A train 100 meters long moving at a speed of 50 km/h crosses a train 120 metres long coming from opposite direction in 6 seconds. What is the speed of second train in km/h?
Approach (closing speed) speed is 50+x
in 6 seconds at this speed the trains must cover 100 m + 120 m = 220 m
(it is like holding one completely still..... when the engines meet the moving train must move 100 m to get the 'caboose' to the nose of the non-moving train....then an ADDITIONAL 120 m to get that caboose the end of the non-moving train....do you see?)
220 m /1000 m/km / (6 sec / 3600 sec/hr) = 50 +x km/hr
x = 82 km/hr