Q187 / 200 · TS EAMCET 2002 · Physics
A body of mass $2 \mathrm{~kg}$ starts from rest and moves with uniform acceleration. It acquires a velocity $20 \mathrm{~ms}^{-1}$ in $4 \mathrm{~s}$. The power exerted on the body in $2 \mathrm{~s}$ in watts is
- A$50$
- Correct answerB$100$
- C$150$
- D$200$
Solution
$m=2 \mathrm{~kg}, u=0, v=20 \mathrm{~m} / \mathrm{s}, t=4 \mathrm{sec}$
Acceleration $a=\frac{v-u}{t}=\frac{20-0}{4}=5 \mathrm{~m} / \mathrm{s}^2$
$\therefore \quad$ Force applied $F=m a=2 \times 5=10 \mathrm{~N}$
Velocity at the end of $2 \mathrm{sec}$
$$
v=u+a t=0+5 \times 2=10 \mathrm{~m} / \mathrm{s}
$$
$\therefore \quad$ Power $P=F v=10 \times 10=100$ watt
Hence, the correct answer is option: 'B'.