Question

An alarm clock is dropped off the edge of a tall building. You, standing directly under it, hear a tone of 1350 Hz coming from the clock at the instant it hits the ground (you jumped out of the way at the last moment- whew!) Since you know the building is 25.0 m tall, you can find out what the frequency of the alarm would be if you had just held it in your hands. What would that frequency be?

Answer 1

Answer

Doppler effect formula when moving sound source is given by

$f=\frac{f_0 v_s}{v_s\pm v_0}$ ........ eq. 1

In case of observer is moving

$f=f_0\frac{v_s\pm v_0}{v_s}$

$f_0$ Is frequency of source.=1350nm

h= height of building

So putting all value in eq. 1 then frequency is found is

$f=1263Hz$