# Search results

1. ### IPhone on space.

http://www.wired.com/wiredscience/2011/06/iphone-space-shuttle/" [Broken]. Anyways, it says that it will look for radiation effects with "single bit upsets", is memory really that sensible to radiation?
2. ### Photons reflecting off mirrors, wheres the flaw?

Hello. Consider 2 spacecraft isolated in space, with a mirror on their back, facing each other. One light pulse is shot between them. The photons reflect off the first one, transferring a momentum off 2p, travels in the opposite directions, reflects off the second spacecraft, giving it 2p...
3. ### Double derivative proof

1. Homework Statement \sqrt{x}+\sqrt{y}= 4 prove that y''=\frac{2}{x\sqrt{x}} 3. The Attempt at a Solution \frac{dy}{dx}=-\frac{\sqrt{y}}{\sqrt{x}} I tried solving for the second derivative and got \frac{d^2y}{dx^2}=-\frac{-x\frac{dy}{dx}-y}{2\sqrt{\frac{y}{x}}x^2} [ Which is...
4. ### Superior implicit differentiation, prove answer.

1. Homework Statement 2XY = Y^2 prove that y''2 = \frac{y^{2}-2xy}{(y-x)^3} EDIT: Sorry, don't know how to insert a space in Latex. 2. Homework Equations 3. The Attempt at a Solution 2y+2x \frac{dy}{dx} = 2y \frac{dy}{dx} \frac{dy}{dx}(2y-2x) = 2y \frac{dy}{dx}= \frac{y}{y-x}...
5. ### Physics of Myelin

This post might be in the wrong subforum, I wasn't sure where to put it, sorry. Quoting another website: For me this two paragraphs contradict. The first saying that the myelin increase the speed of the impulses, and the second says that "myelination helps prevent the electrical current...
6. ### Another derivative confirmation.

1. Homework Statement Find the derivative of: f(x)= ((x+xsinx)/(1+2tan2x))3 3. The Attempt at a Solution I solved it and got : f'(x)= (3(1+2tan2x)3(x+xsinx)2(sinx+xcosx+1)-12(x+xsinx)3(2tan2x+1)2(tanxsec2x))/(1+2tan2x)6 Can anyone confirm if this is alright? Also, anyone...
7. ### Derivative confirmation

1. Homework Statement Derive the following: f(x)= (2+3sinx)(4+5cosx)tanx 2. The attempt at a solution I derive it and got f'(x)=(4+5)tanx(3cosx)+(2+3sinx)(tanx(-5sinx)+sec2x(4+5cosx)) Can someone confirm if this is right?
8. ### When theres only brute force left

What a stressful evening. I figured I wanted to do a pretty complex valve system just to learn a bit, using solenoids valves and microcontrollers to have everything computarized. To save a few bucks I thought making my own solenoids using magnet wire from my motor junkbox. Oh boy... over half...
9. ### The real cause of refraction.

Hello, while making my tea and watching the spoon inside the glass (with water), I start questioning myself what really is refraction. On class they just told me refraction is because light goes slower in a medium, so it bends according to Snell's Law. What is Snell's Law? Light bends to a...
10. ### Isolated Ground

I've seen many 'isolated ground' outlet, in schools and hospital. Tried to google it but didn't find much information about those. They're and orange case, and usually are just beside the normal mains. What is special about those? Are they safer? Thanks, Sakha.
11. ### Happy New Year!

Tonight is Rosh Hashana (Jewish new years) and I want to wish you all Shana Tova uMetuka (a sweet and good year)!
12. ### Power limit on mains.

Hi. Sometimes it happens that if you have a lightbulb and something else that is rated high wattage in the same mains outlet (sometimes even on different outlets), and turn the high-wattage appliance, you can see how the lightbulb gets dimmer. Why does this happens? Thanks.
13. ### Negative wire when jumping start a car

Hello, I've always heard that when you will jump start a car you connect both cathodes (positive terminal) and you connect the anode of the good battery to the chassis of the stranded car. Why is the setup like this and not connect both negatives with each other too?
14. ### Ants inmune to microwave.

