The force of gravity between a planet and its moon is 371 N. If the planet has a mass of 4 x 10^22 kg and the moon has a mass of 5 x 10^5 kg, what is the distance between their centers?

The size (radius) of an oxygen molecule is about 2.0 ×10−10m. make a rough estimate of the pressure at which the finite volume of the molecules should cause noticeable deviations from ideal-gas behavior at ordinary temperatures (t= 300k ). assume that deviatons would be noticeable when volume of the gas per molecule equals the volume of the molecule itself.