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Sun 6 Jan, 2013 01:53 pm

Can you help me in this word problem for physics?

There are two cities (A and B). On a train from A to B, every 50 minutes the train meets another train going in the opposite direction (from B to A), on a parallel track. Constant speed of the train(A to B) is 90 km/hr and the speed of all approaching trains is 120km/hr (B to A). Someone assumes that the approaching trains leave her home town at regular intervals and travel at constant speed, and is able to calculate the time period between their departures. Duplicate her calculations (answer in minutes)

@greatestever298,

Trains coming towards your train are at 50min intervals. In 50 minutes, your train goes 90km/hr * 5/6 hour = 75km. The approaching train goes 120 km/hr * 5/6 hr = 100 km. This means the two oncoming trains started 175 km apart. Since the speed of the approaching trains is 120 km/hr = 2 km/min, the time period is 175 km / 2km/min.