The refractive index of a transparent material can be determined by measuring the critical angle when the solid is in air. if ? c= 41.3 what is the index of refraction of the material?

An asteroid is discovered in a nearly circular orbit around the sun, with an orbital radius that is 2.47 times earth's. what is the asteroid's orbital period, its "year," in terms of earth years?

Athin plate moves between two parallel, horizontal, stationary flat surfaces at a constant velocity of v = 7.5 m/s. the two stationary surfaces are spaced 4 cm apart, and the medium between them is filled with oil whose viscosity is 0.9 n·s/m2. the part of the plate immersed in oil at any given time is 2 m long and 0.5 m wide. if the plate moves through the mid-plane between the surfaces, determine the force required to maintain this motion. what would your response be if the plate was 1 cm from the bottom surface (h2) and 3 cm from the top surface (h1)? if the plate moves through the mid-plane between the surfaces, the force required to maintain the motion will be n. if the plate was 1 cm from the bottom surface (h2) and 3 cm from the top (h1) surface, the force required to maintain the motion would be n.

Idon’t quite understand this problem