Ineed some w/ this:

a police car siren emits a frequency of 2010 hz when stationary. when it is driving toward a stationary car, the other driver hears a frequency of 2120 hz. how fast is the police car driving?

using the doppler's effect equation, i got the answer ±16.3, but that apparently isn't the correct answer.

edited: ohhh ok, i got it, answer is 17.7 whoops

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

a charge 3q is at the origin, and a charge −2q is on the positive x axis at x=a. part a where on the x-axis would you place a third charge so it would experience no net electric force? enter an expression for the exact answer, which will involve a square-root sign. (do not enter an approximate decimal answer.)

i wanna say it’s between b and d, leaning more towards b.