# Search results

1. ### B How to set up an integral to integrate over a sine wave?

How do I setup an integral to integrate over the following equation: V(t) = 1/(R*C) integral to t Vin(t) dt This is the capacitor voltage over time formula. I want to integrate over a sine wave from 9 to 81 degrees. Frequency of 120Hz, amplitude of 120V. The formula I used in wolframalpha is...
2. ### B How to distribute a fraction?

I'm given the problem 14x+5y=31, 2x-3y=-29 This is a set of linear equations that I am asked to solve. That being said I am getting hung up on how to distribute a fraction. The answer is x=9, however, I am getting x=36 and the step I do not understand is distributing the fraction. We then get...
3. ### Calculating Free Body Diagram Forces

On EngineersEdge.com they have a free body diagram of a scissor lift https://www.engineersedge.com/mechanics_machines/scissor-lift.htm Can anyone explain how the Fy, Fx components are determined? What is specifically confusing to me is how Fy is opposite in direction given the system. To me...
4. ### MeOH:H2O Freezing Point Depression Calculation Issue

I noticed that my windshield washer fluid has methanol in it to reduce the temperature of which it freezes. I know it freezes at approximately -28°C which gives us a concentration of MeOH at approximately ~30% by weight. However, when I try to calculate the required methanol using the mSolute...
5. ### Looking for info on balancing and counterbalancing design.

I wasn't quite sure which section to post this in but engineering was the closest to my application, although this could be a basic physics question. I'm not sure. I want to learn how to design a counterbalance such as that in an engine crankshaft. This mechanism has been of interest to me...
6. ### Can someone explain this complex math problem?

I'm working out an impedance matching problem from a textbook (it is not part of any coursework) and I am trying to figure out how they get the 315 term in the polar coordinates below. Z = (XC*RL)/(XC+RL) = (-j333*(1000))/(-j333+1000) = 315 , -71.58* = 100 -j300 ohms I calculated that...
7. ### I What is the approximate impedance of an RF plasma "antenna"?

I've searched high and low for data regarding this from scientific papers to books and I cannot find anything in regards to the approximate impedance to excite a vacuum vessel to plasma state. In particular I want to built a RF Plasma cleaning chamber, however, I am not sure how to design the...
8. ### How do I get a DC difference amplifier working?

I've been trying to figure out why my DC subtraction amplifier is not working, and am completely baffled. I have set up an op amp with no feedback resistors with voltages applied to both the inverting and non-inverting inputs as specified below. I previously had the op amp setup with a 10x gain...
9. ### Calculating required amount of molecular sieves for PSA?

Does anyone know how to properly calculate the amount of molecular sieves needed for a pressure swing adsorption system? I have searched application notes, books, and of course google, and while I find the basics of how they are constructed I cannot find any information on the quantity...
10. ### Calcium Carbonate -> Calcium Oxide, but only getting Hydroxide. Ideas?

I was trying to calcine some CaCO3 (Calcium Carbonate), but ended up with Calcium Hydroxide. To test if I had Calcium Carbonate I added it to some vinegar, no gas was produced. I then mixed in a small amount of the powder with a large amount of water and passed CO2 through it, and it became a...
11. ### Calculating Insulation Thickness

I'm trying to calculate insulation thickness for a foundry, and can't figure it out after spending a few hours searching. Refractory: Kast-O-Lite Material Required: 1.44g/cm^3 Thermal Conductivity: 0.65 W/m*C Maximum inside temperature is 1648*C I figured there would be a minimum of...
12. ### Amount of Propane Required to Melt 1L Aluminum

I started off yesterday learning about specific heats, and measuring my ice cubes to figure out the correct number to cool my tea to a proper drinking temperature. Now today I was curious how much propane would be required to melt 1L of Aluminum since I'm also interested in casting Aluminum...
13. ### Confused with Rate Problems/Coefficient, Pos/Neg signs.

How do I determine if I subtract or add the coefficient to the fraction? ex. 1-(-48/18)*Sh=384 vs 1+(-48/18)*Sh=384? Also, It would be the Sh+Sm=312 where I get the coefficient "from" right, specifically the second "Sh" term where as the sm term is eliminated with -sm. Thanks! (The...
14. ### AM Demodulator: SSB -> AM; Op Amp?

Greetings Physics Forums, I'm reading up on Radio Circuits and studying for my General's Amateur Radio License and was learning about AM Demodulators. I understand that in AM you can use a peak detector to get the modulated audio out however in SSB radio don't you have to double the...
15. ### Calculators HP50G, Number solver menu no longer shows

Hey PhysicsForum, When I press Right Shift + 7 (NUM.SLV) For solving linear equations i usually get the menu but now it shows a different menu instead of the popup menu it now shows Root Diffe Poly Sys and Tvm over the F keys. Can anyone enlighten me as to how to get my menu back? Thanks...
16. ### Driving 15 LCD Possible?

Driving 15" LCD Possible? Hey Physics Forum, I have some large LCD's such as those out of laptops and I was wondering if they can be turned into a monitor for a computer or something such as a project screen. I'm not so much looking for a step-by-step or any instructions because I'm not that...