AP Physics Thermodynamics Homework

In summary: So 295°F = 754.67 deg. R and 180°F = 639.67 deg. RBut the calculation is correct, except that you should express the efficiency as a percentage, not a decimal fraction.
  • #1

Homework Statement

1)The pressure on an ideal gas is cut in half,
resulting in a decrease in temperature to
0.604038 of the original value and a change
in the volume.
Calculate the ratio of the final volume to
the original volume of the gas.

2) Steam moves into the cylinder of a steam
engine at a constant pressure of 2.6 × 105 Pa.
The diameter of the piston is 25.6 cm, and the
piston travels 31.3 cm in one stroke.
How much work is done during one stroke?
Answer in units of J

3)A steam engine has a boiler that operates at
295◦F , with a temperature of 180◦F.
Find the maximum efficiency of this engine

Homework Equations

1) This problem I am not sure

2)Same thing. I have 40 problems and I am posting the few I don't get. maybe (Qin = Wout + Delta U)

The Attempt at a Solution

1) No idea how to attempt.

2)No idea. 3)
295F = 146.11 C + 273= 419.11
180 F = 82.22 C + 273= 355.22

355.22/419.11 = .84755
(1 - .84755) = .1524 = 15.24%
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  • #2
For the first one, since the process is not specified, try using Ideal gas equation.
For the second, since the process is isobaric use the formula of work done during the process.
The attempt for the third question is correct.
  • #3
You should recognize that degrees Rankine is the absolute temperature scale using Fahrenheit degrees:

deg. R = deg. F + 459.67

1. What is thermodynamics?

Thermodynamics is the branch of physics that deals with the study of heat and its relation to energy and work. It also includes the study of how energy is converted and transferred between different forms.

2. What are the laws of thermodynamics?

The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or converted. The second law states that the total entropy of a closed system will never decrease over time. The third law states that the entropy of a perfect crystal at absolute zero temperature is zero.

3. How do I solve problems involving thermodynamics?

In order to solve problems involving thermodynamics, you must first identify the system and its surroundings, and then apply the laws of thermodynamics to the system. It is important to properly define and calculate the variables involved, such as temperature, heat, and work.

4. What is the difference between heat and temperature?

Heat is the transfer of thermal energy between two objects due to a temperature difference, while temperature is a measure of the average kinetic energy of particles in a substance. Heat is measured in joules (J) and temperature is measured in degrees Celsius (°C) or Kelvin (K).

5. How does thermodynamics relate to real-world applications?

Thermodynamics has numerous real-world applications, including refrigeration and air conditioning systems, power plants, engines, and chemical reactions. It also plays a crucial role in understanding weather patterns and climate change. Understanding thermodynamics can help us make more efficient and sustainable use of energy.

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