When braking the car, its speed decreased from 45 km / h to 9 km / h within 4 seconds to determine

When braking the car, its speed decreased from 45 km / h to 9 km / h within 4 seconds to determine the acceleration of the car and the distance traveled during braking.

Task data: V1 (initial speed) = 45 km / h (in SI V1 = 12.5 m / s); V2 (final speed) = 9 km / h (in SI V2 = 2.5 m / s); t (auto deceleration time) = 4 s.

1) Auto acceleration: a = (V2 – V1) / t = (2.5 – 12.5) / 4 = -2.5 m / s2.

2) Distance when braking: S = (V2 + V1) * t / 2 = (2.5 + 12.5) * 4/2 = 30 m.

Answer: The acceleration of the car was equal to -2.5 m / s2; the distance covered is 30 m.