Collisions in One Dimension
1. In your own words, describe the situation to be studied in thisexperiment.
2. List and define all the parameters which will be measured directly.
3. List any quantities that will be calculated.
4. List any graphs that will be created during the analysis of thisexperiment.
1. Be very careful with the air carts. If they are dropped or mishandled,they can lose thier very smooth and very flat lower surfaces which allow themto move with very little friction.
2. Make sure that your air track is level before you start taking data. Wedon't want the carts to accelerate at all between the collision and thephotogates. If the track is not level, the parallel component of the gravitational force will cause the carts to accelerate as they did in theKinematics in One Dimension experiment.
3. Adjust the height of the photogates so that the cart's flag blocks thegate as it passes through. Make sure that it is the flag that blocks the gate,not the cart itself.
4. Adjust the distance between the photogates so that the collision can takeplace without either of the gates being blocked.
5. Collision I.
- Stationary target cart with moving incident cart, masses equal.
- Be careful when reading the times from the computer. There will betwo columns of numbers on the screen, one showing the times measured by theleft photogate and the other showing the times measured by the right photogate. Some students in the past have mistakenly thought that one column was for theincident cart only and the other column was for the target cart only.
- When recording the times for this collision, the initial time forthe target cart is essentially infinite, because the target cart was not movingbefore the collision. Put an X through all of the boxes for the initial timefor the target cart. Also for Collision I, if the two red carts have equalmasses, the first cart should come to a stop after the collision. If this isthe case, the final time for the incident cart will also be essentiallyinfinite if it is not moving after the collision. You could then also put anX through all of the final times for the incident cart. If the masses aredifferent, the incident cart will be moving after the collision and youshould record the time it takes to pass through the photogate.
- Perform three collisions with these initial conditions. Try tosend the incident cart toward the target cart with three different velocities. Don't go too fast, though, because the any rocking of the air cart willincrease the friction between it and the track.
- Calculate the total initial and total final momenta for each of thethree individual collisions. Remember that all momentum vectors toward theright end of the air track are positive and all momentum vectors toward theleft end of the air track are negative.
6. Collision II
- Stationary target cart with moving incident cart, target mass greater.
- Again, be careful when recording the times for this collision. Theinitial time for the target cart is again essentially infinite since it was notmoving before the collision.
- Again, make three trials for different incident speeds.
- Calculate the total initial and total final momenta for each ofthe three individual collisions. Remember that all momentum vectors toward theright end of the air track are positive and all momentum vectors toward theleft end of the air track are negative.
7. Collision III
- Stationary target cart with moving incident cart, incident massgreater.
- This situation is very similar to that of Collision III, exceptthat we have reversed the roles of the red and gold carts. Be careful whenrecording the times for this collision as well.
- Again, make three trials for different incident speeds.
- Calculate the total initial and total final momenta for each of thethree individual collisions. Remember that all momentum vectors pointingtoward the right end of the air track are positive and all momentum vectorstoward the left end of the air track are negative.
8. Collision IV
Head on collision, both carts initially in motion. - This type of collision is more tricky than the others in that ittakes some coordination to get the collision to take place between the twophotogates. Take a few moments to practice this before you start taking data.Be careful when recording the times for this collision. You will have two numbers in each of the two time collumns this time. Make sure you understandwhich time corresponds to which part of the motion.
- Again, make three trials for this type of experiment. Try at leastone collision with a gold target cart and one with a red target cart. Vary theinitial speeds as well.
- Calculate the total initial and total final momenta for each of theindividual collisions. Rememger that all mometum velctors pointing toward theright end of the air track are positive and all momenum vectors pointing towardthe left end of the track are negative.
9. Plot the final momentum versus the initial momentum for each of thecollisions you studied. Put all twelve data points on the same graph usingeither different shapes or different colors to distinguish between thedifferent types of collisions.
10. Calculate the initial and final Kinetic Energies for each of thesecollisions. Determine whether or not KE is conserved.
1. Your results section should have some statement describing therelationship between initial and final momenta for each of the types ofcollisions you studied. You should also state whether or not KE was conservedin each of these types of collisions.
2. Describe the motion of the carts for each of the types of collisions.Were there any general relationships between the speed of the carts before thecollisions and their speeds after the collisions? Could you predict thedirections of the carts after the collisions?
3. Describe your graph. What were the shapes of the lines for theindividual type of collisions? Were they linear or not? Was there any overalltrend? What does the shape of the graph tell you about the conservation ofmometum in collisions on the air track? Did you obtain the relationship youexpected? If not, try to determine why there was a difference between yourexpectations and your results.
4. Was Kinetic Energy conserved in any of your collisions? Is this what youexpected for this type of collision? If not, try to determine why there was adifference between your expectations and your results.
| Section | Points |
|---|
| Purpose | 1 |
| Results | 3 |
| Calculations | 3 |
| Graphs | 3 |
| Analysis | 10 |
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