ?? ???? ???????? ?????? ???? ??? ???????? ??????? ??? ????????.Liquids will expand on heating but nothing like as much as gases because of the greater particle attraction restricting the expansion (will contract on cooling). ????? ??????? ???????? ???? ??? ???? ???? ???? ??????? ???? ????? ??? ??????? ??? ?????? ??????? ????? ????? ????? ??????.Note: When heated, the liquid particles gain kinetic energy and hit the sides of the container more frequently, and more significantly, they hit with a greater force, so in a sealed container the pressure produced can be considerable! ???? ??? ?? ???? ????? ??????? ??? ???????? ????? ???? ????? ???? ????? ???? ???????? ?????? ??????? ?????? ??? ???? ????? ?????? ??? ???????.The natural rapid and random movement of the particles means that liquids ‘spread’ or diffuse. Diffusion is much slower in liquids compared to gases because there is less space for the particles to move in and more ‘blocking’ collisions happen.?????? ????????? ???????? ???? ?? ?????? ?????? ???? ?????? ??????? ??? ???? ?? ?????? ??????? ???? ??? ???????? ???? ????? ???? ???????? ?? ???? ???????. Evidence for random particle movement in liquids: ?????? ??? ?????? ????????? ???????? ?? ???????:4315460460375If colored crystals of e.g. the highly colored salt crystals of potassium manganate (VII) are dropped into a beaker of water and covered at room temperature. Despite the lack of mixing, convection etc. the bright purple color of the dissolving salt slowly spreads throughout all of the liquid but it is much slower than the gases. ??? ??? ??????? ????? ????? ?? (?? ??? ????? ???? ????) ????? ????? ???????? ?????????? ?? ???? ????? ?? ??? ?? ????? ???? ????? ?? ????? ????? ??? ???????? ??? ????? ?? ??? ?????? ??? ????? ?? ????? (?????? ??????).The same thing happens with dropping copper sulphate crystals or coffee granules into water and just leaving the mixture to stand.??? ???????? ??????? ??? ??????? ??????? ?? ??????? ?????? ?? ?????? ?? ??????. 4251960224155 When pollen grains are viewed under a microscope they appear to 'dance around' when illuminated with a light beam at 90o to the viewing direction. This is because the pollen grains show up by reflected light and 'dance' due to the millions of random hits from the fast moving water molecules. This is called 'Brownian motion' after a botanist called Brown first described the effect. At any given instant of time, the hits will not be even all round the pollen grain, so they get a greater number of hits in a random direction.??? ?????? ???? ?????? ???????? ?? ??? ?? ???? ??????????? ??? ???? ????? ???????? ???? ????? ??????? ????????? ???? ??????? ?? ?????? ????? ???? ???? ??????? ????????? ??? ????? ????? ?????? ?????? ??? ?? ??? ???????.The particle model of a Solid??????? ??????? ??????A solid has a fixed volume and shape at a particular temperature unless physically subjected to some force. ????? ??????? ?????? ??? ??? ??? ???? ?????? ?? ????? ??????? ??????? ??? ?? ???? ????? ??? ??????.The greatest forces of attraction are between the particles in a solid and they pack together as tightly as possible in a neat and ordered arrangement. ??? ??????? ??? ?????? ?????? ?????? ????? ????? ????? ????? ???????? ?????? ?? ????? ????.The particles are too strongly held together to allow movement from place to place but the particles vibrate about their position in the structure.???????? ??????? ???? ???? ??? ?? ????? ?? ???? ???? ????? ???? ?? ??????.With increase in temperature, the particles vibrate faster and more strongly as they gain kinetic energy.?????? ???? ??????? ??? ???? ?????? ???????? ???? ????? ????? ????.Using the particle model to explain the properties of a Solid????? ???? ?????? ?? ??? ??????? ???????Solids have the greatest density (‘heaviest’) because the particles are closest together. ????? ?????? ?????? ????? (??? ??????) ???? ????? ???????? ????? ?????.Solids cannot flow freely like gases or liquids because the particles are strongly held in fixed positions.?? ????? ?????? ?????? ????? ??? ?? ??????? ???????? ???? ??? ??? ??????? ??? ????????. Solids have a fixed surface and volume (at a particular temperature) because of the strong particle attraction. ?????? ?????? ??? ???? ???? ??? ?? ??? ??? ???? ??? ???? ??????? ??????? ???? ??? ??????? ??? ????????.Solids are extremely difficult to compress because there is no real ‘empty’ space between the particles. ?? ????? ???? ??? ?????? ?????? ???? ?????? ???????? ??? ????????.Solids will expand a little on heating but nothing like as much as liquids because of the greater particle attraction restricting the expansion and contraction occurs on cooling. ????? ?????? ?????? ?????? ??? ?????? ??????? ???? ??? ????? ?????? ??????? ?? ??????? ???? ???? ??? ??????? ??? ???????? ????? ????? ????? ??????.The expansion is caused by the increased energy of particle vibration, forcing them further apart causing an increase in volume and corresponding decrease in density. ????? ?????? ???? ????? ???? ?????? ???????? ???? ?????? ??????? ???????? ????? ?????? ???? ??????? ???? ?????? ???? ?????? ??? ????? ????? ?????? ???? ??? ???????.Diffusion is almost impossible in solids because the particles are too closely packed and strongly held together with no ‘empty space’ for particles to move through.??????? ????? ???? ?????? ?????? ??? ???????? ???? ????? ???????? ???????? ???? ???? ??? ????? ??? ???? ?????? ????? ???? ????? ??? ????????.Evaporation and Boiling (liquid to gas)?????? ???????? (?????? ?? ?????? ??????? ?????? ???????)On heating particles gain kinetic energy and move faster. ????? ???????? ???? ????? ?? ???? ??????? ??? ?? ????? ????.In