a car of mass 900 kg moves at 10 m/s. what is the braking force required to stop the car in a time of 5 seconds?

Answer 1

Find the required acceleration.

a = (Vf-Vi)/t

where Vf = final velocity and Vi = initial velocity

You want final velocity to be 0.

a = (0-10)/5
a = -2 m/s/s

Now to find the force:

F = ma
F = 900*-2
F = -1800N

The force required is 1800N applied opposite from the direction of motion.