Still considering the system of the comet plus the star, which of the following statements are correct? a. the sum of the kinetic energy of the system plus the gravitational potential energy of the system is a positive number. b. along this path the gravitational potential energy of the system is never zero. c. the gravitational potential energy of the system is inversely proportional to the square of the distance between the comet and star. d. at every location along the comet's path the gravitational potential energy of the system is negative. e. the sum of the kinetic energy of the system plus the gravitational potential energy of the system is the same at every location along this path.

People with normal vision cannot focus their eyes underwater if they aren't wearing a face mask or goggles and there is water in contact with their eyes. in a simplified model of the human eye, the aqueous and vitreous humors and the lens all have a refractive index of 1.40, and all the refraction occurs at the cornea, whose vertex is 2.60 cm from the retina.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 2.05cm in front of the eye.)

Which statements did both aristotle and ptolemy assume? check all that apply.

Atoms containing radioactive nuclei are called