Around the turn of the twentieth century, inventor robert shuman was engineering products that used energy directly from the sun to power motors and farms. he stated that coal and oil would eventually run out and that humans needed to learn how to use the more-abundant energy resource of the sun. during which stage of technological design did shuman identify that using oil and coal would be a problem?

As you move from right to left on the periodic table the atomic radius fill in the blank

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.

An object resting on a table weighs 100 n. with what force is the object pushing on the table? with what force is the table pushing on the object? explain how you got your answer.