Elastic Collisions

On An Air Track

[Home][Help][Lab Index]


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


air track

2 gliders

2 photogates

computer interface

ULI Timer software

standard masses

laboratory balance

2 3x5 cards

Air Track & Apparatus Diagram


In this lab, a "bullet" glider is given an initial velocity so that it collides elastically with a stationary "target" glider. (There is no loss of generality in making the target glider stationary before the collision. Be sure that you understand why.) The metal spring bumpers on the gliders can make them collide elastically. 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 targets interrupt both photocells. Two times will be recorded by photocell T1 for each collision - the first measures the incident velocity of the bullet glider, and the second measures its final velocity. Each time, T1 and T2, record the time that the target card 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.

[Home][Help][Lab Index]
last update February 17, 1999 by JL Stanbrough