# Warm-Up Exercise for lecture 14

## Due 8:00 am, Thurs, 15 Oct 2009

Physics 105, Fall 2009

In order to apply the most torque to a screw, you should:
☑ use a wrench with a long handle
☐ use a wrench with a short handle
☐ there would be no difference

Two people sit on a seesaw. They sit in positions such that the seesaw is balanced in a horizontal position. True/False: The two people must weigh the same amount.
☐ true
☑ false

If an object is in equilibrium:
☐ the net force on it must be zero
☐ the net torque on it must be zero
☑ both of the above
☐ neither of the above

Ralph noticed that both torque and work are obtained by multiplying a force times a distance. He wants to know: how are they different? Do they have the same units? What can you tell Ralph to help him out?
Work is done on an object over a period of time--and over a certain distance having a parallel component--whereas torque is basically a force applied to the object at an instant of time, with the force applied away from the pivot at a given distance (having a perpendicular component). They do have the same units, but represent very different things. Therefore the units of torque are usually written as Nm, whereas the units of energy & work are usually written as J.