Question

A $500kg$ car, moving with a velocity of $36km{h}^{-1}$ 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)

$u=10m{s}^{-1},v=20m{s}^{-1}$
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
$P=\frac{500\times 30\times 10}{2\times 60}W=1250W$