evaporation and boiling the highest kinetic energy molecules can ‘escape’ from the attractive forces of the other liquid particles. ??? ??????? ?????? ???????? ??? ?????? ??????? ?????? ?????? ?? ??? ??????? ??????? ??? ???? ????????.472630598425The particles lose any order and become completely free to form a gas or vapor. ???? ???????? ??????? ???? ???? ???? ????? ??? ?????? ???? ???? ????? ?????? (???)Energy is needed to overcome the attractive forces in the liquid and is taken in from the surroundings. ?????? ??? ??? ??????? ??? ???????? ?? ?????? ?????? ???? ?? ????? ??????.If the temperature is high enough boiling takes place. ??? ???? ??????? ?????? ????? ????? ??? ???? ???? ???????. Evaporation takes place more slowly than boiling at any temperature between the melting point and boiling point, and only from the surface, and results in the liquid becoming cooler due to loss of higher kinetic energy particles. ???? ????? ????? ???? ?? ????? ??????? ??? ?? ???? ?? ??? ???? ?????? ????? ???????. ????? ????? ?????? ??? ?? ??? ?????? ????? ???? ?????? ???? ????? ?????? ???? ???? ???????? ??? ??????? ??????.Melting (solid to liquid) ???????? (?????? ?? ?????? ?????? ?????? ???????)When a solid is heated the particles vibrate more strongly as they gain kinetic energy and the particle attractive forces are weakened. ??? ????? ?????? ?????? ???? ???????? ????? ???? ????? ???????? ????? ???? ???? ??? ???? ??????? ??? ??? ??????? ?????.Eventually, at the melting point, the attractive forces are too weak to hold the particles in the structure together in an ordered way and so the solid melts. ?????? ??? ?????? ?????? ????? ???????? ???? ??? ??????? ?? ???? ??????? ??? ?????? ?????? ??? ???????? ?? ??????? ?????? ?????? ????? ??????.The particles become free to move around and lose their ordered arrangement. ???? ???????? ??? ???????? ??? ?????? ????? ????? ???????.Energy is needed to overcome the attractive forces and give the particles increased kinetic energy of vibration. ?????? ?? ??? ?????? ???? ?????? ??? ??? ??????? ?????? ???? ?????? ????????.Freezing (liquid to solid)?????? (?? ?????? ??????? ?????? ??????)On cooling, liquid particles lose kinetic energy and so can become more strongly attracted to each other. ?? ???? ??????? ???? ???????? ?????? ??????? ????? ????? ??? ??????? ???? ??????? ???????? ?? ????? ?????.Eventually at the freezing point the forces of attraction are sufficient to remove any remaining freedom and the particles come together to form the ordered solid arrangement. ???? ?????? ????? ?????? ???? ??? ??????? ????? ?????? ?? ???? ???? ???????? ????? ?????? ?? ??? ????? ?????? ?????? ??????.-32119220733541922702063751873885209550+1045845-2540Thermal expansion?????? ???????27.3Thermal expansion of liquids?????? ??????? ??????? . 5286375278765If you take a large glass flask which has a stopper with a long open-ended glass tube, and you heat the flask gently, what would happen????? ????? ??? ???? ???? ????? ????? ??? ????? ??????? ?????? ?????? ????? ??????? ?? ??? ?????? ?????? ????. You will observe that the liquid will rise in the tube. ??? ????? ?? ?????? ?? ????? ?? ???????? Thermal expansion of solids ?????? ??????? ?????? ?????? Activity-790575149860266702540 1- If you pass the brass metal ball through the ring, what would happen?1- ???? ???? ???? ?????? ???????? ??? ?????? ?? ???????The metal ball will pass easily. ????? ???????? ??? ??? ??????.2- If you hold metal ball above flame and heat for a minute and try to put the heated metal ball through the ring, what would happen?2- ???? ???? ????? ???????? ??? ??????? ???? ????? ?? ?????? ??????? ?? ??????? The metal ball won’t pass through the ring. ????? ???????? ?? ???.3- If you put the heated metal ball in the beaker with the cold water and put the cooled metal ball through the ring again, what would happen?3- ???? ???? ??? ???? ????? ???????? ?? ??? ??? ??? ???? ?? ??? ?????? ????? ??????? ???? ?????? ?The metal ball will pass easily again . ????? ???????? ??? ??? ??? ????Why matter expands when it is heated? ????? ????? ?????? ??? ???????? Thermal expansion of the liquid and the solid can be explained using the kinetic particle model. ???? ????? ?????? ??????? ?? ??????? ??????? ?????? ???????? ????? ?????? ????????.The kinetic particle model explains thermal expansion as follows. If a matter is heated, its particles speed up. Their vibrations take up more space, so the matter expands slightly in all directions. If the temperature falls, the reverse happens and the material contracts (gets smaller).???? ????? ?????? ???????? ?????? ??????? ??? ???. ??? ????? ???? ??? ?????? ???? ????????. ????? ???????? ????????? ??? ?????? ????? ????? ?????? ??????? ?? ?? ?????????. ??? ?????? ???? ??????? ???? ????? ??? ????? ??????. Comparing expansion ?????? ?????? Different materials expand by different amounts for the same rise in temperature. When choosing materials for particular jobs, it can be important to know how much they will expand.????? ?????? ???????? ??????? ?????? ??? ??? ???? ???????? ???? ?? ????? ????? ????? ???? ?????? ??? ?????? ?????? ?????? ?????. Steel rods can be used to reinforce concrete because both materials expand equally. ?????? ????? ????? ?????? ??????? ?????? ??????? ???? ???????. 4781550200025If an ordinary glass dish is put straight into a hot oven, it cracks, but Pyrex wouldn’t crack because it expands much less than ordinary glass.??? ??? ?????? ?????? ?? ??? ???? ???? ????? ? ??? ??? ??? ????????? ?? ????? ??? ????? ??? ?? ???? ?????? ??????. Thermal expansion can be a problem?????? ??????? ???? ?????