[Virginia Tech Department of Physics]

Lecture Demonstrations


M28: Falling Bodies


Purpose: To demonstrate the relation y=(1/2)gt2



The apparatus consists of a cord approximately 3.5 m long with weights tied to it at such spacings to produce constant time intervals between the sounds of the weights hitting the floor. The length of the cord is about 3.5 m and the spacings of the weights are calculated to produce a time interval of 0.15 sec.

The class should first be shown that the weights are distant from the bottom y according to the relation y = (1/2)gt2 for Dt = 0.15 sec. Thus, since t = Sum[ (Dt)i ], the following table shows the predicted y values for constant Dt:

    t (sec)   y (cm)

     0.00        0
     0.15       11
     0.30       44
     0.45       99
     0.60      176
     0.75      276

Stand on the desk and hang the cord over a pie tin. When released, the sound of the weights hitting the tin will occur at constant intervals.

Please wrap the cord back around the cardboard when done.

Equipment List: Storage Location: CHEMP 130A


Cord, Weights, Metal plate D5.3


Manual: None   Setup Notes: M28 PIRA #:
Manufacturer(s): VT Other school's Demonstration web pages



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