In separate experiments, a large number of particles (all with the same charge, but with a wide variety of masses and speeds) are fired into a region containing a uniform magnetic field. The velocities of the particles are all perpendicular to the field. What do the particles that move in orbits of the same radius have in common

  they have the same mass

Explanation:

The force applied by the field is a function of the charge and velocity, so the acceleration experienced by a particle will be dependent upon its mass. Particles in orbits with the same radius are exhibiting the same acceleration, so must have the same mass.

a=d/t

a="triangle"v/t

explanation:

a = acceleration