A car, mass of 1225 kg, traveling at 105 km/h, slows to a stop in 53 m. What is the size and direction of the force that acted on the car?

Answer 1

First, the speed has to be converted to m/s units (SI)

105 km/h x 1000m/3600s ≅ 29 m/s

Then, we have to find the acceleration from kinematics to reach the force.

V_(final)² = V_(initial)² + 2 a x ==> 0 = 29² - 2 * a * 53 ==> a ≅ 7.9 m/s²

F = ma ==> F = 1225 x 7.9 = 9677 N ≅ 9700 N