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  • A body is dropped on ground from a height    and    after hitting the ground, it reb

A body is dropped on ground from a height  h_{1}  and    after hitting the ground, it rebounds to a height 'h_{2}'. If the
ratio of velocities of the body just before and after hitting ground is 4, then percentage loss in kinetic energy of
the body is  \frac{_{x}}{4} . The value of x is ________.

Option: 1

375


Option: 2

-


Option: 3

-


Option: 4

-


Answers (1)

best_answer

Let u and v be speeds, just before and after body strikes the ground.

Given  \frac{\mathbf{u}}{\mathbf{v}}=\frac{4}{1}

loss in KE:\DeltaKE  =\frac{\frac{1}{2} m u^2-\frac{1}{2} m v^2}{\frac{1}{2} m u^2}

\begin{aligned} & \triangle \mathrm{KE}=1-\left(\frac{\mathrm{v}}{\mathrm{u}}\right)^2=1-\frac{1}{16}=\frac{15}{16} \\ & \text { Percentage loss }=\frac{15}{16} \times 100=375 \end{aligned}

 

Posted by

Rakesh

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