What is an accretion disk? a) any flattened disk in space, such as the disk of the milky way galaxy. b) a disk of hot gas swirling rapidly around a white dwarf, neutron star, or black hole. c) a stream of gas flowing from one star to its binary companion star. d) a disk of material found around every white dwarf in the milky way galaxy.

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?

You are driving to the grocery store at 20 m/s. you are 110m from an intersection when the traffic light turns red. assume that your reaction time is 0.50s and that your car brakes with constant acceleration. how far are you from the intersection when you begin to apply the brakes? what acceleration will bring you to rest right at the intersection? how long does it take you to stop after the light changes? the known values: vi=20m/s xi=110m t=.50s vf=0m/s xf=0m a=?