A neutral particle is at rest in a uniform magnetic field `vecB`.At `t=0`,particle decays into two particles each of mass `m` and one of them having charge `q` Both of these move off in separate paths lying in plane perpendicular to `vecB`.A later time,the particles collide.Find this time of collision neglecting the interaction force.

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