M-K3: Free Fall Independent of Initial Horizontal Velocity
 
PIRA: 1D60.20 

Equipment: Spring gun with two drilled copper balls, stand rod and table mounting bracket, level. The gun and ball are located in Set 8 Cabinet 3 Shelf 2

Setup: Mount the apparatus on a corner of the lecture table by means of a vertical stand rod. See that the rear ball which is to be dropped has a clear fall space to the floor and that the aim for the driven ball is at sufficient angle with the front of the table that the horizontally projected ball will clear the front edge of the table and fall to the floor in the open space between the table and the feet of the students on the front row. It is important that the ejection rod move horizontally. Use the level to get the setting correct. The tilt of the vertical stand rod can be controlled by adding cards or sheets of paper under one side of the foot of the bracket holding the stand rod to the table top.

There are two sets of equipment for this demonstration. The smaller outfit is a little better designed, but the larger one is more easily seen by the students.
 
 

Demonstration:

Pull the trigger to release the two balls. They will appear to strike the floor simultaneously: students will hear a single impact. This is not a very sensitive test of the fact that free fall does not depend on initial horizontal velocity; a more sensitive test is demonstration M-K4 in which a falling target is struck.