The bullet pierced the wall 45 centimeters thick and its speed decreased from 70 m / s

| April 8, 2021 | education

The bullet pierced the wall 45 centimeters thick and its speed decreased from 70 m / s to 200 m / s. Determine the time the bullet moved in the wall.

V0 = 70 m / s.

V = 20 m / s.

S = 45cm = 0.45m.

t -?

The bullet in the wall was moving uniformly accelerated, we find the acceleration of movement, and by the formula: a = (V ^ 2 – V0 ^ 2) / 2 * S.

a = ((20 m / s) ^ 2 – (70 m / s) ^ 2) / 2 * 0.45 m = – 500 m / s ^ 2.

The “-” sign indicates that the acceleration of the bullet against the direction of travel, the bullet in the wall is inhibited.

By definition, a = (V – V0) / t.

Let us express the time of movement of the bullet in the wall: t = (V – V0) / a.

t = (20 m / s – 70 m / s) / (- 500 m / s ^ 2) = 0.1 s.

Answer: the bullet moved inside the wall for a time t = 0.1 s.



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