Answer to Question #294422 in Classical Mechanics for Dilani

Question

A train is scheduled to travel with a velocity of 72 kmh-1 in a certain limit of its route. Due to renovation the

train had to travel 1km of the above limit with a velocity of 9 kmh-1.If the train travelled 1575m while

reducing velocity from 72 kmh-1to 9 kmh-1 and 3150m while increasing velocity from 9 kmh-1 to 72 km h-1

, how late will the train be?

Answer 1

$\Delta t=t_2-t_1=\frac{2s_1}{v_2+v_1}+\frac{s_2}{v_1}+\frac{2s_3}{v_2+v_1}-\frac{s_1+s_2+s_3}{v_2}=8.9$ min.