Question

If an electron has an initial velocity in a direction different from that of an electric field, the path of the electron is

• A. a straight line
• B. a circle
• C. an ellipse
• D. a parabola

Answer 1

Answer: (D)

a parabola

Answer 2

The path is a parabola, because initial velocity can be resolved into two rectangular components, one along $\vec{E}$ and other $\bot$ to $\vec{E}$. The former decreases at a constant rate and latter is unaffected. The resultant path is therefore a parabola.