A neutral particle is at rest in a uniform magnetic field `B`. At time `t = 0` it decays into two charged particles, each of mass `m`.
(a) If the charge of one of the particles is `+q`, what is the charge of the other?
(b) The two particles move off in separate paths, both of them lie in the plane perpendicular to `B`. At a later time, the particles collide. Express the time from decay until collision in terms of `m, B` and `q`.

Answer

`(pim)/(qB)`

Explanation

Since, total charge is zero initially thus the two particle will be of opposite charges.Initially the neutral particle is at rest, so both will have same speed.As both particle move in opposite directions. Magnetic force on them will be in the same direction and of same magnitude.
Using `R=(mV)/(qB)`, both will be moving in the circle of same radius.So they will meet at point `Q`.i.e. diametrically opposite to starting point `P`.So time taken will be