Work Energy And Power Question 241
Question: A running man has half the kinetic energy of that of a boy of half of his mass. The man speeds up by 1m/s so as to have same K.E. as that of the boy. The original speed of the man will be
Options:
A) $ \sqrt{2}m/s $
B) $ ( \sqrt{2}-1 )m/s $
C) $ \frac{1}{( \sqrt{2}-1 )}m/s $
D)
Show Answer
Answer:
Correct Answer: C
Solution:
[c] Let $ m=massofboy $ , $ M=massofman $
$ v=velocityofboy $ , $ V=velocityofman $
$ \frac{1}{2}MV^{2}=\frac{1}{2}[ \frac{1}{2}mv^{2} ] $ -(i)
$ \frac{1}{2}M{{( V+1 )}^{2}}=1[ \frac{1}{2}mv^{2} ] $ -(ii) $ Putting m = \frac{M}{2} and solving V= \frac{1}{\sqrt{2}-1} $
