question_answer 60)

  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 speed of 20 ms-1?

Answer:

  (i) One watt is the power of a body which does work at the rate of 1 J/s. (ii) 1 kilowatt =1000 watt = 1000 J/s (iii) Given, m =150 kg,        P = 500 W and v = 20 A car engine 150 kg develops 500 watt for each kg. So, total power = 150 x 500 = 75000 W We have,           Power = Force x speed                            75000 = Force x 20                                 Force,