# Physics

A train 500 m long is moving on a straight track with a speed of 84.2 km/h. The engineer applies the brakes at a crossing, and later the last car passes the crossing with a speed of 16.4 km/h. Assuming constant acceleration, determine how long the train blocked the crossing.Disregard the width of the crossing.

1. distance engineer moved = 500 m = .5 km

average speed = (84.2 +16.4)/2 = 50.3
km/hr
(during constant acceleration you can use the average of first and last for the distance and time)

time = distance/speed = .5km / 50.3 km/hr

= .00994 hours
* 3600 = 35.8 seconds

posted by Damon

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