If a repulsive force of 12 N is experienced by two charges 10 cm apart, find the magnitude of the force when they are now 15 cm apart.
A
5.93N
B
5.33N
C
5.45N
D
6.09N
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Using Coulomb’s law, the force is inversely proportional to the square of the distance:
F\(_1\) ∝ \(\frac{1}{r_1^2}\)
k = F\(_1\) r\(_1^2\) = F\(_2\)r\(_2^2\)
F\(_2\) = F\(_1\) x \((\frac{r_1}{r_2})^2\)
F\(_2\) = 12 x \(\frac{4}{9}\) (reduce 10/15 and square the result)
F\(_2\) = 5.33N
Source: Myschool Past Questions Archive (Record #78284)