Velocity is Perpendicular to Magnetic Field |Questions

Which particle will have minimum frequency of revolution when projected with the same velocity perpendicular to a magnetic field ?

If an alpha- particle moving with velocity 'v' enters perpendicular to a magnetic field then the magnetic force acting on it will be-

Magnetic Force on Charge||Path OF Charge Particle Moving Perpendicular to Magnetic Field||Charge Particle Moving Along Magnetic Field

Magnetic Force on Charge||Path of Charged Particle Moving Perpendicular to Magnetic Field||Charged Particle Moving Along Magnetic Field

An electron, a proton and a He^(+) ion projected into a magnetic field with same kinetic energy, with velocities being perpendicular to the magnetic field. The order of the radii of circles traced by them is :

A proton of mass m and charge q enters a region of uniform magnetic field of a magnitude B with a velocity v directed perpendicular to the magnetic field. It moves in a circular path and leaves the magnetic field after completing a quarter of a circle. The time spent by the proton inside the magnetic field is proportional to: