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>> $A block of mass 2kg is hanging over a sm$

Question

A block of mass $2 k g$ is hanging over a smooth and light pulley through a light string. The other end of the string is pulled by a constant force $F = 40 N$ . The kinetic energy of the particle increases $40 J$ in a given interval of time. Work done by tension is

A

$100 J$

B

$120 J$

C

$80 J$

D

$40 J$

Medium

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Updated on : 2022-09-05

Solution

Verified by Toppr

Correct option is C)

$\Rightarrow a = 10 m / s^{2}$
$40 - 20 = 2 a$
Let $u i = 0$
$v = a t = 10 t$
$s = \frac{1}{2} \times 10 v^{2} = 5 v^{2}$
$\Rightarrow \frac{1}{2} \times 2 \times (10 t^{2}) = 40$
$\Rightarrow 100 t^{2} = 40$
$\Rightarrow W_{T} = 40 \times 5 v^{2} = 200 v^{2} = 80 J$
Hence,
option $(C)$ is correct answer.

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