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 20 m//s ?

Explanation

(i) One watt is the power of a body which does work at the rate of 1 J//s.
`1"watt"=1("joule")/("second")`
(ii) 1 kilowatt = 1000 watt = 1000J//s
(iii) Given, m=150kg, `p=500Wandv=20ms^(-1)`
A car engine 150 kg develops 500 watt for each kg. So, total power `=150xx500=75000W`
We have, `"Power"="Force"xx"speed"`
`"Force,"F=(75000)/(20)=3750N`