Question

Joanne drives her car with a mass of 1000 kg at a speed of 20 m/s. Show that to bring her car to a halt in 10 s, road friction must exert a force of 2000 N on the car. 

Answer 1

The force acting on a car

$$F=ma=\frac{m\Delta v}{\Delta t}$$

$$F=\rm\frac{1000\: kg*20\: m/s}{10\: s}=2000\: N$$