Forces and Motion

Various terms used for the turning effect of forces

Physics Narrative for 11-14 Supporting Physics Teaching

Other terms for the turning effect of forces

Moments are not the only words used to quantify the action of forces that cause turning. Read more here.

Moment is the only word that we choose to use here for the turning effect of a force acting around a pivot. You may also see the words torque and couple referred to. In fact engineers regularly use calibrated torque wrenches (specially designed spanners) to tighten bolts by just the right amount. Mountain bikes might typically have bolts which need to be tightened with moments of 4 metre newton to 12 metre newton. If you try to tighten beyond the setting of the torque wrench, it starts slipping.

The term torque might be reserved for those situations where the turning effect is transmitted by a shaft. Screws, bolts and drive shafts can all be described as providing torques.

A couple is simply a pair of moments. The forces and lengths are identical in magnitude, but act in opposite directions.

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