A train 483 m long is moving on a straight track with a speed of 42.4 m/s. The engineer applies the brakes at a crossing, and later the last car passes the crossing with a speed of 8.6 m/s. Assuming constant acceleration, determine how long the train blocked the crossing. Disregard the width of the crossing. Answer in units of s.

Question

Joselyn Miller

Physics

7 May, 20:22

A train 483 m long is moving on a straight track with a speed of 42.4 m/s. The engineer applies the brakes at a crossing, and later the last car passes the crossing with a speed of 8.6 m/s. Assuming constant acceleration, determine how long the train blocked the crossing. Disregard the width of the crossing. Answer in units of s.

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Answers (1)

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Madilyn Crosby · Answer 1

18.9 seconds

Explanation:

For the last car, we're given the information:

x₀ = 0 m

x = 483 m

v₀ = 42.4 m/s

v = 8.6 m/s

We need to find the time, t.

First, we find the acceleration.

v² = v₀² + 2a (x - x₀)

(8.6) ² = (42.4) ² + 2a (483 - 0)

a = - 1.784

Now, we find the time:

v = at + v₀

8.6 = (-1.784) t + 42.4

t = 18.9

The train blocks the crossing for 18.9 seconds.