How long after the start of braking will the bus stop, traveling at a speed of 12 m / s

How long after the start of braking will the bus stop, traveling at a speed of 12 m / s, if the coefficient of friction is 0.4?

Initial data: V0 (speed at which the bus was moving) = 12 m / s; μ (coefficient of friction) = 0.4; V (final speed of the bus) = 0 m / s.

Constants: g (acceleration due to gravity) = 10 m / s ^ 2.

1) Determine the acceleration when braking the bus: m * a = Ftr = μ * m * g, whence a = μ * g = 0.4 * 10 = 4 m / s ^ 2 (the movement of the bus will be slowed down).

2) Calculate the time to stop: 0 = V0 – a * t and t = V0 / a = 12/4 = 3 s.

Answer: The bus will stop 3 seconds after the start of braking.