Ball on a String

PIRA: 1D50.10

Overview:

The velocity of an object that is spinning can be counter-intuitive. In order to demonstrate what happens, we will spin a ball around and cut the rope to see which direction it goes. This allows us to see where the velocity of the spinning object is directed at the moment when the string is cut.

Materials:

Large styrofoam ball, stick with a razor blade at the end (Safety Stick), thin string (string in picture can be found in the F4 bin in room 131), volunteer/demo assistant.

Setup:

Cut a piece of string around 4 feet long, then tie one end of the string onto the loop that is attached to the styrofoam ball. Extend the razor blade only when the demo is being performed.

How To:

One person will swing the ball above their head, while another person will be below the twirling ball with the razor. Slowly move the stick with the razor up until the razor cuts the string. You may have another person in the direction of the ball’s path to catch it once the string has been cut.

Safety:

The razor is sharp! Keep the blade sheathed until it is time to cut the string. Also keep in mind which direction the blade is facing.