An 80% efficient pump with a power input of 20 hp is pumping water from a lake to a nearby pool at a rate of 1.5 ft3/s through a constant-diameter pipe. the free surface of the pool is 80 ft above that of the lake. determine the mechanical power used to overcome frictional effects in piping.

Light that is polarized along the vertical direction is incident on a sheet of polarizing material. only 96% of the intensity of the light passes through the sheet and strikes a second sheet of polarizing material. no light passes through the second sheet. what angle does the transmission axis of the second sheet make with the vertical?

An object weighs 40n in air, weighs 20n when submerged in water and 30n when submerged in a liquid of unknown density. what is the density of the liquid?

Which planets are visible without a telescope