Question

Calculate the work requured to be done to stop a car of 1500kg moving at a velocity of 69km/h?

Answer 1

Explanation:

Mass of the car m = 1500 kg 

Velocity of the car v = 60 km/h 

= 60×1000 /60×60 = 50 /3 m/s

The car is in motion, so its energy = kinetic energy = 1 /2 mv2

= 1 /2 (1500) ( 50/ 3 ) 2 J 

= 1/ 2 × (1500) × 2500/ 9 J 

= 208333.3 J

The kinetic energy of the car, when it comes to rest = 0 J 

Work done on object = change in kinetic energy 

                                  = 208333.3 − 0 J 

                                  = 208333.3 J 

Hence, the work required to stop the car is 208333.3 J