Homework Help: physics

Posted by maria on Tuesday, November 15, 2011 at 6:31pm.

A policeman with a very good ear and a good understanding of the Doppler effect stands on the shoulder of a freeway assisting a crew in a 40-mph work zone. He notices a car approaching that is honking its horn. As the car gets closer, the policeman hears the sound of the horn as a distinct G3 tone (196 Hz). The instant the car passes by, he hears the sound as a distinct D3 tone (147 Hz). He immediately jumps on his motorcycle, stops the car, and gives the motorist a speeding ticket. How fast was this car going? (Assume that the speed of sound is 340 m/s.)

physics - bobpursley, Tuesday, November 15, 2011 at 7:18pm
196=f1/(340-Vcar)
147=f(1/(340+vcar)

dividing the first equation by the second

196/147=(340+vcar)/(340-Vcar)

4/3 (340-Vcar)=340+Vcar

1/3 340=7/3 Vcar

vcar=340/7=you do it... m/s That is almost 109mph

Answer this Question

Related Questions

Economic - A Giffin good is not correctly described by which of the following? A...
Physics - A speeder traveling at 41 m/s passes a motorcycle policeman at rest at...
need diagram of an ear - Does anybody know where I can find a very simple ...
physics - A speeder traveling at 47 m/s passes a motorcycle policeman at rest at...
physics - A speeder traveling at 38 m/s passes a motorcycle policeman at rest at...
Physics - A speeder traveling at 40 m/s passes a motorcycle policeman at rest at...
Physics HELPPPP - A speeder traveling at 37 m/s passes a motorcycle policeman at...
English - How are you? Not so well. Not so good. Not so fine. Not very good. Not...
Physics - Question about doppler effect: How do you solve when it gives you ...
physics - Explain the Doppler Effect?

For Further Reading

First Name:
School Subject:
Answer: