Work Energy And Power Question 245

Question: When a body is projected vertically up from the ground with certain velocity, its potential energy and kinetic energy at a point A are in the ratio 2 : 3. If the same body is projected with double the previous velocity, then at the same point A the ratio of its potential energy to kinetic energy is

Options:

A) 9 : 1

B) 2 : 9

C) 1 : 9

D) 9 : 2

Show Answer

Answer:

Correct Answer: C

Solution:

[c] Let E be the total energy then

$ \frac{P.E}{K.E}=\frac{mgh}{E-mgh}=\frac{2}{3}\Rightarrow E=\frac{5}{2}mgh $

When velocity is double then inital energy becomes 4E.

So, $ \frac{mgh}{4E-mgh}=NL=\frac{mgh}{10mgh-mgh} $

On solving we get $ \frac{P.E}{K.E}=\frac{1}{9} $ .



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