Explanation: When an object emitting sound is moving, it occurs a phenomenon called Doppler shift or Doppler effect. What happens is that the sound gets higher when the moving object comes closer the observer and becomes lower after it passes, This change is due to the quantity of waves that passes through an area in an unit of time.

The formula to calculate the Doppler effect is as follows

f = ( $\frac{c}{c+Vs}$ ) · f₀

f is the observed frequency;

c is the speed of sound;

Vs is velocity of the source;

f₀ is the emitted frequency of source;

Substituting and calculating,

f = $\frac{340}{340+30}$ · 300

f = 275.675 Hz

Thus, the frequency heard by the police officer is 275.675Hz.

8 0

3 years ago

A child swings on a playground swing. How many times does the child swing through the swing's equilibrium position during the co

Karolina [17]

<h2>The child swing through the swing's equilibrium position 6 times during the course of 3 periods.</h2>

Explanation:

One period means time taken to complete one revolution.

In case of swings in one period time it travels the same position through two times.

Here we need to find how many times does the child swing through the swing's equilibrium position during the course of 3 period(s) of motion.

For 1 period = 2 times

For 3 periods = 3 x For 1 period

For 3 periods = 3 x 2 times

For 3 periods = 6 times

The child swing through the swing's equilibrium position 6 times during the course of 3 periods.

3 0

3 years ago