Pistons, Pressure, Work, and Height

In summary, the conversation discusses finding the piston height of a circular container with a lead piston floating on compressed air. The question asks for the height at a specific temperature, as well as the work done by various forces on the piston. The conversation includes a solution attempt and a discussion of finding the correct answer.
  • #1
Phoenixtears
83
0
SOLVED

1. Homework Statement


A circular disc of lead has a mass 50 kg, it acts as the piston of a circular container shown in Figure CP16.69. The disc floats on 0.140 mol of compressed air. (Image Attached)

Figure CP16.69

(a) What is the piston height h if the temperature is 30°C?
cm

(b) How far does the piston move if the temperature is increased by 105°C?
cm

The following questions involve work, recall conditions for (-) work and (+) work ...
(c) How much work did the atmosphere do on the piston?
Nm

(d) How much work did the gravity field do on the lead piston
Nm

(e) How much work did the gas do on the lead piston?
Nm


Homework Equations



P= F/A
PV=nRT

The Attempt at a Solution



I haven't tried anything but A- I'm stuck on that one.

I first found the pressure using P=F/a. I found the weight by doing 50*9.8m/s2 and then divided by (pi)*r^2. That answer, which is already in Pa, I then added to 101,300 pa, the atmospheric constant for pressure. That pressure I used in PV= nRT to find volume. Then I used the volume of a cylinder formula (V= (pi)*r^2*h) to find height. This answer did not come out right (and I made sure to be in centimeters). Does anyone know where I'm going wrong?

Thanks in advance!

~Phoenix
 

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  • #2
Phoenixtears said:

Homework Statement



A circular disc of lead has a mass 50 kg, it acts as the piston of a circular container shown in Figure CP16.69. The disc floats on 0.140 mol of compressed air. (Image Attached)

Figure CP16.69

(a) What is the piston height h if the temperature is 30°C?
cm

...

I first found the pressure using P=F/a. I found the weight by doing 50*9.8m/s2 and then divided by (pi)*r^2. That answer, which is already in Pa, I then added to 101,300 pa, the atmospheric constant for pressure. That pressure I used in PV= nRT to find volume. Then I used the volume of a cylinder formula (V= (pi)*r^2*h) to find height. This answer did not come out right (and I made sure to be in centimeters). Does anyone know where I'm going wrong?
Your approach is correct. If you give us all the information we will be able to check it. We need the radius of the cylinder. Then show us your work. I am not sure why you are working in centimeters. You should be working in MKS.

AM
 
  • #3
Thanks! I figured out what was going wrong. I had kept my answer in meters instead of centimeters. It's so frustrating when that happens.

Thanks again!
 

1. What is a piston?

A piston is a component of an engine or pump that moves back and forth within a cylinder to transfer energy from expanding gases or fluids into mechanical work.

2. How does pressure affect pistons?

Pressure is the force per unit area acting on a surface. In the case of a piston, pressure is responsible for pushing the piston downward, converting the potential energy of expanding gases into mechanical work.

3. What is the relationship between work and pistons?

Work is the transfer of energy from one system to another. In the case of pistons, work is done when the piston moves back and forth, converting energy from expanding gases into mechanical work.

4. How does height affect pistons?

Height can affect pistons in different ways, depending on the specific application. For example, in a hydraulic system, the height of the piston can determine the amount of pressure and force exerted on the fluid. In an engine, the height of the piston can affect the compression ratio and overall performance.

5. What factors determine the efficiency of pistons?

The efficiency of pistons is determined by various factors such as the design and materials used, the pressure and temperature of the system, and the friction between the piston and cylinder walls. Proper maintenance and lubrication can also impact the efficiency of pistons.

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