Week 2: Measuring Energy Lab - SHAW'S SCIENCE 10



Week 2: Measuring Energy Lab Last Week ReviewLast week we made a rollercoaster to show transformation of energy. Let’s quickly review...Energy is the ability of an object to do work, and is a property that arises from forces (like gravity) that can act upon an object.Potential energy is the stored energy an object has as a result of its condition or position. The roller coaster at the top of the hill has a lot of potential energy because it has the potential for extreme movement when the force of gravity pulls it down the track.Kinetic Energy is the energy of motion. The roller coaster speeding down the hill has a lot of kinetic energy because it is in motion, moving fast down the tracks due to gravity.Energy transformation occurs when potential energy shifts to kinetic or visa versa.Measuring Energy: An IntroductionThe first thing we need to understand about energy is that it is always conserved in a system. Just like matter or atoms in a chemical reaction, energy isn’t created or destroyed but shifted from one form to another.The total amount of energy in a system is the sum of potential energy and kinetic energies. Etotal= PE+KEWhen the roller coaster is at maximum height on the starting hill you built, all of its energy is potential energy, and its kinetic energy is zero. When the roller coaster reached the bottom of your starting hill, with the force of gravity pulling it down the tracks, all of its energy has transformed into kinetic energy, and its potential energy is zero. The sum of the energies stayed the same throughout. This is what we call a closed system. Both potential and kinetic energy can be meausred and quantified. The unit used for energy is the Joule (J).The formula for potential energy is PE=mgh, where..m is the mass of the object in kilograms (kg),g is the gravitational acceleration which on Earth is 9.8 m/s2, (other planets have a weaker or stronger gravitational force and thus the acceleration at which objects move towards the surface of the planet will vary) andh is the height the object is dropped from in meters (m).Example: If an apple has a mass of 0.1 kilograms and is positioned 10 meters off the ground, we can calculate it’s potential energy as PE = (0.1) (9.8) (10) = 9.8 JoulesThe formula for kinetic energy is KE= ? mv2, where...m is mass in kilograms (kg)v is the velocity in meters per second (m/s)Example: The apple from the previous example was dropped and was traveling at a velocity of 14 m/s. So the KE = ? (0.1) (14)2 = 9.8 JoulesNotice that in the apple example used the Kinetic and Potential Energy were equal to one another. Energy was transformed from one kind to anotherand was conserved. So if energy is a closed system, we can assume the potential energy of an object at rest is equal to the kinetic energy of that object in motion:PEinitial=KEfinalKeep this in mind when doing the lab…Try this practice problem. The answer is below the analysis questions to check your work…A hockey puck has a mass of 0.17 kg and is positioned 15 meters above the ground. Calculate it’s Potential Energy Measuring Energy: Laboratory Experiment Big Ideas: Energy is conserved, and its transformation can affect living things and the environment.MaterialsTwo (2) objects of different and knowable massesA measuring tape or other tool to measure heightA cell phone with slow motion video captureA helper to help you record the videoPaper/word document to record data and analysis questions (see template at end of document)A calculator(Optional) A step ladderProcedureBefore Testing:Record a description and the masses of your two objects in kilograms. Mass can be measured using a scale or balance or you can use objects of knowable mass. Many products have the mass written on it, or it’s an apple you can google the mass of the type of apple you have. Determine two set heights you will drop the obects from and record the height from the ground in meters. For example, you can drop the objects during your first trial from your desk, and during the second trial from just below the ceiling. TestingDrop both objects from the first set height at the same exact time and capture it in slow-motion video using the cell phone. Make sure you start recording the video before you drop the object.Drop both objects from the second set height at the same exact time and capture it in slow-motion video using the cell phone. Make sure you start recording the video before you drop the object.After Testing:Calculate the amount of time (in seconds) it took for each object to hit the ground in each set height. You can use the slow-motion capture setting and the timestamp at each frame to determine this. Record your data.Calculate the potential energy of each object at each height and record the data (PE=mgh).Answer the analysis questions listed below:Analysis QuestionsAll objects, regardless of their mass, technically fall to the ground at the same rate. Why is this?Of course not all objects hit the ground at the same time. For example, a feather and a brick are both being pulled to the ground with equal force but hit the ground at different times. What force acting on the objects causes this? How does the mass of an object effect it’s potential energy? How does height at which an object is dropped effect its potential energy?What happens to the kinetic energy of an object when you double it’s mass (hint: use the KE formula)?Bonus Questions (tough questions in which I will give you extra credit if you answer correctly)Remember energy is a closed system. Use this to calculate the velocity that each object had when falling to the ground. Some formula’s you will need:PEinitial=KEfinal.KE= ? mv2The gravitational acceleration on the moon is 1.62 m/s2. If you dropped your objects from the same set heights (a) How would that effect the time it would take for the objects to hit the ground and (b) How would that effect the potential energy the objects have at each starting height?Practice Problem Answer:A hockey puck has a mass of 0.17 kg and is positioned 15 meters above the ground. Calculate it’s Potential Energy: PE = (0.17) (9.8) (15) = 24.99 JoulesSample Data Sheet:Object 1 (What is it?):Mass (kg):Object 2 (What is it?):Mass (kg):Drop Location 1 (Where is it?):Height (m):Drop Location 2 (Where is it?):Height (m):Drop Location 1Object 1 Time to Ground (seconds):Object 2 Time to Ground (seconds):Object 1 Potential Energy Calculations:Object 2 Potential Energy Calculations:Drop Location 2Object 1 Time to Ground (seconds):Object 2 Time to Ground (seconds):Object 1 Potential Energy Calculations:Object 2 Potential Energy Calculations: ................
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