# Search results

1. ### Dry ice -- How do the stores keep it from evaporating?

Ok, how do stores keep dry ice from sublimation(i think i spelled that correctly) or evaporating? Are the coolers at my local walmart some sort of special type of mechanism? thanks
2. ### High pitched noise with some elctronics

Hello:) I am working on my new 3d printer and i came accross an interesting situation. According to the manufacture, my stepper motors need to have a voltage of roughly 0.95 volts. I checked mine and they were 0.81 volts, hence the not so smooth prints. Ok, so i increased the voltage to the...
3. ### B Density and pressure -- How to calculate atmospheric pressure at higher elevations?

Ok, we all know that density is mass/volume. So if air is 1.22kg/m3,If we increase pressure, volume will change, therfore density can change. So how does one calculate density of air at higher elevations. Where i currently live, at 4700ft above sea lvl, im guessing air density is not 1.22kg/m3...
4. ### B Confused about the ideal gas law

Ok, i am struggling to figure something out. I dont know why math is so much easier than physics haha. ok, here is my struggle. I have two states, state 1 and 2, which i will call just 1 and 2. 1: T=298kelvin V=0.025m(cubed) P=310Kpa Mass1=Mass2 R=0.2870 2: T=323kelvin V=0.025m(cubed) P=...
5. ### I Specific volume and superheated gas

I was assigned an example problem today and i can do the math, look at my tables and get the right answer no problem. What i want to understand, is why when specific volume increases for r134a, that it means its supper heated? My given value for sv was .1384m3/kg which is above the .09 in the...
6. ### Converting Lbm/ft^3 to kg/m^3

1. Homework Statement The pressure drop in a duct is to be measured by a differential oil manometer. If the differential height between the two fluid columns is 5.7 inches and the density of oil is 41 lbm/ft^3, what is the pressure drop in the duct in mmHg? Report your answer to 1 decimal...
7. ### I Thermo - Difference between Potential and P/rho

Ok, im stuck on understanding when to use a part of an equation and when not to. e = (P/rho) + (Ke/m) + (Pe/m) where P is pressure, Ke and Pe are Kinetic and potential energy divided by mass. Ok, if we look at P/rho and P is defined as rho(g)(h) then the rho's divide out and we are left with...
8. ### I How are work and KE related?

Hello:) Ok, I am in my thermos class and I ran into a question about work and energy. I figured out the correct answer based off of the formula given. But what MY question is, goes back to physics 1. How are work and Ke related? IE, work is F*d and F is mg. But in Ke, I do not see the g. How...
9. ### B Finding Radius from chord length and tangent distance

Ok, i have a question. First, i am an engineering student and have done all math requirements up to linear alg. HOWEVER, my geometry is terrible, oh so terrible and i need some spoon feeding right now because i am stuck on a problem. Ok, i saw a really cool tool the other day called a radius...
10. ### B Impact force -- Airsoft versus paintball pellets

Ok, here is a small back story: I love both airsoft and paintball. Airsoft, for those who may not know what it is, is a sport where you shoot 6mm plastic bbs at each other. The bbs have differnt masses to them.. .20g, .25g .28, and .32 are common masses. When i first started last year, i was...
11. ### I Having a hard time remembering what this equation is

Ok, so it has been about 4 years since i have had physics for scientists and engineers. I am a full time mechanical and areospace student. I just started dynamics class and right off the bat, i ran into an eqution that i am not sure how to infer. It is from our rectilinear example: d^2x/dt^2 =...
12. ### I What equation is this?

So i was googling the mighty google for a general question on velocity and i happened upon this equation with no description of it. Only states it is a velocity equation velocity=sqrt((-g)(horizontal distance)/sin(2theta)) sorry, symbols is not working on me laptop at the moment Its been a...
13. ### Arc length in calc 2

Ello every one, i have interesting question. Any one who has james stewert 7th edition calc book im on secotion 8.1 studying for an exam. number 13 of 8.1 says this y= ln(secx) find arc length from 0-pi/4 here is what i do first in my opinion. y= 1/sec(sectan) y= tanx now...
14. ### Putting it all together (calc and physics)

Ello all. Ok so im excited. i am taking my first ever physics class, calc based. SO im trying to relate things from calc to physics because i am some what confused. In calc we learned that if you have P(t)= t^2 + 5t +6 this is a position function. You plug in time (t) and it will give...
15. ### Understanding charcoal

