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Im having lots of problems with this question..

A car moving at 40m/s and a truck moving at 15m/s travel along the same straight road. The car's horn has a natural frequency of 400Hz. What is the change in the frequency observed by the truck as the car passes the truck? Assume the car and the truck are traveling ( a) in the same direction and ( b) in opposite directions

Im using the car as the source, and the truck as the observer. The speed of sound is 340 m/s.

The solutions I got are:

a) [(340 + 15)/(340 - 40)] 400

b) [(340 - 15)/(340 + 40)] 400

according to the teachers answers, they are wrong..

Thanks in advance :)

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# Homework Help: Doppler Effect Question

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