A siren emitting sound of frequency 1000 Hz approaches a ...

[charchew]

A siren emitting sound of frequency 1000 Hz approaches a stationary observer at one-half the speed of sound. The observer hears a frequency of
 
  A) 1000 Hz
  B) 2000 Hz.
  C) 500 Hz.
  D) 1500 Hz.
  E) none of the above.

Question 2

A particle of charge +2q is placed at the origin and particle of charge -q is placed on the x-axis at x = 2a. Where on the x-axis can a third positive charge be placed so that the net electric force exerted on it is zero?
 
  A) 3.4a
  B) 6.8a
  C) 8.6a
  D) 9.3a
  E) 1.0a

[mammy1697]

Answer to Question 1

B

Answer to Question 2

B

[charchew]

TYSM

[jojobee318]

Gracias!