1. A passenger car runs on the parallel track at the speed of 30m / s, and a freight car comes face to face on the adjacent parallel track at the speed of 40m / s. what is the speed of the passenger sitting by the window in the passenger car when he sees the freight car passing in front of his eyes? What is the formula of average velocity? Can you explain this sentence, especially the following formula? Combined with speed = relative speed. Formula: same subtraction different addition, positive and negative

1. It is known that V1 = 30m / s
v2=40m/s
Find v
v=v1+v2=30+40=70m/s
2.v=s/t
If two moving objects move in the same direction, their relative velocities will be subtracted. If they move in the opposite direction, they will be added

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