MCQ
The kinetic energy of a body decreases by $36\%$. The decrease in its momentum is ............... $\%$
- A$36$
- ✓$20$
- C$8$
- D$6$
✓
Answer
Correct option: B.
$20$
b
(b) $P = \sqrt {2\,mE} $ $\therefore P \propto \sqrt E $
(b) $P = \sqrt {2\,mE} $ $\therefore P \propto \sqrt E $
In given problem $K.E.$ becomes $64\%$ of the original value.
$\frac{{{P_2}}}{{{P_1}}} = \sqrt {\frac{{{E_2}}}{{{E_1}}}} = \sqrt {\frac{{64E}}{{100E}}} = 0.8$==>${P_2} = 0.8\,P$
$\therefore {P_2} = 80\% $ of the original value.
i.e. decrease in momentum is $20\%$.
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