Question

Two spherical ball of mass 1 kg each and both carry a charge of magnitude 1 C. Compare the two force gravitational forces $F_G$ and electrostatic force $F_E$ between the spherical balls.

• A. $F_E<F_G$
• B. $F_E=F_G$
• C. $F_E>F_G$
• D. If the charges on the spheres are of the same sign, then $F_E>F_G$ ; but if the charges on the spheres are of opposite sign, then $F_E<F_G$
• E. Cannot be determined without knowing the distance between the spheres

Answer 1

Answer: (C)

$F_E>F_G$

The gravitational force, $F_G=\frac{G{m}_1{m}_2}{r^2}=\frac{G\left(1\right)\left(1\right)}{r^2}$

The electrostatic force, $F_E=\frac{1}{4\pi {ϵ}_0}\frac{q_1{q}_2}{r^2}=\frac{1}{4\pi {ϵ}_0}\frac{\left(1\right)\left(1\right)}{r^2}$

Since $G=6.67\times {10}^{-11}{m}^{3}k{g}^{-1}{s}^{-2}$ and $\frac{1}{4\pi {ϵ}_0}=9\times {10}^{9}N{m}^2{C}^{-2}$ so $F_E>F_G$