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I keep getting this wrong! Help please! An ambulance is traveling East at 20m/s.

ID: 1596683 • Letter: I

Question

I keep getting this wrong! Help please!

An ambulance is traveling East at 20m/s. The siren emits a fixed frequency of 200Hz. 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 200Hz, higher than 200Hz, or lower than 200Hz. I really suggest drawing a picture to help sort this out. Lower A car driving East at a speed of 15m/s. The car is ahead of the ambulance. Higher A car sitting stationary at the side of the road watching the oncoming ambulance. Same A car driving East at a speed of 20m/s. The car is in front of the ambulance. Higher A car driving West at a speed of 25m/s. The car is moving towards the ambulance.

Explanation / Answer

The apparent frequeny is more than the original frequency if either or both source and observer approaching other

in the first case the velocity of the observer is less than the source which is going away from the approaching observer. so, answer is lower

Same as there is no relative motion.

high as both are approaching each other.

higher as the source is approaching.