Question

a 1000.kg car moving at north at 100. km/hr brakes to a stop in 50. m within a uniform acceleration. what are magnitude and direction of the net force on the car ?

Answer 1

$$F=ma$$

$$a=\frac{v^2}{2s}$$

$$F=m\frac{v^2}{2s}=1000\frac{(\frac{100}{3.6})^2}{2(50)}=7716\ N$$

Direction: at south.