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Chapter 5 Thermal Energy and Work (pages 176 - 219 in your text) Chapter 5.3 Potential Energy (pages 205 - 216) HYPERLINK "" Mr Bill Nye!!!There are 2 forms of energy:Potential Energy – stored energy of condition or position.Kinetic Energy – energy of motion.Forms of Potential Energy:Elastic energy (springs, rubber bands).Chemical energy (explosives, food).Nuclear energy (sun, reactors).Gravitational energy (hydro dams, clock weights).Units of Measurement:All forms of energy share the same units as “work” and that is JOULES, J.They may also appear as Nm or kgm2/s2.Potential Energy due to Gravity:The energy of an object raised away from the Earth’s center depends on three variables:1. The mass of the object.2. The gravitational pull of the Earth.3. How high the object is above the surface of the Earth.Formula for determining Potential Energy due to Gravity: Eg = mgh where:“Eg” is potential energy due to gravity in Joules, kg m2/s2“m” is mass in kilograms, kg“g” is acceleration due to gravity in m/s2 “h” is the height of the object in meters, m*acceleration due to gravity on Earth is 9.81 m/s2, this is a constant value that is specific to our planet.Ex 1) How much energy is required to raise a 2.00 kg book to a height of 1.5 m?Ex 2) If a 60.0 kg student expends 100 kJ of energy to go up a flight of stairs, how far can she get?Ex 3) At the tarsands, a mechanical shovel can raise a load 15.0 m using 2.70 x 106 J. What is the mass of the load?Ex 4) On a voyage through space, an astronaut stops at a new planet. He notes that it requires 220 J of energy to raise a 20.0 kg metal step 2.40 m on the planet’s surface. What is the acceleration due to gravity on that planet?What to do: Use the GRASP method to complete the problems below. Use the diagram below to answer questions 1 – 4.1. The book in the diagram has a mass of 1.2 kg. If it falls from the shelf to the desk, what is the change in its gravitational potential energy? Does it gain or lose gravitational potential energy?28841701631952. If a student lifts the book from the chair and places it on the desk, how much potential energy does the book gain or lose?3.What is the gravitational potential energy of the book on the desk relative to the floor?4. If a 500 sheet package of paper has a gravitational potential energy of 22 J on the shelf relative to the desk, what is the mass of the paper?5. The acceleration due to gravity on the Moon (gMoon) is 1.64 m/s2. An astronaut is about to climb out of her lunar landing module. She is 2.8 m above the surface of the Moon. If her mass, including her spacesuit, is 71 kg, what is her gravitational potential energy relative to the surface of the Moon?6. Two skiers, with masses of 72 kg and 58 kg, are at the top of a ski hill in the mountains. The altitude at the top is 3782 m. The altitude at a lodge below is 2926 m. How much more gravitational potential energy, relative to the lodge, does the 72 kg skier have than the 58 kg skier? ................
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