Part 04 · Rotation and gravity · Card 4 of 11
Torque
The turning effect of a force, torque = r F sin theta. Longer lever arms need less force.
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Analogy
A long spanner loosens a stuck nut more easily.
Example
Wrench
tau = r F sin 90tau = 0.3 x 100 x 1tau = 30 N m
In practice
A 100 N push at the end of a 0.3 m wrench gives 30 N m.
Practice
Flashcards
- What is the unit of torque?Newton metre (N m).
Questions people ask
Why is a door handle far from the hinge?
Torque equals force times distance from the pivot. Placing the handle far from the hinge gives a long lever arm, so a small push produces a large turning effect. Pushing close to the hinge takes much more force to open the door.
Is torque a vector?
Yes. Its direction comes from the right-hand rule: curl your fingers the way the force turns the object, and your thumb points along the torque. At first-year level, you often treat torque as positive for anticlockwise turns and negative for clockwise ones.