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.

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

gas and liquid