-361950582930Why gaps are left at the end of bridges? ????? ???? ?????? ??? ????? ???????Expansion gaps are left to prevent buckling or cracking as temperature changes.???? ???????? ???? ?????? ??????? ?? ??????.-466725125730Why overhead cables are left slack when they suspended from poles?????? ???? ???????? ?????? ??? ??????? ??? ????????To allow for the contraction that would happen on a very cold day. ??? ?????? ???????? ???? ?????? ???????.Importance of thermal expansion????? ?????? ???????Thermal expansion has many useful applications in our daily life such as thermometer and thermostat.?????? ??????? ?? ??????? ????? ????? ?? ?????? ??? ????????? ???????????.Thermometer:?????????4819650114935The liquid in the bulb expands when the temperature rises. ?????? ??????? ???? ???????? ???????? ????????? ????? ??? ?????? ???? ???????.Bimetallic strip:?????? ????? ??????4419600120650Bimetal strip consist of two different metals are bonded together. When heated, one metal expand more than the other, which makes the bimetal strip bend. Bimetal strips are used in some thermostats devices for keeping a steady temperature.?????? ????? ?????? ????? ?? ??????? ??????? ?????? ???. ??? ????? ?????? ????? ?????? ? ??? ???????? ????? ???? ?? ????? ? ??? ???? ?????? ????? ?????? ?????.?????? ?????? ????? ?????? ?? ??? ????? ?????????? ???? ???? ??????? ??? ???? ????? ?????.479107535560Heating devices and air-conditioning are examples of devices that are thermostatically controlled.?????? ????? ??????? ?????? ??????? ?????????? ?????? ?? ????? ??????? ??? ????? ????. How bimetal thermostats control the temperature???? ???? ?????????? ??? ?????? ????? ???????? The figure below shows thermostat.???? ????? ?????? ?????????? 160972535560 When the temperature rises, the bimetal strip bends, the contacts separate, and the current to the device is cut off. When the temperature falls, the bimetal strip straightens. And the current is switched again. ????? ????? ???? ??????? ????? ?????? ????? ??????? ????? ???????? ?????? ?????? ?? ??????.????? ????? ???? ??????? ? ???? ?????? ???? ?????????. ???? ?????? ??? ??????.4349750-212725Freezing water????? ?????27.5Freezing water can break a container. ???? ????? ???? ?? ???? ?????? ???? ??????. If you fill a bottle with water to the brim and close it firmly. What would happen as the water freezes?453517056515??? ??? ????? ?????? ??? ?????? ???????? ?????. ???? ????? ????? ????? ??????As water freezes, it will crack the container.????? ????? ?????? ????? ??????? ????? ???????.The force of the expansion can break water pipes and split rocks with rainwater trapped in them.??? ???? ?????? ???????? ???? ?? ???? ?????? ?????? ????? ?????? ??? ???? ???? ??????? ???????? ?? ??????. Anomalous expansion of water?????? ????? ????? ??? ?????? ????? ?????? ?????? According to the kinetic particle model, a liquid gradually contract as it cools, solidify with negligible change in volume, and continue to contract after freezing. ???? ?????? ?????? ???????? ? ?? ???? ????? ??? ?????? ?????? ?? ???????? ??? ????? ??? ???? ???? ?? ????.466090045720Water is unusual in that it expands on freezing . The volume of water increases when the temperature decreases from 4 C to 0 C. The volume of water is minimum at 4 C, therefore its density will be maximum at 4 C.????? ??? ?? ???? ??????? ??? ??? ????? ??? ?????. ?????? ??? ????? ????? ????? ???? ??????? ?? 4 ???? ????? ??? ??? ???? ????? . ???? ???? ??? ??? ????? ??? ???? 4 ???? ????? ????? ????? ????? ???? ?? ???? ??? ???? 4 ???? ?????. Why water expands as it freezes?????? ????? ????? ??? ??????In liquid water, the water molecules are close together. But in ice, the molecules linkup in a very open structure which takes more space than in liquid.?? ????? ?????? ?????? ????? ????? ?? ????? ?????. ???? ?? ?????? ???? ???????? ?? ???? ?????? ??? ????? ???? ?? ???????? ???? ????? ???? ??? ???? ???? ?? ??????.2921028575335724528575 ???????? Molecules in water Molecules in iceWhat are the effects of anomalous expansion of water??? ?? ?????? ???????? ??? ?????? ????? ??????71818598425In a lake or sea, as water is cooled from, higher temperature to 4 it becomes denser and sinks to the bottom but as it cools from 4 to freezing point, its density reduces as it expands and it rises to the top and eventually forms ice. The floating ice acts as insulation preventing the freezing of water below it, ensuring that life survives. So fishes and aquatic life survives due to anomalous nature of water, ice being lighter than water floats and insulates the water below it from freezing.?? ??????? ?? ????? ? ??? ???? ????? ?? ????? ????? ????? ??? ???? 4 ???? ????? ?????? ???? ????? ??? ??? ?????? ???? ???? ????? 4 ????? ??? ???? .?????? ???? ???? ?? 4 ???? ????? ??? ???? ??????? ????? ????? ?????? ???? ????? ?????? ?????? ??? ???? ?????? ?????? ??? ??? ??????? . ?????? ?????? ???? ????? ????? ???? ????? ????? ????? ?????? ?????? ??????? ??????.???? ??????? ???????? ??????? ??? ??? ?????? ???? ?????? ????? ????? ??????? ??? ?? ?????? ??? ?? ????? ???? ????? ????? ???? ?? ??????.62674517208527.6Density???????Is lead heavier than water? ?? ?????? ???? ?? ??????Not necessary. It depends on the volumes of lead and water being compared. However, lead is more dense than water: it has more kilograms packed into every cubic meter.?????? ???? ????? ?? ?????: ?? ?? ?????? ???? ?????? ???? ????? ?? ?? ??? ????.Density is a measure of the amount of mass in a certain volume.This physical property is often used to identify and classify substances.??????? ?? ????? ????? ?????? ?? ??? ????.?????? ?? ?????? ??? ??????? ?????????? ?????? ?????? ??????.It is often represented by the Greek letter ρ (rho).??????? ?? ?????? ?????? ???????? (ρ)The density of a material is calculated like this:????? ???? ????? ?????? ?? ???? ??????? ???????:where:ρ (rho) is the density, m is the mass, V is the volume.??? (ρ) ?? ???????? ?