Question

Two unlike charges attract each other with a force of 10N. If the distance between them is doubled, the force between them is :

• A. $40N$
• B. $20N$
• C. $5N$
• D. $2.5N$

Answer 1

The correct option is D $2.5N$

We know $F=\frac{1}{4\pi {\epsilon }_0}\frac{q_1{q}_2}{r^2}=10N$

if distance is doubled.
$F_{new}=\frac{1}{4\pi {\epsilon }_0}\cdot \frac{q_1{q}_2}{(2r{)}^2}=\frac{10}{4}$

$=2\cdot 5N$