In: Physics
1)What is the force between two equal charges (1 Coulomb) that are separated by a distance of 1 km? 2)Suppose that the charge of one of the charges in problem #1 is reduced to half of its original value. How does the new force compare to the original force?
1)
Force between two charges is calculated by Coulomb's Law.

Here, 
 is force between two charges 
 and 
 separated by distance 
 and 
 is Coulomb's constant.
Substitute 1 C for 
 & 
, 1000 m for 
 and 
 for  
in above equation of force.

N
2)
Let value of charge of 
 be reduced to half and it becomes 
.

Here, 
 is force between two charges 
 and 
 separated by distance 
.
Substitute 1 C for 
, 0.5 C for  
,
1000 m for 
 and 
 for  
in above equation of force.

N
Thus, when the charge of one of the charges is reduced to half of its original value, force will also be reduced to half.