Question

Question 27
Define watt. Express kilowatt in terms of joule per second. A 150 kg car engine develops 500 W for each kg. What force does it exert in moving the car at a speed of $20m{s}^{-1}$?

Answer 1

One watt is the power of an agent which does work at the rate of $1J{s}^{-1}$.
Given,

Total Power $=150\times 500=7.5\times {10}^{4}W$

We know that,
$Power=Force\times velocity$
$\Rightarrow Force=\frac{Power}{velocity}=\frac{7.5\times {10}^4}{20}=3.75\times {10}^{3}N$
$\Rightarrow Force=3750N$.