1. ### Why are two pieces of wood stronger when bound together?

The answer learned in class is that the two 2*4s are able to distribute the load over both of them, but I don't think this is an actual answer because that's balanced by the fact that each block is half the area. Does anyone know of the reason for this observation? Thanks!
2. ### Maximum compression of a spring?

I found the amplitude of the simple harmonic motion that results (0.367, and I know this is correct because I entered it and it was marked as a correct answer), and assumed it would be the same value for the maximum compression since x(t) = Acos(wt). And, since the maximum value of cosine is 1...

Hi! I recently noticed that posted images can lose quality when they are copied from a thread to a new thread. It seems they undergo some extra compression, and I don't understand why. Compare for instance the photos in this PF photo contest thread with the photos in the corresponding vote...
4. ### Compression of human bone: forces

Homework Statement While unrealistic, we will examine the forces on a leg when one falls from a height by approximating the leg as a uniform cylinder of bone with a diameter of 2.3 cm and ignoring any shear forces. Human bone can be compressed with approximately 1.7 × 10^8 N/m2 before...
5. ### I Reversible compression of a gas - faulty reasoning?

Hello, I am trying to figure out where my reasoning falls apart in this thought experiment: To determine if a process "A" is reversible (or at the very least internally reversible), I try to picture a reversible process "B" that involves only heat transfer and links the same two endpoints that...
6. ### A The exact formula for PV-work in an irreversible process

I've written a short text adapted from a previous post by Count Iblis. I'll append it below. It shows that irreversible PV-work is always smaller than reversible, which fits very nicely with W = Pext ΔV. I'd be interested if there's a way to show that W is exactly equal to Pext ΔV for all...
7. ### How does compression cool water in a household water cooler?

How does compression cool water in a household water cooler? I was reading and it says, " The water inside the water cooler is fed into a reservoir, where it is cooled using a refrigerant. A refrigerant is a cooling medium that is circulated in pipes that are located close to the reservoir in...
8. ### Gas Turbine Performance

Hey Mech Eng Forum, I'm currently examining the performance on gas turbine and wondering: How is the performance of gas turbines (Primarily thermal efficiency and net-work output) influenced by the pressure ratio and temperature constraints? Additionally, what is the benefit of 2 stage...
9. ### Calculation of heat created during compression

Homework Statement Hello, I have a task to make a heat balance of the evaporator. To do this, I was told to carry a few smaller energy balances in different parts of the evaporator. One of the things I had to calculate was the heat generated during steam compression. -steam is entering...
10. ### Compression/Tension in Steel I Beams

Homework Statement Why is a steel beam shaped in the form of the letter "I" still strong enough to bear a load? 1) Its compression area is located on the top of the I beam. 2) Its tension area is located on the top of the I beam. 3) Its neutral area is located on the top of the I beam. 4) Its...
11. ### Thermodynamics: Compression of an Adiabatic Gas

Homework Statement Assume 1.500 mol of a monatomic ideal gas is compressed from 3.00 L to 1.00 L. a. If the initial and final temperature is 10.0 °C, what are the initial and final pressures (in atm)? b. How much work input (in kJ) is required if a reversible isothermal path at 10.0 °C is...
12. ### How to analyze the compression of a clay ball

Hello all! This is my first post on the forum. As some background, this issue pertains to the IB Physics Internal Assessment that I am in the process of writing. Thanks in advance for your help! Homework Statement My research question is: How does the drop height of a consistent-size clay ball...
13. ### How to calculate stress on a pipe wall

I have a PVC fitting that keeps cracking. The fitting consists of 2 parts. One piece is placed over the end of a flexible PVC ribbed hose, and the other is inserted inside the hose. The 2 parts act as a compression fitting to attach to the end of the hose. The hose typically has an outside...
14. ### I Leverage and Forces on a Pivot System

The diagram drawn below shows a lever system fixed to a point on the left with a pivot point (circle) on the line which attaches to vertical line. I have dimensions for Y and Z and the forces pulling the lever down on the right, and the force acting upwards from below. I am trying to work out...
15. ### Energy cost of intercooling

Hi all, I am looking at a air compressor train design which looks like this: I know how to work the compressor work needed for a two stage compressor, and hence how much work I can save using 2 instead of 1 stage. The question I have is: How much energy does it require to operate an...
16. ### Traction/ Compression stress and strain exercise

