Compressed air lift question (thermodynamics)

In summary: So, in summary, the platform is initially at a height of 0.5m, and it is initially balanced by normal force given by f=-mg. After the 50kg mass is moved off of the platform, the platform's new position is 0.75m and its maximum velocity is V_max=3.5m/s.
  • #1
hahaha158
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0

Homework Statement


A platform is supported on a piston by compressed air in a cylinder.
The mass of the platform and equipment being lifted is 1100kg. The pressure needed to
support this mass is 800kPa, and it rests initially at a height of 0.5m. The pressure supply
is closed so that no gas enters or leaves the cylinder. One of the pieces of equipment with a
mass of 50kg is moved o the platform. The entire system is at room temperature (300K)
(a) What is the new position of the platform? (b) What is its maximum velocity?


Homework Equations



W=PdV
PV=nRT


The Attempt at a Solution



I'm having trouble trying to find an equation that relates mass and height, that can also be related to pressure. There is no radius given, so I do not know how to find the volume of the ccylinder. Also, I am wondering what "no gas enters or leaves the cylinder" means in terms of pressure/temperature etc.
 
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  • #2
Consider a force balance on the piston. The weight of the piston, [itex]mg[/itex], is balanced by what force?
 
  • #3
Undoubtedly0 said:
Consider a force balance on the piston. The weight of the piston, [itex]mg[/itex], is balanced by what force?

It would be balanced by normal force given by f=-mg?

I can use this to calculate the area using P=F/A which is constant.

Given this I can find P when the 50kg mass is removed.

But how do I relate this to the height?
 
  • #4
hahaha158 said:
It would be balanced by normal force given by f=-mg?

I can use this to calculate the area using P=F/A which is constant.

You are close. What you call a "normal force" is actually the force due to pressure, [itex]F_P = PA[/itex] (where [itex]P=800\,\mathrm{kPa}[/itex]). It is this force that balances the weight of the piston. In other words, this relationship allows you to find the area of the piston, and hence the initial volume of the cylinder.
 
  • #5
I am butting in just to track this thread.
 

1. How does a compressed air lift work?

A compressed air lift works by using the principles of thermodynamics to convert potential energy into kinetic energy. Compressed air is forced into a chamber, creating pressure that is used to lift an object. This pressure is released through a nozzle, creating a high-speed jet of air that lifts the object.

2. What is the efficiency of a compressed air lift?

The efficiency of a compressed air lift can vary depending on factors such as the design and size of the lift, as well as the pressure and volume of the compressed air. Generally, compressed air lifts have an efficiency of around 60-70%, meaning that 60-70% of the energy put into the system is converted into lifting force.

3. How much weight can a compressed air lift lift?

The weight that a compressed air lift can lift depends on the amount of pressure and volume of compressed air being used. Generally, a compressed air lift can lift objects that weigh several hundred kilograms. However, the design and size of the lift can also affect the weight capacity.

4. What are the advantages of using a compressed air lift?

Compressed air lifts have several advantages, including low cost, simplicity in design, and the ability to lift heavy objects without the need for complex machinery. They also have the ability to operate in hazardous environments, such as underwater or in areas with explosive gases.

5. What are the potential dangers of using a compressed air lift?

The main danger of using a compressed air lift is the potential for high pressure and high-speed air jets to cause injury. It is important to follow safety precautions and use proper protective gear when operating a compressed air lift. There is also a risk of equipment failure or malfunction, so regular maintenance and proper training are necessary to ensure safe operation.

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Thank you for your response AM. I appreciate it and will work through the steps.
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