Demo Detail

Conservation of momentum (with gliders on air track)

Purpose:
To show that during a collision between two objects momentum is conserved.

Equipment:
Air track Air pump Air hose Two gliders Weights Scale

Equipment Location:
Other

Procedure:
To start make sure the air track is level. Now put two equally weighted gliders on the air track. Make sure that at least one of them has the rubber band attachment so that they will bounce off of each other. Place one glider near the center of the track and make sure that it has not initial velocity. Then push the other cart towards the stationary one. Observe the collision. After the initial demonstration you should repeat this experiment with one car being twice the mass of the other. You should do the demonstration with the heavier car being both the one to start at rest and to start with an initial velocity.

Hints:
The easiest way to level the air track is to use the adjustable legs on the one side of the air track. Also in case a scale is not available the gliders are approximately 180 grams each.

Relevant derivations/explanations:
After the initial collision where the masses were the same the glider that started in motion should be at rest and the glider that started at rest should have the initial velocity of the other glider. When the glider that starts in motion has twice the mass of the one that started at rest there is some difference. The final velocity of the glider that started in motion should be 1/3 of it's initial velocity. The velocity of the glider that started at rest should be 4/3 that of the initial velocity of the other glider. When the glider that starts at rest is the one with twice the mass of the other it is again different. The glider that started in motion should have a final velocity of 1/3 its initial velocity. The glider that started at rest should have a final velocity of 2/3 the other gliders initial velocity.

Physics

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