Question

An electron of mass M kg and charge coulomb travels from rest through a potential difference of V volt. The final, y velocity of the electron is (in m7s)

• A. $\frac{2eV}{M}$
• B. $\frac{2MV}{e}$
• C. $\sqrt{\frac{2eV}{M}}$
• D. $\sqrt{\frac{2MV}{e}}$

Answer 1

Answer: (C)

Energy gained by an electron
$= q \Delta V$ $= V \times e$
this energy is in the from kinetic energy
$\Rightarrow \frac{1}{2} Mv _{ f }^{2}= V \times e$
$\Rightarrow v _{ f }^{2}=\frac{2 eV }{ M }$
$\Rightarrow v _{ f }=\sqrt{\frac{ 2 e V }{ M }}$