JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Kinematics

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A body is moving with constant speed, in a circle of radius 10 m. The body completes one revolution in 4 s. At the end of 3rd second, the displacement of body (in m) from its starting point is:

(A)30
(B) $15 π$
(C) $5 π$
(D) $102$ ✓ Correct

Answer: (D)

Solution

One full circle takes

4 s

, so in

3 s

the body sweeps three quarters of it, an angle of

27 0^{\circ}

about the centre. The straight-line gap between start and finish is the chord subtending this angle,

d = 2 r sin \frac{θ}{2} = 2 (10) sin 13 5^{\circ} = 2 (10) \frac{1}{2}

. The displacement from the starting point is therefore

102 m

JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Single correct option

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