Question

n the figure ,if net force on Q is zero then value of Q/Q is

Answer 1

value of Q/q is 2√​2​​​.

Answer 2

your question is incomplete ,
Well, I attached figure as mentioned in figure .

net force on Q is zero , it means Q and q are in opposite nature .
Let Q is positive nature and q is negative nature
Then, force between Q and Q will be repulsion,
And force between Q and q will be attraction,

Now, net force act on Q =net force act by q - net force act by Q on Q = 0
net force act by q on Q = net force act by Q on Q
$\sqrt{[\frac{KqQ}{r^2}]^2+[\frac{KqQ}{r^2}]^2}=\frac{KQQ}{(\sqrt{2r})^2}\\\\\sqrt{2}\frac{KqQ}{r^2}=\frac{KQ^2}{2r^2}\\\\2\sqrt{2}qQ=Q^2\\\\2\sqrt{2}=\frac{Q}{q}$

Hence, answer is Q/q = 2√2