A driver of a moving car at 20m/s finds a child on the road 50m ahead and stops the car 10m earlier to the child. If the mass of the car with driver is 1000kg, calculate the force exerted by the brakes of the car??

Answer 1

speed:
20-at=0
t = 20/a

distance:
20(20/a) - a/2 (20/a)^2 = 50-10
a = -5 m/s^2

F = ma = ...

Answer 2

5000kg