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Mechanics
Quick questions on Moments: the turning effect of a force, the principle of moments and equilibrium - OCR A-Level Maths A
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the moment of a force?Show answer
The moment of a force measures its turning effect about a point. It depends on the force and the perpendicular distance from the point to the line of the force.
What are the principle of moments?Show answer
For a rigid body in equilibrium, the total clockwise moment about any point equals the total anticlockwise moment, and (separately) the forces balance in every direction.
What are finding two reactions?Show answer
The standard technique is to take moments about one support, which eliminates its (unknown) reaction and gives the other directly, then resolve vertically for the first. Choosing the pivot wisely turns two unknowns into one.
What is q1?Show answer
A force of N acts perpendicular to a spanner m from the pivot. Find the moment. [1 mark]
What is q2?Show answer
A uniform rod of weight N and length m is pivoted at its centre. A N weight hangs m from the pivot. How far on the other side must a N weight hang to balance?
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