(m) ?? ??????? ?(V) ?? ?????.The SI unit of density is kilograms per cubic meter (kg/m3).It is usually expressed in grams per cubic centimeters, or g/cm3.???? ?????? ?????? ??????? ?? ???? ???? ??? ??? ???? (kg/m3)????? ??????? ?? ??????? ???? ????? ???????? ??? ??????? ???? (g/cm3)Substanceρ (kg/m3)Hydrogen0.0899Helium0.179Steam(100°C) 0.598Air1.29Oxygen1.43Carbon dioxide1.98Ethanol0.806 × 103Ice0.917 × 103Fresh water(4°C) 1.00 × 103Sea water(15°C) 1.025 × 103Iron7.86 × 103Mercury13.6 × 103Gold19.3 × 103The chart lists the densities of some common materials.?????? ??? ?????? ??? ?????? ???????.318706540640Notes:Gases have much lower densities than solids or liquids.??????? ??? ????? ?? ?????? ?????? ?? ???????.Density is the key to floating. Ice is less dense than water. This explains why icebergs float in the sea, rather than sinking to the bottom.??????? ?? ????? ?????. ????? ??? ????? ?? ?????. ???? ?? ???? ????? ???? ???? ?????? ?? ?????? ???? ?? ????? ??? ????.Many materials have a range of densities. Some types of wood, for example, are less dense than water and will float. Others (such as mahogany) are more dense and sink. The density depends on the composition.???? ?? ?????? ????? ??? ????????. ??? ????? ?????? ??? ???? ??????? ??? ????? ?? ????? ?????. ???? ?? ???? ????? ?????. ?? ?? ??????? ????? ??? ??????? ?? ????????.Gold is denser than silver. Pure gold is a soft metal, so jewelers add silver to make it harder. The amount of silver added can be judged by measuring the density.????? ???? ????? ?? ?????. ????? ?????? ?? ???? ???? ??? ?????? ????? ????????? ?????? ????. ???? ????? ??????? ???? ?? ?????? ?? ????? ???????.It is useful to remember that the density of water is 1000 kg/m3, 1.0 g/cm3 or 1 kg/liter.?? ?????? ?? ????? ?? ????? ?????: (1000 kg/m3, 1.0 g/cm3 or 1 kg/liter).-268605-447040Examples :1- You have found a metal that has a mass of 5.8 g and a volume of 2.9 cm3. What is the density of this metal??????? ???? ????? (5.8 g)? ????? (2.9 cm3). ?? ????? ???????A liquid has a density of 1.54 g/mL. What is the mass of 5.00 mL of this liquid????? ?????? (1.54 g/mL)? ?? ?? ???? (5.00 mL) ?? ??? ???????A block of vanadium metal has a density of 5.96 g/mL. What is the volume of 10.0 g of metal????? ?? ???? ????????? ??? ????? (5.96 g/mL). ?? ?? ??? (10.0 g) ?? ???????Measuring density???? ???????It easy to calculate density of a regular solid, but we have to use other methods when we have an irregular solid or even a liquid or a gas.?? ????? ???? ????? ?????? ?????? ???????? ?? ?????? ???? ????? ?? ?????? ?????? ???? ????? ???? ????? ???? ???? ??? ?????? ?? ????? ?? ???? ????? ?? ??? ?????.How do you find the density of a regular solids???? ??? ????? ???? ???? ?????? ?? ??????Find the Mass of the solid on a balance.??? ???? ?????? ?????? ?? ???? ???????.Measure the three lengths and calculate the Volume.(i.e. )??? ???? ????? ??????? ????? ?????.Calculate the Density.???? ???????.How do you find the density of an irregular solids???? ??? ????? ???? ???? ??? ?????? ?? ??????Find the Mass of the solid on a balance.??? ???? ?????? ?????? ?? ???? ???????.Fill the Measuring Cylinder with Water to a known Volume.???? ??????? ????????? ?????? ??? ??? ?????.Add the Object.???? ????? ?????? ???? ??????.Work out the Volume of Water that is displaced.???? ??? ????? ?????? ?? ???? ????? ?? ???????.Calculate the Density.???? ???????.Other method to find the density of an irregular solids:????? ???? ?????? ????? ???? ???? ??? ?????? ?? ??????Find the mass of the solid on a balance.??? ???? ?????? ?????? ?? ???? ???????Add water until just overflowing.???? ????? ??? ????.Place a Measuring Cylinder under the spout.??? ??????? ?????? ??? ???? ??????.Add the Object.???? ????? ?????? ???? ??????.Collect the Water and read off the Volume.???? ????? ????? ????.Calculate Density.???? ???????.How do you find the density of liquids???? ??? ????? ???? ??????Find the Mass of an empty Measuring Cylinder.??? ???? ????? ??????? ????.Add a certain Volume of Liquid.???? ??? ???? ?? ??????.Find the Mass of the Measuring Cylinder and Liquid??? ???? ??????? ????????? ?? ??????Calculate the Mass of Liquid . ???? ???? ??????.(Mass of Liquid = Mass of Measuring Cylinder and Liquid – Mass of empty Measuring Cylinder)(???? ?????? = ???? ??????? ????????? ?? ?????? - ???? ??????? ????????? ??????)Calculate Density of Liquid.???? ????? ??????.How do you find the density of gases???? ??? ????? ???? ????????? ??? ????? ???? ??????Remove the air from a flask of a known Volume, using a vacuum pump.????? ?????? ?? ?????? ?????? ?????? ???????? ???? ???????.Find its Mass.??? ???? ????????.Add the gas to be tested.????? ?????.Re-find its mass.??? ???? ???????? ?? ????? ???? ???? .The difference is the Mass of gas.???? ????? ?????? ???? ?????.Calculate Density.???? ???????.-5232401887220Problem:Estimate (1) the mass of water in a swimming pool and (2) the total mass of air in all the rooms of your home.???? (1) ???? ????? ?? ???? ?????? ?(2) ?????? ??????? ?????? ?? ?? ??? ?????.27.7Pressure ?????3890010282575The effect that a force has when it acts on a surface depends on two things: the size of the force and the area that it is pressing on. We measure this as pressure.Pressure is the force (or thrust) acting on unitarea (i.e. 1m2) and is calculated from: ?? ??? ????? ??? ??? ?? ????? ??? ????? ??? ????? ?????? ????? ???? ???? ???? ??? ????? . ????? ???? ????? ????? ???? ???? ????? ??????? ??? ???? ???????.