In which of the following situations is the photoelectric effect being demonstrated? A.
The color of a substance is determined by the wavelength of electromagnetic radiation that is reflected off of its surface.
B.
A photon of light travels at the speed of light in a vacuum but moves slightly slower through a medium made of matter.
C.
An electron moves through a sea of electrons within a block of aluminum atoms when a voltage is applied to the metal.
D.
An electron within an atom absorbs energy when it is hit by a photon and jumps to a higher energy level within the atom.

What is the rate of change in a objects position?

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)

You can decrease the resistance of a length of wire by