# physics

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A train on one track moves in the same direction as a second train on the adjacent track. The first train, which is ahead of the second train and moves with a speed of 31.3 m/s, blows a horn whose frequency is 124 Hz. If the frequency heard on the second train is 136 Hz, what is its speed?

• physics -

F = ((V + Vr) / (V + Vs)) * Fo.
F=((343 + Vr) / (343 + 31.3)) * 124=136
F = ((343 + Vr) / 374.3)) * 124 = 136,
F = 42532 + 124Vr ) / 374.3 = 136,
F = 42532 + 124Vr = 50904.8,
124Vr = 50904.8 - 42532,
124Vr = 8372.8,

Vr = 8372.8 / 124 = 67.5 m/s.

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