-4508538735 (F) force is measured in Newton (N) and(A) area in square meters (m2), (P)pressure is measured in Newton/square meter (N/m2). 1N/m2 is called 1 Pascal (Pa): ????? ???? ???????? . ???????? ???? ?????? ??????. ????? ????? ????? ?????/ ??? ???? ????? ???? ?????? (Pa)-595630435610Examples:2981325219075-381000314325Increasing the pressure by reducing the area???? ??? ????? ???? ????? ????? ????? ??? ?????? ??? ????? ??? ???? ????? ???? ????? ?????.????? ????? ????? ?????? ???? ????? ??? ????? ????? ?? ????? ????? ???? ??? ??? ?????????. -2667002190753162300219075 Reducing the pressure by increasing the area???? ????? ????? ??? ????? ????? ?????? ????? ?????? ??? ????? ??? ???? ???? ?????.???? ?????? ??????? ??? ????? ????? ????? ?????? ????? ??? ????? ???????? ?? ???? ?????? ???? ?????348488079375-669925180975Question:The wind pressure on the wall on the right is 100 Pa. If the wall has an area of 6 m2, what is the force on it????? ?????? ???? ????? 100Pa??? ???? ?????? 6m2. ?? ????? ??? ?????? ??????? ??? ???????Solution: Pressure in liquids????? ?? ???????A liquid is held in its container by its weight. This causes pressure on thecontainer, and pressure on any object in the liquid. The following properties apply to any stationary liquid in an open container.4558665488315??? ?????? ?? ?????? ???? ???? ??? ?????? ???? ?? ??? ????? .?????? ???? ????? ????? ????? ???? ????1- Pressure at one depth acts equally in all directions. The can of water in Figure has similar holes all round it at the same level. Water comes out equally fast and equally far from each hole. Hence the pressure exerted by the water at this depth is the same in all directions. 1- ????? ??? ??? ???? ?????? ?? ???? ?????????.3750945278765????? ???? ???? ????? ???? ?????? ???? ??? ????? ?? ???? ??????? ???? ??? ???????2- Pressure in a liquid increases with depth.The pressure in the liquid is not the same at all depths. It is small just under the surface but increases as you go deeper. This can be shown by drilling small holes in the container as shown in the diagram opposite. The top jet does not travel as far as the jets from the holes below because the pressure is not so large. Notice that the direction of the pressure causing the jets of liquid is outwards.Dams are made thicker at the bottom to withstand the higher pressure there. - ????? ????? ?????? ?????.2???? ????? ????? ???? ??? ?????? ?????? ?????? ?????. ?????? ???? ???? ?????? ??????? ???? ?????? ?????.ActivityPRESSURE INCREASES WITH DEPTH, IS IT A LINEAR RELATIONSHIP?421894043815-128034-1572555Here is an activity to measure the increase of pressure with the height of a liquid:Build the set up for a lab ! ?Is there a linear relationship between the depth of the funnel and the height of water in the U- tube? Build a table. X = depth in cm of the funnel = independent variable Y = height of rising water in the U-tube = dependent variable. Plots The dots (X,Y) on a graph paper and see if you have a relationships between the variables.)?????? ?????? ?? ????? ????? ?????? ??? ?????? . ??? ??? ?????? ?????? ?? ???? ?????? ??? ??? ????? ???? ?????? ??????? ????? ?? ??????? U ???? ??????? ?????? ??????? ??????? ??????Depth (cm) of the funnelHeight of rising water954405100203034563051968503- Pressure depends on the density of the liquid.Dense liquids have a greater weight for the same volume so they press down on the container with greater pressure. The diagram compares the pressure at the bottom of a beaker of water with the pressure at the bottom of a beaker of the liquid metal mercury.3- ????? ????? ??? ????? ??????.??????? ??????? ????? ???? ?? ??????? ????? ????? ???? ??? ?????? ???????? ????? ????? ?? ?????? ?? ??????? ?????.4- Pressure doesn’t depend on the shape of the container.310451531750It may seem surprising but the pressure in a liquid does not depend on the shape of the container. Thediagram below shows four different ‘containers’ joined together. When you pour in a liquid it rises to the same level in each section. This proves that the pressures at points A, B, C, and D are the same.4- ?? ????? ????? ??? ??? ??????.????? ???? ????? ????? ?????? ?????? ??????? ???? ??? ??????? ?? ?? ???? . ??? ???? ?? ????? ??? ?? ?????? A,B,C,D ?? ???? ????? ??? ??? ??? ?????.Calculating the pressure in a liquid.???? ????? ???? ?????? 3569970139700The container on the right has a base area A. It is filled to a depth h with a liquid of density ρ (Greek letter ‘rho’). To calculate the pressure on the base due to the liquid, you first need to know the weight of the liquid on it:volume of liquid = base area x depth = Ahmass of liquid = density X volume = ρ Ahweight of liquid = mass x g = ρgAh(g = 10N/kg)So: force on base = ρgAhThis force is acting on an area A.So: Pressure=forcearea=ρgAhA=ρghAt a depth h in a liquid of density ρ:-565785344170 Pressure P = ρgh???? ??? ?? ???? ??????? ??????? ??????? ????? (??????? ??????)Question:If the density of water is 1000 kg/m3, what is the pressure due to the water at the bottom of a swimming pool 2 m deep???? ???? ????? ????? ????? 1000kg/m3?? ????? ????? ???? ???? ?? ????? ??? ??? ???? ????? ????? 2m?27.8Hydraulic systems Liquids are very difficult to compress because their particles are very close together. If you apply a force to the surface of a liquid which is trapped inside a container, then the pressure is transmitted throughout the liquidBlaise Pascal (1623-1662), a French physician, discovered that any change in pressure applied at any point on a confined fluid is transmitted undiminished throughout the fluid this fact became known as Pascal's principleWhen fluids are used in machines, such as hydraulic lifts, to multiply forces, Pascal's principle is being applied. ???? ????? ?? ??? ??????? ???? ?????? ???????? .