Question

A bullet of mass m and charge q is fired towards a solid uniformly charged sphere of radius R and total charge +q. If it strikes the surface of sphere with speed u, find the minimum speed u so that it can penetrate through the sphere. (Neglect all resistance forces or friction acting on bullet except electrostatic forces)

• A. $\frac{q}{\sqrt{2\pi {\epsilon }_{0}mR}}$
• B. $\frac{q}{\sqrt{4\pi {\epsilon }_{0}mR}}$
• C. $\frac{q}{\sqrt{8\pi {\epsilon }_{0}mR}}$
• D. $\frac{\sqrt{3}q}{\sqrt{4\pi {\epsilon }_{0}mR}}$

Answer 1

The correct option is B $\frac{q}{\sqrt{4\pi {\epsilon }_{0}mR}}$