For a particle of mass m and charge q moving in a circular path in a magnetic field B, find how does its kinetic energy depend on the radius of the curvature of its path r.

(A) kinetic energy of a particle is proportional to 1/r.
(B) kinetic energy of a particle is proportional to r^2
(C) kinetic energy of a particle is proportional to 1/r^2.
(D) kinetic energy of a particle is proportional to r.

Phase changes are chemical changes. true or false

The ultracentrifuge is an important tool for separating and analyzing proteins. because of the enormous centripetal accelerations, the centrifuge must be carefully balanced, with each sample matched by a sample of identical mass on the opposite side. any difference in the masses of opposing samples creates a net force on the shaft of the rotor, potentially leading to a catastrophic failure of the apparatus. suppose a scientist makes a slight error in sample preparation and one sample has a mass 10 mg larger than the opposing sample. if the samples are 12 cm from the axis of the rotor and the ultracentrifuge spins at 70,000 rpm, what is the magnitude of the net force on the rotor due to the unbalanced samples? ( be thorough on your answer)

How much energy must a refrigerator absorb from 225 g of water so that the temperature of the water will drop from 35°c to 5°c