A 1 km train enters a 2 km tunnel. determine the time during which any part of the train will be in the tunnel during which any part of the train will be in the tunnel if the speed of the train is 36 km / h.
L = 1 km = 1000 m – train length;
S = 2 km = 2000 m – tunnel length;
v = 36 km / h = 10 m / s – train speed.
It is required to find the time t during which some part of the train will be in the tunnel.
The point located at the beginning of the train will be in the tunnel for the time:
t1 = S / v = 2000/10 = 200 s.
At the same moment, the point located at the end of the train will enter the tunnel at a distance:
S1 = S – L1 = 2000 – 1000 = 1000 m.
This distance will be covered by the point at the end of the train in time t2:
t2 = S1 / v = 1000/10 = 100 s.
Full time: t = t1 + t2 = 200 + 100 = 300 s.
Answer: 300 seconds.
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