ME 302 Homework 4
Due In Class Monday Feb. 14
When solving the following problems.
You MUST start with the generic First Law and Conservation of
Mass, cross out terms based on your assumptions, and integrate as discussed and shown in class.
1)
Given a temperature of
and
, use the compressibility factor and the
chart on back of the tables that were handed out to show that the ideal gas assumption is not
very good for water, but is alright for Nitrogen.
2)
Use the First Law of Thermodynamics to show that a polytropic process in a closed cylinder for
an ideal gas (with gas constant
) is adiabatic if
, where
is the polytropic exponent and
is the ratio of specific heats.
You may assume that
is constant.
Hint: This problem is more
direct if boundary work is calculated with mass and temperature rather than pressure and
volume.
3)
An air gun, shown below, contains a mass of air in a cylinder with a crosssectional area
.
The
bullet has mass
and expansion of the highpressure ideal gas undergoes a polytropic process
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 Spring '11
 helum
 Thermodynamics, First Law Of Thermodynamics, Heat, Bullet

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