Question

The velocity of a car increase from 54km per hour to 72 km per hour. How much is the work done if the mass of the car is 1500kg?

Answer 1

Mass of car m = 1500 kg

Initial velocity = 54 km/h = 54 x 5/18 = 15 m/s

Final velocity = 72 km/h = 72 x 5/18 = 20 m/s 

(1 km/h = 1000 m/ (3600 s) = 5/18 m/s

Initial kinetic energy = ½ mv2

                              = ½ x 1500 x (15)2

                              = 168750 J

Increased kinetic energy = 1/2 mv2

                           = ½ x 1500 x (20)2

                           = 300000 J

Work done = Change in kinetic energy

                = 300000 - 168750

                = 131250 J

Hence the work done by the force on the car = 131250J