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NEET PHYSICSMedium

A string is wrapped along the rim of a wheel of the moment of inertia 0.10 kg-m20.10 \text{ kg-m}^2 and radius 10 cm10 \text{ cm}. If the string is now pulled by a force of 10 N10 \text{ N}, then the wheel starts to rotate about its axis from rest. The angular velocity of the wheel after 2 s2 \text{ s} will be:

A

40 rad/s40 \text{ rad/s}

B

80 rad/s80 \text{ rad/s}

C

10 rad/s10 \text{ rad/s}

D

20 rad/s20 \text{ rad/s}

Step-by-Step Solution

Given: Moment of inertia, I=0.10 kg-m2I = 0.10 \text{ kg-m}^2 Radius, R=10 cm=0.1 mR = 10 \text{ cm} = 0.1 \text{ m} Force, F=10 NF = 10 \text{ N} Time, t=2 st = 2 \text{ s} Initial angular velocity, ω0=0\omega_0 = 0 (since it starts from rest)

The torque acting on the wheel is given by: τ=F×R=10×0.1=1 N m\tau = F \times R = 10 \times 0.1 = 1 \text{ N m}

Using Newton's second law for rotational motion, τ=Iα\tau = I\alpha, we can find the angular acceleration α\alpha: α=τI=10.10=10 rad/s2\alpha = \frac{\tau}{I} = \frac{1}{0.10} = 10 \text{ rad/s}^2

Now, using the first equation of rotational kinematics to find the final angular velocity ω\omega: ω=ω0+αt\omega = \omega_0 + \alpha t ω=0+10×2=20 rad/s\omega = 0 + 10 \times 2 = 20 \text{ rad/s}

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