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Rotational Motion question

2021 · 20 Jul · Shift 2 · Q72
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  5. /2021 · 20 Jul · Shift 2 · Q72

Rotational Motion question

2021 · 20 Jul · Shift 2 · Q72

JEE MainPhysicsRotational MotionNumerical+4 / −1
A body rotating with an angular speed of 600 rpm is uniformly accelerated to 1800 rpm in 10 sec. The number of rotations made in the process is ‾\underline{\hspace{2cm}}​.
Numerical answer
View written solutionFree

Correct answer: 200

  1. Given data

    • Initial angular speed: 600 rpm600\ \text{rpm}600 rpm
    • Final angular speed: 1800 rpm1800\ \text{rpm}1800 rpm
    • Time taken: 10 s10\ \text{s}10 s
  2. Convert angular speeds to rotations per second 600 rpm=60060=10 rps600\ \text{rpm} = \frac{600}{60} = 10\ \text{rps}600 rpm=60600​=10 rps 1800 rpm=180060=30 rps1800\ \text{rpm} = \frac{1800}{60} = 30\ \text{rps}1800 rpm=601800​=30 rps

  3. Use average angular speed for uniform acceleration Since the angular acceleration is uniform, the average angular speed is ωavg=ωi+ωf2=10+302=20 rps\omega_{\text{avg}} = \frac{\omega_i + \omega_f}{2} = \frac{10 + 30}{2} = 20\ \text{rps}ωavg​=2ωi​+ωf​​=210+30​=20 rps

  4. Find total number of rotations N=ωavg×t=20×10=200N = \omega_{\text{avg}} \times t = 20 \times 10 = 200N=ωavg​×t=20×10=200

  5. Final answer The number of rotations made is 200\boxed{200}200​

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