Question

If 2 point charges are moved from 1mm apart to 5 mm apart, the force between them will be reduced by
A. 1/5
B. 1/25
C. 1/10
D. 1/2.5

Answer 1

\(F_A = k \dfrac{q_1q_1}{r^2}\)
\(F_B = k \dfrac{q_1q_1}{(5r)^2}\)

**reduced by** is also plain bad termonilogy :-))

\(\Delta F \%= \dfrac{F_B - F_A}{F_B} \) etc etc etc

Answer 2

U know F is inversely proportional to r^2

Answer 3

First time r=1mm

Answer 4

Second time r=5mm

Answer 5

So second time F will b reduced

Answer 6

Fb/Fa=?