By the end of this section, you will be able to:
- Describe how the magnitude of a torque depends on the magnitude of the lever arm and the angle the force vector makes with the lever arm
- Determine the sign (positive or negative) of a torque using the right-hand rule
- Calculate individual torques about a common axis and sum them to find the net torque
Consider how you would answer these questions. Then bring this to class for a group discussion.
Shown below are six situations where a student is holding a meter stick at the left end at various angles. A 1-kg mass is hung on the meter stick at different locations. All of the meter sticks are identical. Rank these situations, from hardest to easiest, on the basis of how difficult it would be for the student to hold the meter stick from the left end in the position shown.
A plumber pushes straight down on the end of a long wrench as shown. What is the magnitude of the torque he applies about the pipe at lower right?
|(a) (0.80 m)(900 N)sin 19°|
|(b) (0.80 m)(900 N)cos 19°|
|(c) (0.80 m)(900 N)tan 19°|
|(d) (0.80 m)(900 N)/(sin 19°)|
|(e) none of the above|