3.112 (6^th ed)

Air in a tank is at 1 MPa and room temperature of 20C. It is used to fill an initially empty balloon to a pressure of 200 kPa, at which point the radius is 2m and the temperature is 20C. Assume the pressure in the balloon is linearly proportional to its radius and that the air in thank also remains at 20C throughout the process. Find the mass of air in the balloon and the minimum required volume of the tank.

ANS: 79.66 kg, 8.377 m^3

3.113 (6^th ed)

A cylinder is fitted with a 10-cm-diameter piston that is restrained by a linear spring (force proportional to distance) as shown below. The spring force constant is 80 kN/m and the piston initially rests on the stops, with a cylinder volume of 1 L. The valve to the air line is opened and the piston begins to rise when the cylinder pressure is 150 kPa. When the valve is closed, the cylinder volume is 1.5 L and the temperature is 80C. What mass of air is inside the cylinder?

ANS: 0.012 kg