Question

there are two charged particles q and 4q at 3m distance the force on Q charge kept at P is

Answer 1

Hi there
The force on Q due to q will be repulsive as both of them are positively charged
or,F1=k(q)(Q)/1²=kqQ towards right, where k=1/(4πε)=9 x 10⁹Nm²/C² 
The force on Q due to 4q will also be repulsive as both of them are positively charged.
or,F2=k(4q)(Q)/2²=4kqQ/4=kqQ towards left.
now net Force=F1+F2=(KqQ)+(-kqQ)=0
since total force on charge Q is 0.So Q is in equilibrium.

Answer 2

Answer: Zero

Explanation:

Force on Q due to 4q

F1 = kQ4q/2^2 = kQ4q/4 = kQq

Force on Q due to q

F2 = kQq/1^2 = kQq

As the direction of the force is opposite.

So, Net force = kQq - kQq = 0