Answer:
The velocity of the police car is, v = 17.798 m/s
Explanation:
Given data,
The actual frequency of the siren, f = 2010 Hz
The observed frequency of siren is, f' = 2120 Hz
The velocity of the observer, v' = 0 m/s
The velocity of the source, v = ?
The formula for Doppler effect,

Where,
V - velocity of sound waves in air.

Substituting the given values,

v = 17.798 m/s
Hence, the velocity of the police car is, v = 17.798 m/s
I think the answer is c chemical change
Answer: D. They are the coldest stars.
Explanation:
Answer:
angular frequency of the table must be same as the frequency of the projection of the gum on the wall
Explanation:
Since we know that the projection on the wall is the vertical component of the position of the gum on the rotating table
So here we will say

so the angle made by the radius vector depends on the angular frequency of the disc by which it is rotating
So we can say

so here we can say

so here we can say that
angular frequency of the table must be same as the frequency of the projection of the gum on the wall