Astronomers believe that the radius of a variable star increases and decreases with the brightness of the star. suppose a variable star has an average radius of 20 million miles and changes by a maximum of 1.4 million miles from this average during a single pulsation, and that the time between periods of maximum brightness is 5.8 days. find an equation that describes the radius of this star as a function of time. (let r be the radius in millions of miles and let t be the time in days. assume that when t = 0 the radius is 20 million miles and increasing.)

The consumption of fossil fuels could be

Suppose that two tanks, 1 and 2, each with a large opening at the top, contain different liquids. a small hole is made in the side of each tank at the same depth 1.57 m below the liquid surface, but the hole in tank 2 has 2.49 times the cross-sectional area of the hole in tank 1. (a) what is the ratio ρ1/ρ2 of the densities of the liquids if the mass flow rate is the same for the two holes? (b) what is the ratio rv1/rv2 of the volume flow rates from the two tanks? (c) at one instant, the liquid in tank 1 is 14.9 cm above the hole. if the tanks are to have equal volume flow rates, what height above the hole must the liquid in tank 2 be just then?

Aphoton is absorbed by an electron that is in the n = 3 state of a hydrogen atom, causing the hydrogen atom to become ionized. very far away from the nucleus, the released electron has a velocity of 750,000 m/s. what was the wavelength of the absorbed photon?