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) 15π (b) 30 (c) 10√(2) (d) 5π

Answer: (c). In 3 s the body covers 3/4 of a revolution, i.e. 270°. Start and end radii are perpendicular, so displacement = √(r² + r²) = r√2. = 10√(2) m. So the answer is (c) 10√(2).

A body is moving with constant speed, in a circle of radius 10 m. The… | JEE Main 2023 (31 Jan, Shift 2)

Q23JEE Main 2023 · 31 JAN · SHIFT 2Medium

Angular Variables

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

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Answer: (c)

In 3 s the body covers $3/4$ of a revolution, i.e. $270^\circ$ .
Start and end radii are perpendicular, so displacement $= \sqrt{r^2 + r^2} = r\sqrt2$ .
$= 10\sqrt{2}$ m.
So the answer is (c) $10\sqrt{2}$ .

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