A car moving at a speed of 18 m / s, when braking, went to a full stop 90 m. How long did the braking last?

Distance covered by the bus when braking:

S = (V² – V0²) / 2a, where S is the distance covered by the bus (S = 90 m), V is the final speed of the vehicle (V = 0 m / s), V0 is the initial speed of the vehicle (V0 = 18 m / s) , a is the acceleration of the car (V = V0 – at (equally slow motion); 0 = V0 – at; a = V0 / t).

S = (V² – V0²) / 2a = S = (0 – V0²) / (2V0 / t) = V0 * t / 2.

Travel time:

t = 2S / V0 = 2 * 90/18 = 10 s.

Answer: Braking of the car lasted 10 seconds.