1) How is density different than mass?

Mass is a measure of how much matter there is within an object, typically given in grams. Mass is not affected by gravity, so a given object would have the same mass on earth as in outer space. Density is the amount of mass in an object per a certain amount of volume

Explanation:

If θ=90°, the force acting on the particle is the maximum possible and the direction of the force is perpendicular to the path of the particle. The particle then moves along a circular path with the force acting as the centripetal force.

The magnetic field does no work, so the kinetic energy and speed of a charged particle in a magnetic field remain constant. The magnetic force, acting perpendicular to the velocity of the particle, will cause circular motion.