# Proving force

1. Oct 5, 2004

### UrbanXrisis

Two physics students are having a debate about the best way to define a force scale using rubber bands. Each one is trying to convince you to do it their way. They have the following apparatus to use in tests:

A bunch of identical small rubber bands
10N spring scale
meter stick

Joe argues that: “It’s so much easier to use one rubber band to define a force scale than many. All I have to do is to stretch the rubber band by 1 cm to get one unit of force, then by 2 cn to get two units of force, and then by 3 cm to get three units of force and so on.”

Larry counters: “We do not know whether or not rubber band are linear. Maybe the force the rubber band exerts at 3 cm is not really three times tan the force it exerts at 1 cm. I think it is absolutely necessary to use many identical looking rubber bands in parallel with each other to define a force.”

How could I design a test using the same apparatus Joe and Larry have to prove who is right?

2. Oct 5, 2004

### kuenmao

Sounds like homework to me O_O...wrong section.

A hint is to look up Hookes law.

3. Oct 5, 2004

### UrbanXrisis

in the equation F=kx...why doesn't mass come into play?

4. Oct 6, 2004

### HallsofIvy

Staff Emeritus
Why should it? The force is due completely to the rubber band. The rubber band doesn't care if it is pulling a 1 gram mass or a 10000 kg mass- it exerts the same force.

Of course, when you are calculating the acceleration due to that force, THEN mass comes into play.