Question

To avoid an accident, a driver steps on the brakes to stop a 1000-kg car traveling at 65km/h. if the braking distance is 35 m, how much force is necessary to stop the car?

Answer 1

First, find the needed acceleration needed for the car to stop from its initial velocity given the distance. This is calculated through the equation,
                                             2ad = Vf² - Vi²
where a and d are acceleration and distance, respectively. Vf and Vi are final and initial velocities, respectively. Substituting the known values,
           2(a)(35 m) = (0 m/s)² - ((65 km/h) x (1000 m/ 1 km) x (1 hr / 3600 s))²
The value of acceleration is -4.66 m/s².
The force needed to stop the car is the product of the mass and the acceleration. The operations gives us an answer of -4,660 N. We take the positive value, 4,660 N.