# Physics

A light-rail commuter train blows its 200 Hz horn as it approaches a crossing. The speed of sound is 336 m/s.

a)An observer waiting at the crossing receives a frequency of 205 Hz. What is the speed of the train?

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1. Fr = ((Vs+Vr)/(Vs-Vo))*Fo = 205 Hz
((336+0)/(336-Vo))*200 = 205
((336)/(336-Vo))*200 = 205
67,200)/(336-Vo) = 205
205(336-Vo) = 67200
68,880-205Vo = 67200
-205Vo = 67200-68880 = -1680
Vo = 8.2 m/s. = Speed of the train.

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posted by Henry

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