Question

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^–1?

Answer 1

One watt is the power of an agent which does work at the rate of 1J s–1 

1 kilowatt = 1000 J s^–1 

Total Power = 150 × 500 = 7.5 × 10⁴ W 

Force = Power /velocity = 4 7.5 ×10⁴ /20 = 3.75 ×10³ N  

Force = 3750 N.