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Paper 2 · June 2024 · Direct variation

The extension yy of an elastic string varies directly as the magnitude of the force FF extending it. Given y=0.45y=0.45 m when F=6F=6 N, express FF as a function of yy.

Model answer

F=40y/3

Also accepted: 40y/3, F = 40y/3

Explanation

Direct variation gives y=kFy=kF, so 0.45=6k0.45=6k and k=340k=\dfrac{3}{40}. Then y=340Fy=\dfrac{3}{40}F, and making FF the subject, F=403yF=\dfrac{40}{3}y.

Derived from ZIMSEC Pure Mathematics Paper 2, June 2024, Q1

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