friedshrimp
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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.

Respuesta :

MathPhys

Answer:

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.