Question

A charged particle of mass 1 kg is projected with initial velocity $(3\hat{i}+4\hat{j})$ m/s in an uniform electric field, $\overrightarrow{E}=(-2.5\hat{i})$ N/C and gravitational field,$\overrightarrow{g}=(-10\hat{j})m/s^2$. What should be the value of charge so that the particle moves in straight line?

• A. 1 C
• B. 3 C
• C. 5 C
• D. 7.5 C

Answer 1

The correct option is B 3 C

For straight line motion, Net velocity and net acceleration should be in same line.
$i.e.tan\theta =\frac{4}{3}=\frac{mg}{qE}\Rightarrow q=3C$