Ello all. I have a odd question but i am curious to how it relates to chemistry or better yet understand the chemistry of it. Is there a chemical equation that demonstrates the reaction a piece of wood goes threw when it is turned to carbonized wood aka charcoal. such as what elements or...
16. ### FAILED calc 2

I dont get it guys. 100% on all the quizes and homework. 42% on the final.... Deptartment policy is that you have to get a 60% or above on the final to get a D no matter what your grade is. i understand integration by parts just fine, trig sub just fine, integration with trig functions...
17. ### Positive thinking

All right guys. A lil history bout me. in high school (10 years ago) i hated math, now i like it. Never went far with it in high school. Failed trig a year and a half ago. had to retake. Now im in my first EVER calc2 class. Finished calc 1 with a high 80's (87 or so). Now im in calc2 and i...
18. ### Whats the diff between calc based and algerbra

Ok, so i just finished my first semester ever of calculus. I have never ever made it this far in math in my life period. im way excited. But im still new to calc and not sure what everything means or is. Physics 1 at my school is what they call calc based. I dont understand what they mean...
19. ### Sodium bicarb AND citric acid powder?

Ok, quick question. I know that baking soda is great for heartburn, but why is it in certain medicines, they have sodium bicarb AND citric acid powder? My wife actually uses those two compounds to make bath fizzies. She adds esentual oils to them for health benifits and smells. haha. Anyway...
20. ### Here is an excerpt i found on the web. Ernest Rutherford, born on

here is an excerpt i found on the web. Ernest Rutherford, born on New Zealand, showed in 1911 that alpha particles were sometimes very strongly scattered by the positive charges of the atom, in a way that could only be explained if such charges were concentrated in a very small volume...
21. ### This whole unit thing of mols is somewhat tricky and interesting. if

This whole unit thing of mols is somewhat tricky and interesting. if one mol of Na is 23g, then wouldnt 100.3g of NaCl be one Mol as well. I am under the impression from my lecture notes in class that the grams of a substance is the same a s a mol. I was asked a school of thought question by the...
22. ### The plum pudding question

Guys, i need some explanations please. I am in a gen chem class and have some How and why questions. Here goes..So this guy named JJ thomson had a theory he called the plum puddign theory. He says that all the electrons of an atom are surround by a positively charged sphere. Then Rutherford came...
23. ### Trig identies

1. Homework Statement Sin(2α)=-8/17 Using either double angle or half angle identities, sin,cos,tan,csc,sec and cot of alpha. 2. Homework Equations 3. The Attempt at a Solution I tried and tried BUT i am lost because in order to find cos of alpha using identies, you still...
24. ### Understqarnding equations for angular velocity

I am having dificulty understanding the equation to angular velocity. w=alpha/time so if given this statement, (this is not homework). A helicopter blade is rotating at 400 rev per minute, find angular velocity in radians per minute. So i have w=400/1 minute. great, so thats it? or is...
25. ### Dilution concepts of water

I am a mechanical engineering student who is taking his first chemistry class this upcomming semester. I have a question regarding water and its dilution principles. I have reading up on how Nuclear power plants work. I am curious to how the ocean water disolves and dilutes the radioactive...
26. ### The ionosphere

So as what i understand of this piece of our sky is that it is a bunch of ions collected together that does what? I know that we bounce radio signals off of it for HAM radios and other types of communications. I dont understand the ionosphere very much and would like to learn. What happens if it...
27. ### Just curious how electric motors work, specifically DC motors.

Just curious how electric motors work, specifically DC motors. I have some questions i would like to understand better. do the windings of a motor determine the required voltage to power it? Can a 110 volt ac motor be powered by a 12 volt dc battery with out an inverter? Can a 110 volt...
28. ### Acceleration questions

Why are there two formulas for acceleration? A=Change of velocity/time A=Force/Mass Ok, now that thats out of the way, i need some light shed on a subject. If acceleration or gravity perse is 10m/s^2, how does this relate to distance.. Meters is a distance. So if an object falls 2...
29. ### What does per second per second mean?

thrust is the ability to move a 1 pound object at 32 feet per second per second. What does per second per second mean? Does that mean for every second, the object has moved 64 feet in a given direction? if air molecules are moved at 3200 feet per second per second to deliver 100 pounds of...
30. ### Stair stepper

1. Homework Statement Build a stair climbing robot. There are no required dimensions. 2. Homework Equations MONEY 3. The Attempt at a Solution I need help brainstorming on some designs of a stair climbing robot that is cheap but yet effective. I have connections with law...