Lab 3.2: Momentum, Energy and Collisions

Question:
How can we demonstrate that momentum is conserved during a collision?
Learning Outcome:

• ​Observe collisions between two carts, testing for the conservation of momentum.
• Measure energy changes during different types of collisions.
  
• Classify collisions as elastic, inelastic, or completely inelastic.
  

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Your digital poster or slide show will include the following:

• Title
• Purpose / Objective
• Setup
• Data, Graphs, and/or Calculations to support your results
• Conclusion
• Error Analysis

Materials

• Apple or Android phone or tablet or Chromebook with Bluetooth
• Lab Quest 2
• Dynamics carts:
  • 2 carts with magnetic bumpers
  • 2 carts with velcro
• Dynamics carts track
• Motion Detectors (2) with appropriate cables

Procedure

1. Measure the masses of your carts. Label the carts as cart 1 and cart 2.
2. Set up the track so that it is horizontal. Test this by releasing a cart on the track from rest.
   The cart should not move.
3. Practice creating gentle collisions by placing cart 2 at rest in the middle of the track, and release cart 1 so it rolls toward the first cart, magnetic bumper toward magnetic bumper. The carts should smoothly repel one another without physically touching.
4. Place a Motion Detector at each end of the track, allowing for the 0.15 m minimum distance between detector and cart. Connect the Motion Detectors to the DIG/SONIC 1 and DIG/SONIC 2 channels of the Lab Quest 2. Set the Motion Detectors to the cart symbol.

Magnetic Bumpers

1. Press Collect to begin taking data. Repeat the collision you practiced above and use the position graphs to verify that the Motion Detectors can track each cart properly throughout the entire range of motion. You may need to adjust the position of one or both of the Motion Detectors. Press Stop once the second cart reaches the other end of the track. 
2. From the velocity graphs you can determine an average velocity before and after the collision for each cart. To measure the average velocity during a time interval, drag the cursor across the interval. Click the Statistics button to read the average value. Measure the average velocity for each cart, before and after collision, and enter the four values in the data table. Delete the statistics box. 
3. Perform one more run.
   

Velcro Bumpers

1. Change the collision by turning the carts so the Velcro bumpers face one another. The carts should stick together after collision. Practice making the new collision, again starting with cart 2 at rest. 
2. Press Collect to begin taking data and Stop once the carts reach the other end of the track. 
3. Measure and record the cart velocities in your data table. 
4. Perform one more run.
   

Velcro and Magnetic Bumpers

1. Face the Velcro bumper on one cart to the magnetic bumper on the other. The carts will not stick, but they will not smoothly bounce apart either. Practice this collision, again starting with cart 2 at rest. 
2. Press Collect to begin taking data and Stop once the carts reach the other end of the track. 
3. Measure and record the cart velocities in your data table. 
4. Perform one more run.

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