A car weighing 1000 kg began braking and covered a distance of 50m to a complete stop.

A car weighing 1000 kg began braking and covered a distance of 50m to a complete stop. With what speed did the car move at the moment of the beginning of braking, if the total force causing its braking is equal to 4 kN?

m = 1000 kg.

g = 9.8 m / s2.

S = 50 m.

V = 0 m / s.

Fstorm = 4 kN = 4000 N.

V0 -?

2 Newton’s law for a car when braking will have the form: m * a = Fstorm.

The acceleration of the car a during braking is expressed by the formula: a = (V0 ^ 2 – V ^ 2) / 2 * S, where V0, V are the initial and final speed of the car during braking, S is the braking path.

Since at the end of braking the car stopped, then V = 0 m / s, the formula will take the form: a = V0 ^ 2/2 * S.

m * V0 ^ 2/2 * S = Ftorm.

V0 ^ 2 = Ftorm * 2 * S / m.

V0 = √ (Ftorm * 2 * S / m).

V0 = √ (4000 N * 2 * 50 m / 1000 kg) = 20 m / s.

Answer: the vehicle speed at the beginning of braking was V0 = 20 m / s.