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Torque and Moments

Understanding torque

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Why does a longer wrench help?

A wheel nut is rusted tight. A short wrench will not move it. You slide a pipe over the handle and it turns. You are pulling with the same arm strength, so what changed?

Wrench 0.150 metres long with a 100 newton force at 90.0 degrees to the handle. Moment arm 0.150 metres. Torque 15.0 newton metres, counter-clockwise.
Wrench 0.150 metres long with a 100 newton force at 90.0 degrees to the handle. Moment arm 0.150 metres. Torque 15.0 newton metres, counter-clockwise.
Short wrench: 100 N at 0.15 m
A 100 newton force perpendicular to a short 0.15 metre wrench.
Wrench 0.450 metres long with a 100 newton force at 90.0 degrees to the handle. Moment arm 0.450 metres. Torque 45.0 newton metres, counter-clockwise.
Wrench 0.450 metres long with a 100 newton force at 90.0 degrees to the handle. Moment arm 0.450 metres. Torque 45.0 newton metres, counter-clockwise.
Long wrench: 100 N at 0.45 m
The same 100 newton force perpendicular to a longer 0.45 metre wrench.

The turning effect of a force about a pivot is called torque (also called a moment). Over the next few minutes you will predict it, test it, calculate it, and use it.