The train is moving at a speed of 20 m / s. What will be the speed of the train after braking

The train is moving at a speed of 20 m / s. What will be the speed of the train after braking, occurring with an acceleration of 2m / s ^ 2, for 20 s.

V0 = 20 m / s.

t = 20 s.

a = 2 m / s2.

V -?

According to the definition, the acceleration of the body’s motion, and is called a vector physical quantity, which shows the rate of change in speed and is determined by the formula:

a = (V – V0) / t, where V0, V are the initial and final speed of movement, a is the acceleration of the body during movement, t is the braking time.

Let us express the final speed of movement: V = V0 + a * t.

But since during deceleration the acceleration of the body is directed in the opposite direction of motion, the acceleration of the body must be with the sign “-“, the speed of the body decreases.

V = V0 – a * t.

V = 20 m / s – 2 m / s2 * 20 s = – 20 m / s – we see that the final speed cannot be negative, the train could not start moving in the opposite direction.

Let’s find the braking time: t1 = V0 / a.

t1 = 20 m / s / 2 m / s2 = 10 s.

The braking time of the train under such conditions is t1 = 10 s.

Answer: the final speed of the train when braking is V = 0 m / s.