Three particles A, B and C move along the same straight line

PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

Three particles A, B and C move along the same straight line. Their masses are 1 kg1\,\text{kg}, 2 kg2\,\text{kg} and 3 kg3\,\text{kg} respectively. At a particular instant, constant forces of 3 N3\,\text{N}, 3 N3\,\text{N} and 6 N6\,\text{N} act on A, B and C in the positive direction of the line. (i) Derive an expression for the acceleration of each particle in terms of the given data without substituting numerical values. (ii) Using your expressions, rank the three accelerations from greatest to least, showing your reasoning. (iii) Suppose both the force and the mass of particle C are simultaneously doubled. Prove that its acceleration remains unchanged, and explain the underlying principle.

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