A. The four isotopes of lead are shown below, each with its percent by mass abundance, the composition of its nucleus and atomic masses. Using this data, calculate the average atomic mass of lead.
82p, 122n, 1.37%, 203.97 amu
82p, 124n, 26.26%, 205.97amu
82p, 125n, 20.82%, 206.98amu
82p, 126, 51.55%, 207.97 amu

The crust of earth may a- continets and ocean floors. b-continents only. c-layers of sedimentary rocks and continents. d-all of the above

Hot air balloons float in the air because of the difference in density between cold and hot air. in this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. to do this, use the following variables and make these assumptions: the combined weight of the pilot basket together with that of the balloon fabric and other equipment is w. the volume of the hot air inside the balloon when it is inflated is v. the absolute temperature of the hot air at the bottom of the balloon is th (where th> tc). the absolute temperature of the cold air outside the balloon is tc and its density is ďc. the balloon is open at the bottom, so that the pressure inside and outside the balloon is the same. as always, treat air as an ideal gas. use g for the magnitude of the acceleration due to gravity.

Which best describes how johannes kepler developed his laws of planetary motion