Tina is driving her sports car down US1, traveling 27 m/s. She sees her friend Rita up ahead, waiting to cross the street at the next intersection. Tina quickly slams down on the horn. If the horn has a frequency of 400 Hz, which of the following is the only possible frequency heard by Rita, as Tina drives toward Rita? (2 points)

Explanation:

Tina speed Vs =27m/s

Rita speed Vo = 0m/s, she is not moving

Frequency from Tina horn is 400Hz

fs = 400Hz

Frequency Rita will hear as Tina moves closer ? fo

This is a situation whereby source is moving toward observer.

Using Dopler's effect of source moving towards observer

fo = fs [V/(V—Vs)]

Where V is speed of sound

Let assume V =343m/s

Vs is source speed = 27m/s

Fs is source frequency = 400

fo = 400[343 / (343-27)]

fo = 400 [ 343/316]

fo = 400 × 1.0854

fo = 434.2Hz

As expected, since the source is moving towards the observer, we expect the observe to hear high frequency.

the answer is 46 mls because when you add the speed per second it increses the speed