Two objects, A with charge +Q and B with charge +4Q, are separated by a distance r. The magnitude of the force exerted on the second object by the first is F. If the first object is moved to a distance 2r from the second object, what is the magnitude of the electric force on the second object? A. F/4.
B. F/2.
C. F.
D. 2F.
E. 4F.

correct option is E. 4F

Explanation:

given data

A with charge = +Q

B with charge  = +4Q

magnitude of  force exerted on the second = F

distance from second object  =  2r

solution

as we know Electric force is proportional to the product of charges  

and if 1 charge become = 4 times  

and since distance is half

so the force increases by 4 times

and

force = k ×       .......................1

so force will be 4 time

so correct option is E. 4F

an obstruction

f=ma newton

f=100x2.5=250n