Candidates should be able to:
- understand and use the result that the effect of gravity on a rigid body is equivalent to a single force acting at the centre of mass of the body, and identify the centre of mass by considerations of symmetry in suitable cases;
- calculate the moment of a force about a point in 2 dimensional situations only (understanding of the vector nature of moments is not required);
- recall that if a rigid body is in equilibrium under the action of coplanar forces then the vector sum of the forces is zero and the sum of the moments of the forces about any point is zero, and the converse of this;
- use Newton’s third law in situations involving the contact of rigid bodies in equilibrium;
- solve problems involving the equilibrium of rigid bodies under the action of coplanar forces (problems set will not involve complicated trigonometry).
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