# Momentum, Energy and Collisions

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Momentum, Energy and Collisions Date: Oct. 30 Purpose: to identify that the momentum before and after the collision are the same, so the total momentum of the system is conserved. Theory: The collision of two carts on a track can be described in terms of momentum conservation and, in some cases, energy conservation. If there is no net external force experienced by the system of two carts, then we expect the total momentum of the system to be conserved. This is true regardless of the force acting between the carts. In contrast, energy is only conserved when certain types of forces are exerted between the carts. Hypothesis: the momentum before and after the collision should be the same. Procedure: 1: Measure the masses of the cars. 2: St up the track and balance it. 3. Practice release cart 1 gently towards the cart 2 which is in middle of the track. 4. Place a Motion Detector at each end of the track, allowing for the 0.4 m minimum distance between detector and cart. Connect the Motion Detectors to the DIG/SONIC 1 and DIG/SONIC 2 channels of the interface. 5. Click 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. 6. Place the two carts at rest in the middle of the track, with their Velcro bumpers toward one another and in contact. Keep your hands clear of the carts and click . Select both sensors and click . This procedure will establish the same coordinate system for both Motion Detectors. Verify that the zeroing was successful by clicking and allowing the still-linked carts to roll slowly across the track. The graphs for each Motion Detector should be nearly the same. If not, repeat the zeroing process. Part I: Magnetic Bumpers 7. Reposition the carts so the magnetic bumpers are facing one another. Click