( ?????? ?????? ??? ???? ???? ??? ??? ?? ?? ???? ?? ????? ????? ????? ????? ?????? ??? ???? ????? ??????). ??? ??????? ??????? ?? ?????? ???????????? ?????? ????? ??? ???? ?????? ????. In a hydraulic system,39731950a fluid is confined to two connecting chambers, as shown in Figure. Each chamber has a piston that is free to move. If a force FI, is exerted on the first piston with a surface area of AI' the pressure (p) exerted on the fluid can be determined by using the following equation.P1=F1A1According to Pascal's principle, pressure is transmitted without change throughout a fluid, and therefore, the pressure exerted by the fluid on the second piston, with a surface area A2' can also be determined.P2=F2A2Because the pressure P2 is equal in value to PI' you can determine the force exerted by the hydraulic lift. BecauseF1/A1 = F2/A2,then the force exerted by the second piston is shown by the following equation.Force exerted by Hidraulic Lift F2= F1A2A1Hydraulic jack ??????? ???????????? A load is easier to lift if you use a jack. The diagram shows a simple hydraulic jack. A downward force on the input piston puts pressure on the oil. The pressure is transmitted by the oil. It produces a larger upward force on the output piston.The calculation of output force assumes that the jack is frictionless.Force exerted by Hidraulic jack F2= F1A2A1208915309245 In a real jack, there is friction to overcome. This reduces the output force.??? ???? ??? ??? ???? ?? ???? ??? ????? ??? ?? ???? ?????? ????? ??? ????? ??? ????? ??????? ??? ?????? ??????? ??? ????? ??? ?????? ?????? ??? ???? ??? ????? ??? ?????? ??????.-420370-499110Question:The diagram on the right shows a simple hydraulic jack. ?? ????? ?????? ?????????? Assuming that the jack is frictionless: ????? ?? ???????? ????? ???? a) What is the pressure at A? A ????? ??? b) What is the pressure at B? B ????? ??? c) What is the output force? B ????? ??????? ???82613590170Solution:Other examples of Hydraulic system.Hydraulic car brakes ??????? ???????????? 3474720488951-Hydraulic forces are used in the disc brakes of cars and motor bikes. 2-A steel disc is fixed to the centre of each wheel. 3- As the wheel turns, the disc spins between two brake pads. 4- When the brake is applied, a piston in the master cylinder presses on the brake fluid.5- A thick, strong pipe connects the master cylinder with slave cylinders on each side of the disc.6- The hydraulic pressure is transferred to the pistons in the slave cylinders. These force the brake pads on to the disc. Friction then slows the wheel down.??? ????? ??? ??????? ????? ????? ??? ?????? ?? ????????? ???????? ???? ?????? ??? ????? ??? ???? ????????? ??? ????? ????? . ???? ???? ????? ??????? ??? ????? ????? ???????? ????? ???????? ??? ????? ??????Hydraulic press (Excavator) ??????? ???????????? A hydraulic press is used for compressing (squashing) things. It is like a hydraulic jack, but with a metal plate fixed rigidly above the output piston, so that the gap closes as the piston moves upwards.???? ??????? ??????????? ???? ????? ??? ????? ?????? ????? ?????? ??? ?????? ?????? ???? ???? ?????? ??? ????? ?????? ?????.10928352540Buoyancy?????27.9-285750280670Why is it so hard to put a beach ball under water while a piece of small steel sinks in the water?????? ?? ????? ?? ??? ??? ?????? ??? ????? ????? ???? ???? ????? ?? ???????The water exerts force on an object immersed in the water. This force is called Buoyant force. ??? ????? ???? ??? ??? ??? ????? ??????? ?? ?????. ??? ????? ???? ??? ?????. Buoyancy explains why objects float. Buoyancy is a measure of the upward force a fluid exerts on an object that is submerged.????? ?? ????? ????? ??????? ????? ???? ?????? ???? ??? ???? ????? ???????The buoyant force works opposite the weight of an object.???? ??? ????? ?? ??? ????? ??? ?????4371975195580The water in the pool exerts an upward force that acts in a direction opposite to the boy’s weight.????? ?? ?????? ????? ??? ????? ???? ???? ??? ????? ??? ?????.The strength of the buoyant force on an object in water depends on the volume of the object that is underwater.??? ??? ??? ????? ??? ???? ?? ????? ?????? ??? ???? ?????? ???? ??? ?????. As you keep pushing downward on the ball, the buoyant force gets stronger and stronger???? ????? ???? ????? ?????? ???? ??? ????? ???? ?????4086225343535The greater pressure at greater depths means the net force is greatest pushing upward on a submerged object???? ????? ????? ??? ??? ???? ???? ?? ????? ????? ???? ???? ?? ??? ????? ??????? ????? All fluids exert pressure: the amount of force exerted per unit area of a surface.?? ??????? ???? ??? :???? ????? ???????? ??? ???? ??????? ?? ?????How does the Buoyant force work???? ???? ??? ?????? 4371975151130Archimedes’ principle???? ???????The magnitude of the buoyant force acting on a submerged object is equal to the weight of the fluid the object displaces.????? ??? ????? ????? ??? ?????? ?????? ?????? ????? ???????3790950314960-628650-1167130-476250123190Practice Lab: Archimedes’ principle ???? ??????? 24366-273345Purpose:We are doing this experiment to prove Archimedes' principle. (When a body is wholly or partly submerged in a fluid the buoyant force equals the weight of fluid displaced)????? ????? ???? ???????(??? ??? ??? ???? ?? ????? ?? ???? ??? ??? ??? ?????? ???? ??? ?????? ??????) Notice1-A fluid means either a liquid or a gas. ?????? ???? ???? ?? ??? 