Explanation:
For this question the magnetic force provides the force required for the circular motion
Equating
Magnetic force = centripetal force
Bqvsinx = mv^2/r
as magnetic field is perpendicular x=90
Bqvsin90 = mv^2/r
Bq = mv/r
B= mv/rq
Then replace r= 0.6 , v= 2.1ms and mp from formula sheet and you can obtain B which is magnetic field intensity