How does the path of water at the bottom of the can change as the water level in the can falls

Astone weighing 1.5 kilograms is resting on a rock at a height of 20 meters above the ground. the stone rolls down 10 meters and comes to rest on a patch of moss. the gravitational potential energy of the stone on the moss is joules.

Two 2.0-cm-diameter disks face each other, 1.0 mm apart. they are charged to ±10 nc. what is the electric field strength between the disks? a proton is shot from the negative disk toward the positive disk. what launch speed must the proton have to just barely reach the positive disk?

What would occur if the index of refraction of a material was less than n=1? the speed of light would increase to a speed larger than the maximum speed of light in a vacuum. the light wave would not bend at all though the material. the light wave would not be able to refract and would instead reflect off of the material. the speed of light would reduce to values close to 0 m/s.