The two trains move evenly one after the other. The speed of the first is 80 km / h, and the speed of the second

| August 17, 2021 | education

The two trains move evenly one after the other. The speed of the first is 80 km / h, and the speed of the second is 60 km / h. Determine the speed of the second train relative to the first.

V1 = 80 km / h.

V2 = 60 km / h.

V12 -?

According to the law of relativity of motion, the speed of the second train relative to the fixed frame of reference V2 is equal to the vector sum: the speed of the moving frame of reference relative to the fixed frame of reference V1 and the speed of the second train relative to the first train V21: V2 = V1 + V21.

V21 = V2 – V1 – vector.

Let us draw a coordinate axis oh, directed in the direction of the movement of trains.

OH: V21 = V2 – V1.

V21 = 60 km / h – 80 km / h = – 20 km / h.

The speed of the second train relative to the first will be directed in the opposite direction of their movement, the second train will approach the first.

Answer: the speed of the second train relative to the first is V21 = 20 km / h.



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