The car was moving at a speed of 72 km h what will be the speed of the car 15 minutes after the start of braking

The car was moving at a speed of 72 km h what will be the speed of the car 15 minutes after the start of braking when braking, the acceleration is constant and equal to the modulus of 9 m with which way the car will pass during this time

Problem data: V1 (speed at which the given vehicle was moving, initial speed) = 72 km / h (in SI V1 = 20 m / s); t (time elapsed after the start of braking) = 15 min (in SI t = 900 s); a (acceleration modulus) = 9 m / s2.

1) Speed after 15 minutes: V2 = V1 – a * t = 20 – 9 * 900 = -8080 m / s <0 m / s, therefore, after 15 minutes the car will stop and V2 = 0 m / s.

2) The path of the car in 15 minutes (braking distance): S = (V2 ^ 2 – V1 ^ 2) / 2a = -V1 ^ 2 / 2a = -20 ^ 2 / (2 * (-9)) = 400/18 = 22.22 m.