Question

A 1500 kg car travelling at 75.0km/h to a screeching halt in a time of 3.00seconds. Calculate the force of friction experienced by the car.

Answer 1

According to Newton's second law:

$$ma=f,\\\space\\ m·\frac{v}{t}=f,\\\space\\ f=1500·\frac{75·1000/3600}{3}=10420\text{ N}.$$