JAMB Physics 2019 Paper

Concept:In simple harmonic motion, speed depends on amplitude, angular speed, and distance from the equilibrium position.Explanation:The body moves between two points $20$ m apart.So the amplitude is half of that distance:$$A = \frac{20}{2} = 10 \text{ m}$$The angular speed is $\omega = 5$ rad/s.The distance from the centre is $x = 6$ m.Speed is given by:$$V = \omega \sqrt{A^2 - x^2}$$Substitute the values:$$V = 5 \sqrt{10^2 - 6^2}$$$$V = 5 \sqrt{100 - 36}$$$$V = 5 \sqrt{64}$$$$V = 5 \times 8 = 40 \text{ m/s}$$Answer:The speed is $40 \text{ m/s}$, so the correct option is C.