The car moves along the horizontal section of the track at a speed of 20 m / s. determine the minimum time of movement

The car moves along the horizontal section of the track at a speed of 20 m / s. determine the minimum time of movement of the vehicle to a complete stop during braking, if the coefficient of friction of the wheels on the road is 0.4. the acceleration of gravity is considered equal to 10m / s2

V0 = 20 m / s.
V = 0 m / s.
g = 10 m / s2.
μ = 0.4.
t -?
We express the braking time t from the formula for the acceleration of movement: t = (V0 – V) / a.
Since the car has stopped, its final speed V = 0 m / s.
The formula will take the form: t = V0 / a.
Let’s write 2 Newton’s law when braking a car: m * a = Ftr.
Ftr = μ * m * g.
m * a = μ * m * g.
a = μ * g.
The formula for determining the braking time will take the form: t = V0 / μ * g.
t = 20 m / s / 0.4 * 10 m / s2 = 5 s.
Answer: the minimum time for the vehicle to move to a complete stop is t = 5 s.