There are 7,461,120,000 people on earth (Circa October, 2016). The average mass of a person is 60 kg. The Earth has a mass of 5.97 x 1024 kg. If all of the
people on Earth stood in one spot and jumped 1 m/s up, what is the recoil velocity
of the Earth?

With the simplified model of the eye, what corrective lens (specified by focal length as measured in air) would be needed to enable a person underwater to focus an infinitely distant object? (be careful-the focal length of a lens underwater is not the same as in air! assume that the corrective lens has a refractive index of 1.62 and that the lens is used in eyeglasses, not goggles, so there is water on both sides of the lens. assume that the eyeglasses are 1.90