henrietta leavitt first showed the relationship between the mass and luminosity of cepheids and their period of pulsation; the brighter, the longer this period.

"an open tank has the shape of a right circular cone. the tank is 6 feet across the top and 5 feet high. how much work is done in emptying the tank by pumping the water over the top edge? note: the density of water is 62.4 lbs per cubic foot."

The necleus of an atom is made up of what subatomic particles?

Which compound is held together by the electrostatic force between two ions? a. co2 b. cci4 c. h2s d. mgf2