Part B: How Much Force is Required?

1. Your teacher will supply you with a rubber stopper and an attached string. You should wear safety glasses to protect your eyes in case the string should break or your partner accidentally loses grip of the string. You will use the stopper and string as a qualitative way to investigate the force needed to move something in a circle.

Twirl the stopper at a slow speed in a horizontal circle. Increase the speed. Observe the force that your fingers are applying to the string as you increased the speed.

Everyone must be wearing safety glasses. Stand clear of anything that is glass.

• a) Write down a description of what you observed concerning the speed of the stopper and the force on your fingers.

• a) Compare the force that your fingers applied to a string with one rubber stopper and a string with more than one cork.
• b) In Steps 1 and 2 did you keep the speeds and radii (length of string) of the twirls identical? Why is this important?
• c) Write down your observations about the force of your fingers and the mass of the stoppers.