Posted by Zena on .
3. A gas is confined in a 0.47-m-diameter cylinder by a piston, on which rests a weight. The mass of the piston and weight together is 150 kg. The atmospheric pressure is 101 kPa. (a)What is the pressure of the gas in kPa? (b) If the gas in the cylinder is heated, it expands, pushing the piston and weight upward. If the piston and weight are raised 0.83 m, what is the work done by the gas in kJ? What is the change in potential energy of the piston and weight?
(a) add the atmospheric pressure to (weight)/(area)
Use the combined weight, 150*g = 1470 N
P = 1470/[(pi/4)0.47^2] + 101,000 Pa
(b) work done = P* 0.83 m *(area)
P.E. change of piston and weight
= M g H
The difference is work done against the atmosphere.