PHY 202/PHY 241 Conservation of momentum: Elastic collisions Name: ________________________________ Purpose: Familiarize the student with the concept of conservation of momentum. Procedure Part 1 –...

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PHY 202/PHY 241 Conservation of momentum: Elastic collisions Name: ________________________________ Purpose: Familiarize the student with the concept of conservation of momentum. Procedure Part 1 – One-dimensional motion 1. Go to PHET Collision Lab (https://phet.colorado.edu/en/simulation/legacy/collision-lab) simulation. You should be able to click on the arrow in the middle of the display to run it, or, if you want, you can download it onto your computer. This simulation requires Flash to be installed on your computer. 2. Initially, you will see two balls, along with some display options. Uncheck all of these and make sure that “Elasticity” is set for 100% 3. Click on “More Data” to see the initial conditions of the simulation. Record these in Table 1. 4. Before running simulation, predict what the momentum of each object will be after the collision and record in Table 1. 5. Run the simulation and record the momenta of each object in Table 1. 6. Using the momenta values and masses before and after the collision, calculate the total energy of each object before and after the collision. Record in Table 1. 7. Run two more trials, adjusting the masses to a) equal to each other, and b) be reversed from the first trial, and repeat the steps above to finish out Table 1. You will need to click on the “Reset All” button to set up for each trial. Part 2 – Two-dimensional motion 1. Click on the “Advanced” tab. You should now see two spheres. Uncheck the “Velocity Vectors” button and click on the “More Data” button. 2. Position Ball 1 at x = 0.5 and y = 0 by inserting these values in the white boxes for those positions. Position Ball 2 at x = 1.5 and y = 0.2 (this will produce a somewhat glancing collision). Set the initial velocity of Ball 1 to have an x-component of 1 and y-component of zero. Set the x- and y-components of Ball 2 at zero. Record initial conditions in Table 2 as listed. 3. Run the simulation and record the final momenta in Table 2. 4. Using the momenta values and masses before and after the collision, calculate the total energy of each object before and after the collision. Record in Table 2. 5. Run two more trials, adjusting the masses to a) equal each other, and b) be reversed from the first trial, and repeat the steps above to finish out Table 2. Table 1 Mass 1 (kg) Predicted Momentum (kg m/s) Momentum (kg m/s) Kinetic Energy (J) Mass 2 (kg) Predicted Momentum (kg m/s) Momentum (kg m/s) Kinetic Energy (J) Trial 1 before 0.5 X 1.5 X Trial 1 after 0.5 1.5 Trial 2 before 1 X 1 X Trial 2 after 1 1 Trial 3 before 1.5 X 0.5 X Trial 3 after 1.5 0.5 Table 2 Mass 1 (kg) x-Momentum (kg m/s) y-Momentum (kg m/s) Kinetic Energy (J) Mass 2 (kg) x-Momentum (kg m/s) y-Momentum (kg m/s) Kinetic Energy (J) Trial 1 before 0.5 1.5 Trial 1 after 0.5 1.5 Trial 2 before 1 1 Trial 2 after 1 1 Trial 3 before 1.5 0.5 Trial 3 after 1.5 0.5 Analysis 1. If there was a difference between your predicted final momentum for each object and that determined by the simulation, calculate a percent error, using the simulation value as the accepted. 2. Calculate the total momentum of the system after the collision, based on the data in Table 1. 3. Calculate the total energy of the system after the collision, based on the data in Table 1. 4. Calculate the total momentum of the system after the collision, based on the data in Table 2. 5. Calculate the total energy of the system after the collision, based on the data of Table 2. Questions 1. Comparing your initial and final momenta from data in Table 1, was momentum conserved? Explain why or why not. 2. Comparing your initial and final kinetic energies from data in Table 1, was kinetic energy conserved? Explain why or why not. 3. Comparing your initial and final momenta from data in Table 2, was momentum conserved? Explain why or why not. 4. Comparing your initial and final kinetic energies from data in Table 2, was kinetic energy conserved? Explain why or why not.