posted by Bob .
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.
distance engineer moved = 500 m = .5 km
average speed = (84.2 +16.4)/2 = 50.3
(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