Question

Calculate the work required to be done to stop a car of 1300kg moving at a speed of 54km/h

Answer 1

Mass of a car=1300 kg
Speed or velocity=54 km/h = 15 m/s 
Work required to be done to stop the car= Kinetic Energy = 1/2 X m X v X v
                                                                = 1/2 X 1300 X 15 X 15
                                                                = 146250 Joules

Answer 2

Speed of the car = 54km/h = 54× 5/18 m/s = 15m/s 
The kinetic energy of the car = 1/2 mv²
                                              = 1/2×1300× 15² J
                                              = 1/2×1300× 15×15 J
                                              = 146250J
the work required to be done to stop a car = 146250 J