A particle of mass m and charge q moves with a constant velocity v along the negative x−direction. It enters a region containing a uniform magnetic field B directed along the negative y−direction, extending from x=a to x=b. What is the minimum value of v required so that the particle can just enter the region x>b?

qbB/m q(b-a)B/m qaB/m q(b+a)B/m

q(b-a)B/m

Velocity : v = \(\frac{qBr}{m}\) r = b - a