Work Energy Power

JEE Main level, numerical answer, medium

78 of 183

Question 78 of 183

A spherical body of mass 2kg2kg starting from rest acquires a kinetic energy of 10000J10000J at the end of 5th{5}^{\text{th}} second. The force acted on the body is _____ NN.

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Answer: 40

Given kinetic energy, 12mv2=10000J\dfrac{1}{2}m{v}^{2}=10000J
⇒12×2×v2=10000\Rightarrow \dfrac{1}{2}\times 2\times {v}^{2}=10000
⇒v2=10000\Rightarrow {v}^{2}=10000
⇒v=100ms−1\Rightarrow v=100m{s}^{-1}
Also,
⇒v=at=a×5=100\Rightarrow v=at=a\times 5=100
⇒a=20ms−2\Rightarrow a=20m{s}^{-2}
Therefore, force acting
F=ma=2×20=40NF=ma=2\times 20=40N

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