Table of Mechanics Demonstration List of Mechanics Equipment & Supplies Lecture Demonstrations

# Air Track Totally Inelastic Collision, 1N30.32

Topic and Concept:

Location:

• Floor Item: ME, South Wall

Abstract:

A moving glider collides with a stationary one and sticks.

 Equipment Location ID Number 2.25 m Air Track Floor Item: ME, South Wall Small & Large Air Track Gliders ME, Bay A4, Shelf #4 Red Clay Double Steel Door Bin Cabinet Air Hose Floor Item: ME, South Wall Red & White Gas Carts ME, Bay B1, Shelf #2

Important Setup Notes:

• This demonstration requires a supply of compressed air, permanent supplies located in rooms 2103, 2223, 2241.

Setup and Procedure:

1. Place air track on lecture bench, and connect the compressed air supply from the lower white panel of the Red & White Gas Cart to the track using an air hose.

2. Make sure that the gliders to be used have clay on one side and that the clay juts out a little off center (see photo).
3. Place two gliders on the track, one on an end of the track and the other roughly in the middle.
4. Turn on the air supply by opening the valve located on the lower white panel of the cart.
5. If the gliders seem to slide in one direction, this is most likely due to the track being unlevel. Adjust the set screws until this no longer occurs. It is a good idea to do this ahead of time.
6. Give the glider on the end a good push toward the glider at rest to create a collision.

Cautions, Warnings, or Safety Concerns:

• Make sure you are using compressed air (white panel) and NOT methane gas (red panel) which is extremely flammable!

Discussion:

In conservative systems, momentum is always conserved. In the lab frame, one glider is in motion and one is at rest. Thus, the total momentum of the system is P0 = m1 * v1 where m1 is the mass of the glider in motion and v1 is its speed. In an inelastic collision, the two bodies stick to each other. Since P0 = Pf , ignoring friction and air resistance, the speed of the two cars together is lower than the initial speed of the first glider. Pf = (m1 + m2) * v1+2.

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