Question

A car horn emits a frequency of 400 hz. A car traveling at 20.0 m/s sounds the horn as it approaches a stationary pedestrian. What frequency does the pedestrian hear? The speed of sound in air is 343 m/s a) 425 hz b)450 c)375 d)400 e)200

Answer 1

`f =425 \ Hz`

Step-by-step explanation:

given,

Speed of sound = 343 m/s

speed of the car = 20 m/s

frequency of horn = 400 Hz

frequency of the sound pedestrian will hear = ?

using formula

`f = (v)/(v-v_s)f_0`

`f= (343)/(343 -20)(400)`

`f= (343* 400)/(323)`

`f=1.062 * 400`

`f =424.76`

`f =425 \ Hz`

The frequency of the sound pedestrian will hear is equal to
`f =425 \ Hz`