Torque is defined as
- A. force divided by distance
- B. the scalar product of force and distance
- C. the product of force and the perpendicular distance from the axis to the line of action
- D. force multiplied by time
Explanation
Only the perpendicular distance, the moment arm, counts, which is why pushing a door near its hinge is so ineffective. Written as a vector product, torque is r cross F, with magnitude rF sin theta, so a force directed straight at the axis produces no turning effect at all. Its unit is the newton metre, which is not called a joule even though the dimensions match.