A car of mass 120 kg is moving at a speed 18 km/h and it accelerates to attain a speed of 54 km/h in 5 seconds. Calculate:

(a) Given,

Initial velocity (v_i) = 18 km/h

Converting km/h to m/s

18 x $\frac{5}{18}$ = 5 m/s

Final velocity (v_f) = 54 km/h

Converting km/h to m/s

54 x $\frac{5}{18}$ = 15 m/s

Work done = Change in kinetic energy = $\frac{1}{2}$m(v_f² - v_i²)

= $\frac{1}{2}$ x 120 x (15² - 5²)

= $\frac{1}{2}$ x 120 x (225 - 25)

= 60 x 200 = 12000 J

Hence, work done = 12000J

(b) Power = $\frac{\text{work done}}{\text{time}}$ = $\frac{12000}{5}$ = 2400 watt.

Hence, power of engine = 2400 watt.