A person pushes a 27.4 kg car at a constant velocity of 17.1 m/s across a horizontal floor for 78.3 s. Find the energy dissipated by the
frictional force ?
(given that the coefficient of kinetic friction Hk = 0.4)

Energy =

Awelder using a tank of volume 7.50×10^-2 m^3 fills it with oxygen (with a molar mass of 32.0 g/mol ) at a gauge pressure of 3.30×10^5 pa and temperature of 37.1 ∘c. the tank has a small leak, and in time some of the oxygen leaks out. on a day when the temperature is 23.1 ∘c, the gauge pressure of the oxygen in the tank is 2.00×10^5 pa . a) find the initial mass of oxygen. b) find the mass of oxygen that has leaked out.