SATHEE: Work Energy And Power Question 284

Work Energy And Power Question 284

Question: A rubber ball is dropped from a height of 5m on a plane, where the acceleration due to gravity is not shown. On bouncing it rises 1.Sm. The ball loses its velocity on bouncing by a factor of

Options:

A) $\frac{16}{25}$

B) $\frac{2}{5}$

C) $\frac{3}{5}$

D) $\frac{9}{25}$

Show Answer

Answer:

Correct Answer: B

Solution:

[b] According to principle of conservation of energy Potential energy = kinetic energy

$\Rightarrow m g h = \frac{1}{2} m v^{2} \Rightarrow v = \sqrt{2 g h}$ If $ {h_1}

and h_2 $ are initial and final heights, then

$\Rightarrow v_{1} = \sqrt{2 g h_{1}}, v_{2} = \sqrt{2 g h_{2}}$

Loss in velocity, $Δ v = v_{1} - v_{2} = \sqrt{2 g h_{1}} - \sqrt{2 g h_{2}}$

$∴$ fractional loss in velocity $= \frac{Δ v}{v_{1}} = \frac{\sqrt{2 g h_{1}} - \sqrt{2 g h_{2}}}{\sqrt{2 g h_{1}}} = 1 - \frac{h_{2}}{h_{1}}$

$= 1 - \sqrt{\frac{1.8}{5}} = 1 - \sqrt{0.36} = 1 - 0.6 = 0.4 = \frac{2}{5}$

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Work Energy And Power Question 284

Question: A rubber ball is dropped from a height of 5m on a plane, where the acceleration due to gravity is not shown. On bouncing it rises 1.Sm. The ball loses its velocity on bouncing by a factor of

Options:

Answer:

Solution:

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