Question

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

• A. $750\text{W}$
• B. $1050\text{W}$
• C. $1150\text{W}$
• D. $1250\text{W}$

Answer 1

The correct option is D $1250\text{W}$

Given,$u=36{\text{kmh}}^{-1}=36\times \frac{5}{18}=10{\text{ms}}^{-1}$ Final velocity $v=2u=20{\text{ms}}^{-1}$
From work-energy theorem,
Work done = Change in kinetic energy
From the data given in the question,
$W=\frac{1}{2}\times 500\times [{20}^2-{10}^2]=\frac{500\times 300}{2}\text{J}$
Now, the power delivered in one minute is
$P=\frac{W}{t}=\frac{500\times 300}{2\times 60}=1250\text{W}$
Thus, option (d) is the correct answer.