Question

A particle of mass $2\, kg$ starts moving in a straight line with an initial velocity of $2\, ms ^{-1}$ at a constant acceleration of $2\, ms ^{-2}$. Then rate of change of kinetic energy

• A. is four times the velocity at any moment
• B. is two times the displacement at any moment
• C. is four times the rate of change of velocity at any moment
• D. is constant through out

Answer 1

Answer: (A)

As, $K=\frac{1}{2} m v^{2}$
$\frac{d K}{d t}=m v \cdot \frac{d v}{d t}=\left(m \frac{d v}{d t}\right) v=\text{mav}=4 v$
$\because m=2\, kg$ and $a = ms ^{-2}$