A 1200-kg car comes to rest from a speed of 25 m/s in a distance of 75 m. If the brakes are the only thing making the car come to a stop, calculate the magnitude of the force that the brakes apply on the car.

5000 N

Explanation:

First we need to calculate the acceleration the car had.

We can do that using Torricelli formula:

V^2 = Vo^2 + 2aDS,

where V = 0, Vo = 25, DS = 75

0 = 25^2 + 2*a*75

150a = - 625

a = - 4.1667 m/s^2

The force is calculated multiplying the mass and the acceleration, so:

F = m*a = 1200 * (-4.1667) = - 5000 N

The magnitude of the break force is 5000 N (the sign only indicates the direction, the magnitude is only the value without sign)