The frequency of bird chirping hear by hiran will be 1.77 kHz.
<u>Explanation:</u>
As per Doppler effect, the observer will feel a decrease in the frequency of the receiving signal if the source is moving away from the observer. So the shifted frequency is obtained using the below equation:

Here , c is the speed of sound, Vs is the velocity of source with which it is moving away. f is the original frequency of source and f' is the frequency shift heard by the observer.
As here, f = 1800 Hz, Vs= 6 m/s and c = 343 m/s, then

So, the frequency of bird chirping hear by hiran will be 1.77 kHz.
Answer:
Impulse = 80Ns
Explanation:
Given the following data;
Mass = 3kg
Force = 20N
Time = 4 seconds
To find the impulse experienced by the object;
Impulse = force * time
Impulse = 20*4
Impulse = 80Ns
Therefore, the impulse experienced by the object is 80 Newton-seconds.
Hello
the best answer is c
The wave phenomenon known as "destructive interference".