Question

the power required by engine of car of mass 1000 kg to accelerate it from the rest to a speed of 72km/h in 20s is
1)10kw.
2)1 kw
3)100kw
4)1000kw​

Answer 1

Answer: Power is 10kW. Option-1 is correct.

Explanation:

• Given that the car of mass 1000kg is to be accelerated from rest to 72km/h speed in 20s.
• The final speed is 72km/h = 20m/s.
• The energy required is given by the equation $E=\frac{1}{2} m(v^{2} -u^{2} )$ where u=0m/s.
• $E=\frac{1}{2} (1000)(20^{2} -0^{2} )\\E=200000J$
• Power is energy per unit time and time is 20s.
• $P=\frac{200000}{20} \\P=10000W\\P=10kW$
• So, first option is correct.