The train, moving after the start of braking with an acceleration of 0.4 m / s2, stopped

The train, moving after the start of braking with an acceleration of 0.4 m / s2, stopped after 25 seconds. Find the speed of the train at the start of braking.

V = 0 m / s.

t = 25 s.

a = 0.4 m / s2.

V0 -?

According to the definition, the acceleration of the body’s motion is called a quantity that shows how quickly the speed changes 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.

Since the train stopped during braking, its final speed is 0: V = 0 m / s.

The formula for the acceleration of the body will take the form: a = – V0 / t.

V0 = a * t.

The “-” sign indicates that the acceleration of the body and the direction of motion have opposite directions.

V0 = 0.4 m / s2 * 25 s = 10 m / s.

Answer: the initial speed of the train during braking was V0 = 10 m / s.