An ambulance is traveling East at 20m/s. The siren emits a fixed frequency of 38

Question

An ambulance is traveling East at 20m/s. The siren emits a fixed frequency of 380Hz. Each of the following cars is traveling down the road as described. Determine if the driver of the car will hear a frequency the same as 380Hz, higher than 380Hz, or lower than 380Hz. I really suggest drawing a picture to help sort this out.

A car driving West at a speed of 25m/s. The car has already passed the ambulance.

A car driving East at a speed of 20m/s. The car is in front of the ambulance.

A car sitting stationary at the side of the road watching the ambulance moving away.

A car driving East at a speed of 15m/s. The car is behind the ambulance.

Explanation / Answer

This is all done by the Doppler Effect.

Part 1)

Since the car and ambulance are traveling away from each other, the frequency heard will be lower.

Part 2)

Since the car and ambulance are traveling in the same direction at the same speed, the frequency heard will be the same.

Part 3)

Since the ambulance is traveling away from the car, the frequency heard will be lower.

Part 4)

The ambulance is traveling away from the car since it is faster than the car in the same direction, the frequency heard will be lower.

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