Question

A particle of charge \( q \) is shot with speed \( V \) towards another fixed particle of charge \( Q \). It reaches the closest distance \( r \) and then returns. If \( q \) were shot with speed \( 2V \), then the closest distance of approach of \( Q \) is:

• A. \( r \)
• B. \( 2r \)
• C. \( \frac{r}{2} \)
• D. \( \frac{r}{4} \)

Hint:

When a charged particle moves towards another fixed charge, the closest distance of approach is inversely proportional to the speed of the particle.

Answer 1

The Correct Option is C

The closest approach is inversely proportional to the velocity of the particle. If the speed is doubled, the closest distance of approach will be halved.
Thus, the new closest distance of approach is \( \frac{r}{2} \).