Question

A $500\, kg$ car, moving with a velocity of $36\, km\, h ^{-1}$ on a straight road undirectionally, doubles its velocity in one minute. The power delivered by the engine for doubling the velocity is

• A. 750 W
• B. 1050 W
• C. 1150 W
• D. 1250 W

Answer 1

Answer: (D)

$u=10\, m s ^{-1}, v=20\, m s ^{-1}$
According to work-energy theorem
Work done $=$ change in kinetic energy
$=\frac{1}{2} m v^{2}-\frac{1}{2} m u^{2}$
$=\frac{1}{2} \times 500\left[20^{2}-10^{2}\right]$
$=\frac{500 \times 30 \times 10}{2}$
The power delivered by the engine is
$P=\frac{500 \times 30 \times 10}{2 \times 60} W =1250\, W$