In a time t in seconds, a heavy object will fall a distance x (in meters) = gt^2/2, where the t^2 is time squared and g is the acceleration of gravity, 9.8 m/s^2. Thus, at 1/400 second, the object will fall 0.0306 mm, hardly a simple blur to measure on film. However, at a 1/20 second, it will fall 1.225 cm, easily measured on film. I used the term "heavy" to insure that air friction will be negligible, so leaves or feathers won't work but marbles would. Timing the shot will be difficult but with two people working on it, it might succeed for long exposures. Roger -- _______________________________________ R. Eichhorn Professor of Mechanical Engineering University of Houston Fax: 713-743-4503 Tel: 713-743-4383 email: eichhorn@uh.edu
