Question

Positively charged point objects $1,2$, and $3$ are pictured below located exactly on meter marks. Object $1$ exerts a force of $48N$ on object $2$.
How much force does object $1$ exert on object $3$?

• A. $48N$
• B. $24N$
• C. $12N$
• D. $6N$
• E. $3N$

Answer 1

The correct option is E $3N$

By Coulomb's law, the force between two charge objects 1 and 2 is $F_{21}=\frac{k{q}_1{q}_2}{r^2}$

We assume that all positive charges are same i.e $q$ so, $48=\frac{kqq}{2^2}$ or $k{q}^2=192$

The force on 3 due to 1 is $F_{31}=\frac{kqq}{8^2}=\frac{192}{64}=3N$