Question

The nucleus of helium atom contains two protons that are separated by distance $3.0 \times 10^{-15}\, m$. The magnitude of the electrostatic force that each proton exerts on the other is

• A. $20.6 \,N$
• B. $25.6 \,N$
• C. $15.6 \,N$
• D. $12.6 \,N$

Answer 1

Answer: (B)

Charge of proton is $q_p = 1.6 \times 10^{-19}\, C$
Distance between the protons is, $r = 3 \times 10^{-15}\, m$
The magnitude of electrostatic force between protons is
$F_{e}=\frac{q_{p}\,q_{p}}{4\pi\varepsilon_{0}r^{2}}$
$=\frac{9\times10^{9}\times1.6\times10^{-19}\times1.6\times10^{-19}}{\left(3\times10^{-15}\right)^{2}}$
$=25.6\,N$