Inelastic Collisions

On An Air Track

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How closely does the theoretical model of inelastic collisions match the results of actual inelastic collisions?


air track

2 gliders

2 photogates

computer interface

ULI Timer software

standard masses

laboratory balance

3x5 card

velcro or plasticine

Apparatus Diagram


In this lab, a "bullet" glider is given an initial velocity so that it collides inelastically with a stationary "target" glider. (There is no loss of generality in this - be sure that you understand why.) Use velcro or plasticine to make the gliders stick together after the collision. You can measure the masses of the gliders, and can use the photocells to measure the velocity of the target glider before and after the collision.

The "Collisions" experiment for the Vernier ULI Timer is set up to measure times for 2 photocells. Be sure that the 3x5 card target interrupts both photocells. Each time, T1 and T2, record the time that the target blocks the photocell, so the average velocity of the cart through the photocell is the length of the card divided by the time. If you enter the length of the card into the "Length" field in the setup window, the computer will compute the velocities for you.

You can vary the mass of the gliders by taping standard masses to them. (Balance is important!), and of course, it is easy to vary the initial velocity of the "bullet" glider.

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last update February 13, 1999 by JL Stanbrough