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NEET 2019
Exam
NEET
Year
2019
Subject
Physics
Chapter
Rotational Motion

NEET 2019 · Physics · Rotational Motion

A disc of radius 2m and mass 100kg rolls on a horizontal floor. Its...

A disc of radius 2m2m and mass 100kg100kg rolls on a horizontal floor. Its centre of mass has speed of 20cms−1.20cm{s}^{- 1} . How much work is needed to stop it?

Options

  1. A3J3J
  2. B30kJ30kJ
  3. C2J2J
  4. D1J1J

Correct answer

A. 3J3J

Step-by-step solution

Energy of the cylinder =12mv2+12Iω2= \dfrac{1}{2}m{v}^{2} + \dfrac{1}{2}I{\omega}^{2}
=12mv2+12mr22v2r2= \dfrac{1}{2}m{v}^{2} + \dfrac{1}{2}\dfrac{m{r}^{2}}{2}\dfrac{{v}^{2}}{{r}^{2}}
=34mv2= \dfrac{3}{4}m{v}^{2}
=34×100×(20×10−2)2= \dfrac{3}{4} \times 100 \times {\left(20 \times {10}^{- 2}\right)}^{2}
=3J= 3J
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