Hello everyone, could you help me with this exercise? I am stuck, and I can't find anything on the internet that solves this. Your help is very much appreciated :) 1. Homework Statement Circular steel bar, clamped at extremities. Two parts: A(ab)=800mm² A(bc)=400mm² L(ab)=...
17. ### Conformability elastic material compressed on a wavy surface

Hey there, I'm struggling in finding the useful equations to determine some conformability parameters for a finite elastic material (EPDM) compressed on a rigid slightly wavy surface. I would like to optimize the thickness of the elastic material in terms of indentation depth and thus contact...
18. ### I Heating upon sudden elastic compression of material

Hello, I would expect the heating of an elastic material upon sudden elastic compression to be given simply by the first law of thermodynamics, i.e. Delta Q=Delta U + P Delta V where P is constant since the compression is applied suddenly as in a square-wave pressure pulse (this is equivalent...
19. ### Helium for flying-Buoyancy

Hello everyone, Following Buoyancy formula, how much helium is required to help someone with 80 kg weight against gravity? While the Buoyancy depends on volume, what happens if we compress helium? Thank you in advance. Regards, Behrouz
20. ### Tensile and compressive forces

Example of a tightrope walker: Now, the weight force acts at a point. The rope is stretched. Compressive forces act inwards towards that point (opposite to TL and TR, the tensile forces). The resultant of the compressive forces equals the weight and is in the same direction – the weight force...
21. ### High velocity impact testing

Hi all, I am doing a High Velocity Impact testing using a gas gun I have to figure out a) is my test running well and I am not getting any reflection? Please correct me or help in calculating if I am wrong at any point. I guess, I can figure out by calculating the time required for the...
22. ### Can I elevate a bed by 4 inches with PVC and sleep on it?

Hi everyone, it's my first post! I need to elevate a bed by 4 inches for a while. I did some work on this problem already. Here's all the information I used to reach my conclusion: expected total weight with mattress and occupants = 220.92200 kilograms bed weight = 54 kg = 54,000 grams =...
23. ### Compressible fluid other than air.

Hello Is there any fluid other than air which is compressible. http://www.scienceinfusion.com/air-the-fluid/
24. ### Confused - Pressure in a canister?

A manufacturer quotes a standard co2 canister contains 16g of co2 at a volume of 20cm^3. So I need to calculate the pressure in the canister.... Using ideal gas law P = nRT/V n = 0.364mol (16 of co2) R = 8.314 J/Kmol (universal gas constant) T = 294k (gas is at room temp 21 deg C) V =...
25. ### Compression of pure nitrogen: Calculating power and temperature

I am trying to find the theoretical power required to compress nitrogen from a pressure P1 to P2, as well as the final temperature T2 after compression. I found no formula that were anywhere near complete, but I found this tool, which tells me that from 300K@1Bar, I need 271.4kw (271kj/s) to...
26. ### Gas Compressor

Dear All, I am a mechanical engineer who has recently started working in the oil& gas industry (compression). I would appreciate if someone can guide me to where can I learn about reciprocating compressors. Much appreciated.
27. ### The coefficient of friction by spring compression

Homework Statement A box has the mas 50.0Kg. The box slides on a horizontal surface that has friction. The box has the velocity 3.00m/s when its 0.600m away from a spring with negligible mass and the force coefficent 20Kn/m. The box hits the spring and comes to a momentary rest after...
28. ### Design of Vapour Compression Refrigeration Cycle

Hi! For our class project, we have to design a system that freezes an amount of water as quick as possible. The refrigerant is R134a. The compressor is known. I don't really know how to get started here. How do I choose the evaporator pressure and the superheating, and equally the condensor...
29. ### Convergent Subsonic Ramjet Utilizing Shockwave Compression

Hi, I am working on investigating an idea I proposed regarding a ramjet that operates in subsonic flow (of a fixed speed) with a convergent intake. That utilizes the pressure immediately behind a standing shock-wave for compression. I have posted a link to my initial report here and I now need...
30. ### Coining/axially-symmetric compression

Homework Statement You are asked to figure out the force required to coin a 25-cent piece and are given the final dimensions and an average flow stress. Sticking friction is "reasonable" Hosford and Caddell 2nd Ed. Q 7-3 Homework Equations Pa = Y + 2kR0/3h0 The Attempt at a Solution I...