Book: # 1

     In this short Film, we examine the motion of an air track glider under various conditions of acceleration. The passage of the glider in front of markers of known arrangement is detected by photocells on the markers and recorded in the lower part of the frame. This provides two related measurements of time. The "transit time" or interval required for a glider to pass in front of a given marker, is indicated by the width of a recorded peak. this is produced by a narrow slit, cut in the glider at its center point. 
Two general cases are shown:

-CONSTANT VELOCITY: The air track is adjusted so that a glider will move with constant velocity.
-UNIFORM ACCELERATION: The air track is adjusted so that the glider accelerates uniformly from left to right. 

     Next, markers are placed at positions 0, D, 4D and 9D so that successive marker separations are D, 3D and 5D. At the same time, the car is fitted with three colored masks having width of 1/2 D, D and 3/2 D. Each of these masks is made to pass across a photocell on a marker of the same color (red mask, red marker, etc.) A fourth photocell is uncovered as the glider starts to move, and provides an initial time reference.