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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Rotational Mechanics

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Rotational Mechanics

A block is suspended from a string wrapped on a disc of radius 20...

A block is suspended from a string wrapped on a disc of radius 20 cm20 \text{ cm}, which is free to rotate about its fixed horizontal axis. If the angular speed of the disc is 10 rad/s10 \text{ rad/s} at a particular instant, at what speed is the block descending at that instant?

Options

  1. A2 m/s2 \text{ m/s}
  2. B0.5 m/s0.5 \text{ m/s}
  3. C20 m/s20 \text{ m/s}
  4. D200 m/s200 \text{ m/s}

Correct answer

A. 2 m/s2 \text{ m/s}

Step-by-step solution

Given, radius of the disc, R=20 cm=0.2 mR = 20 \text{ cm} = 0.2 \text{ m}

Angular speed of the disc, ω=10 rad/s\omega = 10 \text{ rad/s}

The speed of the descending block is equal to the tangential speed of the points on the rim of the disc.

v=Rωv = R \omega

v=0.2×10=2 m/sv = 0.2 \times 10 = 2 \text{ m/s}
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