What are the applications of magnetic levitation?

Afigure skater is rotating at a rate of 200 revolutions per minute. what is the angular speed, in units of rad/s? 20.9 12000 200 3.33

Because air contracts as it cools, the air pressure inside a freezer is typically lower than on the outside. why do ice cubes inside a freezer tend to shrink over time? a. the ice dissolves oxygen from the air, forming a denser crystalline matrix.b. the ice reacts chemically with carbon dioxide in the air, forming gaseous carbon compounds.c. the ice melts, and then the liquid freezes as ice crystals on the bottom of the freezer.d. the ice sublimes, and then the water vapor deposits as ice crystals on the sides of the freezer.

In a hydrogen molecule there are a total of four charges, 2 protons in the two nuclei, and 2 electrons. how many unique charge-pairs are there (without double counting)?