2-The increase of pressure with depth has an important consequence. It allows you to swim. That is, it creates an upward force, called the buoyant force, on all objects. By comparing the buoyant force on an object with its weight, you will know if the object will sink or float.Use the key words (spring balance, weight, buoyant force, eureka can, and displaced water) and the figure to set up the experiment.?????? ???????( ??????? ????????, ?????, ??? ??? ??????, ???? ?????, ????? ??????) ????? ????? ?????? ????? ??????? ?? ???? ????? ??? ????? ????? ???????. Use the space below to write step by step procedure of the experiment, to carry it out successfully.533400133350 Part One1- The mass of empty beaker m1 =……….kg.???? ?????? ???? 2- The weight of the block hanging from the spring balance (real weight) Fg = ………N.????? ??????? ????? ?? ???? ??????? ???????? 3- The weight of the block when it is completely immersed in water (apparent weight) F'g =………N.????? ??????? ????? ??? ???? ?????? 4- The upthrust of the water on the block (buoyant force) Fb = Fg - F'g =…………N. ??? ??? ????? ?? ???? ??????? ??????? 5- The mass of beaker with water m2 =……………..kg.???? ?????? ?? ????? ?????? 6- The mass of displaced water m = m1 –m2 =……………kg.???? ????? ??????7- The weight of displaced water = m.g =……x 9.8 =……….N ??? ????? ??????8- When you compare between buoyant force Fb and the weight of displaced water m what do you see: ……………………………????? ????? ??? ??? ??? ????? ???? ????? ?????? ???? ??????9- Write your conclusion based on your observations ???? ???????? ???????????Part Two1- The volume of displaced water Vw = ………m3??? ????? ?????? 2- The volume of the block Vs = …….m3 ??? ????? 3- The mass of displaced water m = ρ Vw = ρ Vs = …………… (ρw = 1000 kg/m3) ?????? ??????? ????? ???? ????? ?????? 4- The weight of displaced water = mg = ……. x ………. x g5- Fb =…………….N. Part Three (prove Archimedes' principle mathematically).3200400114300Suppose that a box is immersed in water. It has a height (L), and its top and bottom each have surface area A. Its volume, then, is(V = L A). Water pressure exerts forces on all sides, as shown in Figure. Will the box sink or float? As you know, the pressure on the box depends on its depth (h) to find out if the box will float in the water, you will need to determine how the pressure on the top of the box compares with the pressure from below the box. Compare these two equations.Ftop = Ptop . A =…………..Fbottom = Pbottom . A =………On the four vertical sides, the forces are equal in all directions, so there is no net horizontal force. The upward force on the bottom is larger than the downward force on the top, so there is a net upward Force. The buoyant force can now be determined.??????? ??????? ?????? Fbuoyant = Fbottom _ Ftop =……………………… =……………………. Fb =……………………write your conclusion ???? ???????? ??? ????? ???? ??????? ????? ??????? Part Four (Sink or float?)What are the forces that act on an object that is placed in a fluid? 1- One force is the …………………………………on the object. 2- There is also the …………………………………of the object.?? ????? ??????? ??? ??? ????? ?? ???? The difference between the buoyant force and the object's weight determines whether an object sinks or floats.????? ??? ??? ??? ?????? ???? ?????? ???? ?? ??? ????? ???? ?? ???? ?? ??????Suppose you submerge three items in a tank filled with water (ρ water = 1.00 X 103 kg/m3). They all have the same volume =1.00 X 10-4 m3.????? ???? ????? ????? ?? ????? ??? ??? ????? ?????? ????? ?????? ???? ????? ?????? ??????. One item is an ice cube with a mass of 0.090 kg.How will each item move in the water?Fbuoyant = ………………Fg = ………………… Compare Fbuoyant and Fg The second is aluminum can of soda with a mass of 0.100 kg. -64770181610 Fbuoyant = …………………..Fg = …………………Compare Fbuoyant and FgThe third is a block of steel with a mass of 0.90 kg. -33655183515Fbuoyant = ………………..Fg = …………………Compare Fbuoyant and FgThe result the ice cube will ……. Because …………………………….………………………………The result the aluminum can will ……. Because …………………………….……………………………..The result the block of steel will ……. Because …………………………….…………………………….search for Archimedes' principle story and read it to your group.search for some applications used Archimedes' principle.???? ?? ??? ???? ??????? ?????? ??????? ???? ?? ??? ??????? ???? ??????? Questions-510806-1918291- There are 3 syringes filled with air, water, and sand. Students compressed the syringes of each and found the following results: ???? ????? ?? ?????? ?????? ?????? ?? ???? ????? ?????? ??? ?????? ?????? ?????? ??????? ????????? ?????? ?????? ?????? ???????:47625304800???? ?????? ?????? ??? ?????? ?? ???????CompressibleNot compressibleAirWaterSand a. Which two substances were not compressible? ?? ?????? ?? ????? ????????? ___________ and _______________b. Make a hypothesis for this experiment. ???? ??????? ?????? ??? ???? ??? ??????? ____________________________________________________________________________________________________________________________________________________________________________________2-When a substance changes state (for example from liquid to solid by freezing), does its volume change? Explain this in terms of the particle model.??? ???? ???? ?? ?????? ??????? ??? ?????? ?????? ???????? ?? ????? ????? ????? ???? ??? ?? ??? ??????? ??????? ??????.3- When a substance changes state (for example from liquid to solid by freezing), does its mass (or weight) change? Explain this in terms of the particle model.??? ???? ???? ?? ?????? ??????? ??? ?????? ?????? ???????? ?? ????? ?????? ????? ???? ??? ?? ??? ??????? ??????? ??????.4- How does the surface area