The electrostatic force between two charges Q1 and q is given by

where 
ke is the Coulomb's constant
Q1 is the first charge
q is the second charge
r is the distance between the two charges
Re-arranging the formula, we have

and since we know the value of the force F, of the charge Q1 and the distance r between the two charges, we can calculate the value of q:

And since the force is attractive, the two charges must have opposite sign, so the charge q must have negative sign.
 
        
        
        
Answer:
There are three basic categories of musical instruments: percussion, wind, and stringed instruments. Most musical instruments use resonance to amplify sound waves and make sounds louder. In a musical instrument, the whole instrument and the air inside it may vibrate when the head of the drum is struck.
 
        
             
        
        
        
Which one if you want independent variable meaning that means  variable (often denoted by x ) whose variation does not depend on that of another.
 
        
             
        
        
        
the answer is C. It allows citizens to submit anonymous tips to the police.