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Question: Answered & Verified by Expert
a string is wound around a hollow cylinder of mass $5 \mathrm{~kg}$ and radius $0.5 \mathrm{~m}$. If the string is now pulled with a horizontal force of $40 \mathrm{~N}$, and the cylinder is rolling without slipping on a horizontal surface (see figure), then the angular acceleration of the cylinder will be (Neglect the mass and thickness of the string)

PhysicsRotational MotionJEE MainJEE Main 2019 (11 Jan Shift 2)
Options:
  • A $20 \mathrm{rad} / \mathrm{s}^{2}$
  • B $16 \mathrm{rad} / \mathrm{s}^{2}$
  • C $12 \mathrm{rad} / \mathrm{s}^{2}$
  • D $10 \mathrm{rad} / \mathrm{s}^{2}$
Solution:
1230 Upvotes Verified Answer
The correct answer is: $16 \mathrm{rad} / \mathrm{s}^{2}$



From newton's second law

$40+\mathrm{f}=\mathrm{m}(\mathrm{R} \alpha)$ ...(i)

Taking torque about 0 we get

$40 \times \mathrm{R}-\mathrm{f} \times \mathrm{R}=\mathrm{I} \alpha$

$40 \times \mathrm{R}-\mathrm{f} \times \mathrm{R}=\mathrm{mR}^{2} \alpha$

$40-\mathrm{f}=\mathrm{mR} \alpha$ ...(ii)

Solving equation (i) and (ii) $\alpha=\frac{40}{\mathrm{mR}}=16 \mathrm{rad} / \mathrm{s}^{2}$

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