SP3: The piston of a vertical piston-cylinder device containing air has a mass o
ID: 1816779 • Letter: S
Question
SP3:
The piston of a vertical piston-cylinder device containing air has a mass of 60 kg and cross-sectional area of 0.04 m2. The absolute pressure of the surrounding atmosphere is 0.97 bar and the local gravitational acceleration is 9.81 m/s2.
Patm = 0.97 bar
m = 60 kg A = 0.04 m2
g = 9.81 m/s2
Air
(a) What is the absolute pressure (kPa) of air inside the cylinder?
Suppose that 1000 J of heat is transferred to the cylinder until the volume of air inside the cylinder doubles.
(b) Will the pressure of air inside the cylinder change? Why or Why not? (c) Will the temperature of air inside the cylinder increase, decrease, or remain the same?
Explanation / Answer
a) Pressure inside = pressure outside + pressure exerted by piston. We have the outside pressure...the piston pressure is m*g/A. (60 kg) * (9.81 m/s^2) / (.04 m^2) = 14715 Pascals 14715 + 97000 pascals = 111715 pascals b) All things remaining equal, no, the pressure will not increase. The pressure will not increase because the volume of the cylinder has increased due to the expansion of the air. Had the cylinder volume NOT increased the pressure would have increased. c) The temperature inside the cylinder will increase because the cylinder itself is heated up, and will heat up through convection and conduction.
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