JEE Main · 2022 · 24 Jun 2022 · Shift 2 · Rotational Mechanics

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A fly wheel is accelerated uniformly from rest and rotates through 5 rad in the first second. The angle rotated by the fly wheel in the next second, will be :

(A)7.5 rad
(B)15 rad✓ Correct
(C)20 rad
(D)30 rad

Answer: (B)

Solution

Using the equation for uniformly accelerated rotational motion:

θ = \frac{1}{2} α t^{2}

.

For the first second:

5 = \frac{1}{2} α (1)^{2}

, so

α = 10

rad/s².

For the first two seconds:

θ_{t o t a l} = \frac{1}{2} (10) (2)^{2} = 20

rad.

Angle rotated in the second second:

θ_{2 n d} = 20 - 5 = 15

rad.

Answer: (B) 15 rad

JEE Main · 2022 · 24 Jun 2022 · Shift 2 · Single correct option

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