of a body of water effect the rate of evaporation? How can this be explained using the particle model????? ??? ???? ????? ????? ????? ?? ???? ?????? ?? ??? ??????? ??????? ???????5- What happens to metal when it is heated up? What happens when it is cooled down? What are the particles in these solids doing in each case????? ???? ?????? ?????? ??? ?? ???????? ????? ???? ??? ???????? ????? ???? ???????? ?? ?? ?????6- Explain what would happen if aluminium rods are used to reinforce concrete.???? ?? ??? ???? ??? ??????? ????? ????????? ?????? ???????.7-If overhead power cables are hung from pylons during the day, it is important that the cables are left slack. By considering what happens to the temperature at night, explain what would happen if the cables were pulled tight during the day.??? ???? ??????? ?????????? ?? ?????? ????? ???? ??????. ??????? ?? ???? ????? ??????? ????? ???? ???????? ????? ?????? ???????? ?? ???? ??????? ??? ???? ????? ?? ??????.8- What is the density of a billiard ball that has a volume of 100 cm3 and a mass of 250 g??? ?? ????? ??? ????????? ???? ??? ??? (100 cm3) ????? (250 g)?9- A loaf of bread has a volume of 2270 cm3 and a mass of 454 g. What is the density of the bread????? ?? ????? ?? ??? (2270 cm3)? ????? ?? (454 g). ?? ?? ????? ??????10- A liter of water has a mass of 1000 g. What is the density of water? (Hint: 1 mL = 1 cm3)??? ???? ?? ????? ?? ???? (1000 g) ?? ?? ????? ??????11- A block of wood has a density of 0.6 g/cm3 and a volume of 1.2 cm3. What is the mass of the block of wood? Be careful!???? ?? ????? ??? ????? (0.6 g/cm3)? ???? (1.2 cm3). ?? ?? ???? ???? ??????12- Estimate (1) the mass of water in a swimming pool and (2) the total mass of air in all the rooms of your home.???? (1) ???? ????? ?? ???? ?????? ?(2) ?????? ??????? ?????? ?? ?? ??? ?????.13- The diagram shows an Inuit fisherman walking across soft snow.79057566675Explain why he is wearing snow-shoes. Use the following words in your answer: Force weight pressure area sink????? ???? ???? ??? ??? ??? ??? ???? , ??? ????? ???? ?????? ???? ????? ??????? ??????? ???????.14- A tank for storing liquid has a base of area 1.5 m2. What is the pressure on the base of the tank when it contains:a) water weighing 6000 Nb) oil weighing 4500 N????? ????? ?????? 1.5 m2 ????? ???? . ?? ????? ????? ?????? ??? ??????? ????? ??????- ??? ???? 6000N ?- ??? ???? 4500N 15- What is the pressure 100m below the surface of sea water of density 1150kg/m3??? ????? ????? ??? ??? ????? ??? ???? ????? ?????393382524130016- g = 10 N/kg; density of water = 1000kgfm3; density of paraffin = 800 kg/m3In the diagram on the right:?? ????? a) How does the pressure at A compare with the pressure at B? B ??????? ? A??? ???? ????? ??? b) How does the pressure at B compare with the pressure at D? D ??????? ? B??? ???? ????? ??c) How does the pressure at A compare with the pressure at C? C ??????? ? A??? ???? ????? ??d) If the water in the system were replaced with paraffin, how would this affect the pressure at B? ??? ?????? ????? ????? ???????? .??? ???? ??? ??? ????? ??? B 17- A rectangular storage tank 4m long by 3m wide is filled with paraffin to a depth of 2 m. Calculate: ???? ??? ??? ?????? ???????? ???? 4 ??? ????3 ??? ???? 2 ??? ????? ?????????. ??????? ????????? a) the volume of paraffin. b) the mass of paraffin. ???? ?????????c) the weight of paraffin. ??? ?????????d) the pressure at the bottom of the tank due to the paraffin????? ?????? ??? ??? ?????? ?? ?????????.3- In the diagram on the right, calculate the pressure at B due to the water.?? ????? ???? ????? ??? B 18- In a hydraulic press a force of 20N is applied to a piston of area 0.20 m2. The area of the other piston is 2.0 m2. What isa- the pressure transmitted through the liquid,b- the force on the other piston????? ??? ?????????? ???? 20N ??? ???? ?????? 0.20m2 . ???? ???? ????? ?????? ????? ????? 2m2 . ??? ????? ?- ????? ?????? ???? ??????.?- ????? ??????? ?? ?????? ??????. 19- Dentists' chairs are examples of hydraulic-lift systems. If a chair weighs1600 N and rests on a piston with a cross-section area of 1440 cm2, what force must be applied to the smaller piston with a cross-sectional area of 72 cm2 to lift the chair?????? ???? ???? ??????? ????? ??????? ????????????. ??? ??? ??? ??????1600N ????? ????? ????? ????? 1440cm2. ??? ????? ????? ?????? ??????? ??? ?????? ?????? ???? ????? ????? 72cm2 ?20- Archimedes' principle states that __________.A) the buoyant force on an object is greater than the weight of the fluid it displaces B) when the speed of a fluid increases, the pressure exerted by the fluid decreases C) the buoyant force on an object is equal to the weight of the fluid it displaces D) pressure applied to a fluid is transmitted unchanged throughout the fluid21- An object weighing 50 kg is floating in a fluid. What is the buoyant force of the fluid on the object?A) > 50 kg B) 50 kg C) < 50 kg D) Not enough information is given.22- If a cube is submerged in water, where on the cube is the pressure exerted by the water the greatest?A) on the bottom B) The pressure is equal on all sides of a cube. C) on the sides D) on the top23- The supporting force exerted by a fluid on an object immersed in it is called __________.A) viscosity B) density C) lift D) buoyant forceResources:Books: 1- Complete physics (Stephen Pople)2- Physics first (George Bethell & David Coppock)3- GCSE Physics ( Tom Duncan & Heather Kennett) 4-Glencoe Physics (Paul W .Zitzewitz)5- The World of Physics (John Avison)6- Cambridge IGCSE Physics (David Sang)Websites:?? ???? ................
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