How many electrons would it take to equal the mass of a proton? use two significant figures.

An object of dimensions 50 cm x 40 cm x 0.20 cm has a mass 60g. find its density in g/cm3 and kg/ m3

Tall pacific coast redwood trees can reach heights of about 100 m. if air drag is negligibly small, how fast is a sequola cone moving when it reaches the ground f it dropped from the top of a 100 m tree?

An insulated 40 ft^3 rigid tank contains air at 50 psia and 120°f. a valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 25 psia. the air temperature during this process is kept constant by an electric resistance heater placed in the tank. determine the electrical work done during this process.