Conservation of momentum in an inelastic collision

This experiment uses an AirTrack with two gliders to demonstrate the conservation of momentum in an inelastic collision.  One glider is given an impulse and then passes through a photo-gate timer so that its speed can be calculated.  It then collides with a second glider and the two gliders then travel on and pass through a second photogate timer so that their common speed can be measured.  In this way the total momentum before and after the collision can be calculated and compared.