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} $ .
