Question

A neutral particle is initially at rest in a uniform magnetic field B as shown in the diagram. The particle then spontaneously decays into
two fragments, one with a positive charge +q and mass 3m and the
other with a negative charge –q and mass m. Neglecting the
interaction between the two charged particles and assuming
that the speeds are much less than speed of light, the time
after the decay at which the two fragments first meet is [Data :
$q=1\mu C,B=2\pi \mu T,m={10}^{–15}kg$ Both the charges have initial velocities in x-y plane]

• A. $250\mu s$
• B. $500\mu s$
• C. $750\mu s$
• D. $1000\mu s$

Answer 1

The correct option is C $750\mu s$

momentums are same and opposite.
$2\pi r=vt+\frac{v}{3}t$