Question

A motor car is moving with a velocity of 90 km per hour and it takes 4 second to stop after the brakes are applied calculate the force exerted by the break on the motor car if the mass along with the passenger is hundred kg

Answer 1

force exerted by the brake will be 625 N

Answer 2

Speed of car = 90 km/h = 25 m/s
Time taken to stop the car = 4s
Mass of car along with passenger = 100 kg

Acceleration / retardation = -25 /4 = 6.25 m/$s^{2}$

Force = mass * acceleration  = 100 kg * 6.25 m/$s^{2}$ = 625 N.