A train 400 m long is moving on a straight track with a speed of 84.3 km/h. The engineer applies the brakes at a crossing, and later the last car...

A train 400 m long is moving on a straight track with a speed of 84.3 km/h. The engineer applies the brakes at a crossing, and later the last car passes the crossing with a speed of 17.7 km/h. Assuming constant acceleration, determine how long the train blocked the crossing. Disregard the width of the crossing.