PhysicsLAB: More Practice with the Doppler Practice

Refer to the following information for the next three questions.

A car is racing away from a siren at 25 m/sec. The siren is emitting a frequency of 1200 hz. The air temperature is 30ºC.

What is the speed of sound at this temperature?

What frequency is heard by the person driving the car?

How fast would he have to travel to hear a frequency that is only 85% of the siren's true frequency?

Refer to the following information for the next eight questions.

An ambulance, with its siren blaring, is racing at 38 m/sec along the interstate towards the exit for the nearest hospital. Its siren has a frequency of 1200 hz and the air temperature is 10ºC.

What is the speed of sound at this temperature?

What would be the wavelength of the siren if the ambulance were at rest?

By how much is the wavelength changed due to the siren's motion?

While the ambulance approaches, what wavelength is "heard" by those drivers who stop and pull off to the side of the road so that the ambulance can pass unhampered?

What frequency do these driver's hear?

Just as the ambulance is parallel to their position, what frequency do they hear?

After the ambulance has passed, while it continues down the interstate at the same speed, what frequency would the motorists hear?

Is the frequency change greater when the ambulance is approaching or after it has passed?

approaches

passed