I've read many stories of ants being inmune to microwave, and also of coakroches being very resistive to X-rays and heavy radiation. My first thought was that ants have little water content, but that doesnt sound right because most animal have plenty of water. So instead I maybe wondered that...
15. ### Doors, windows, pressure.

Hello, sorry for the weird title, I couldn't think of something appropriate enough. There is a window in my bathroom, about 1 meter from the door, its a pretty big window. Usually I maintain it close because I hate noise. Today I just felt like opening it and noticed something strange...
16. ### Silver-Silver Electroplating

Hello, I want to electroplate silver stuff with more silver to remove the tarnish, its mainly an experiment I want to do because its always easier with Twinkle tarnish remover. It's possible to do this with Silver Cyanide in a nitric acid solution? If yes, what should be the pH? Or should I...
17. ### Form of energy released by fission bombs

Atomic bombs are really powerful and destructive devices. I understand that during a fission reaction, the parent isotope splits in 2 lower mass isotopes with high kinetic energies due to the binding energy that were released. But I dont understand how this becomes into the destructive effects...
18. ### Heat transfer in space

Hello. People always say that the space is 'cold', and I've always heared that on a satellite, the side facing the sun is really hot, while the dark side is very cold. What I dont understand is how can the dark side be cold if the heat it had couldnt escape in any way except radiation, which, to...
19. ### Height affecting wireless signal

Hello. I went to get a new router because I finally decided to get wireless. I got a Linksys WRT120N which supposedly has a decent range, according to the sellsman. On my apartment the router is about ten meters and has a couple walls between it and the computer. The computer receives really...
20. ### Young's Modulus and volume

After a tough discussion with my friends, I opt to ask here because we aren't coming to an answer. When stress is applied to a solid, lets say an iron rod, will the volume change, or when the length of the rod shrinks or stretches, the area of the cross sectional area will reduce or increase to...
21. ### Not electrocuted?

Today, a friend was moving a cable with a little piece of metal. He happened to cause a short circuit and nothing happened to him. The circuit was holding around 10 white lamps, 120V and I can guess its about 40W each. The little piece of metal even got perforated, and yet nothing happened to...
22. ### Air and Earth's rotation

Hello. We all know that at the equator the Earth's rotates at over 1000 mph. My question is why don't we feel the air of the atmosphere "crashing" with us. What holds the air so that it keeps moving with us?
23. ### Thrust sources

I was reading about a few mission that sent spacecrafts very far from the Earth. Like the Pioneer 10, which went past the asteroid belt, Jupiter, and lost contact with Earth on 2003. I tried to search for, but didn't find what those kind of spacecrafts use to gain speed in the space. I know...
24. ### Why CPU prices so high?

The other day, watching to buy a new computer I saw CPU prices, and I asked myself why prices are so high. I mean, its just a tiny piece of semiconductor. Does the high price comes from the design of them, or it's that manufacturing them are expensive and machines to work at such small...
25. ### Educative physics game.

Hello. I'm entering to a software competition and I need to create an educative game, so I want to make it with physics. Anyone have an idea, suggestion or anything on what kind of game I could make. Thanks in advance P.S: I'm in 11th and the game is made with Visual Basic
26. ### AP books

I'm taking the AP class on calculus AB, and I want to order a book. Anyone would recommend one? I think the Princeton Review is the best one, but the Kaplan's and Barron's seems good too, so any opinion would help. Also I'm taking AP macroeconomics. I know this is not a a topic that people...
27. ### Cars persecution

1. Homework Statement A thief steals a car in front of two cops, A and B. The thief's initial velocity is 25m/s, cop A starts his car with 3m/s2, and cop B starts 10 seconds after cop A, but with 5m/s2. After 200m from his initial point, the thief notices the cops and start accelerating at...
28. ### Amplitude-frequency relationship

Hello. I was doing a chemistry test, one question was asking to state the relationship between the amplitude and frequency of a wave. I wrote that they had no relationship, as amplitude can go higher with frequency staying the same. Was I right?
29. ### Proton mass-energy

After some learning on atomic physics, I came with the following question. Proton mass is 1.67262158 × 10E-27 kilograms, and its velocity is proportional to its energy. So then, in E=mc^2, you only plug the m, and you will always get the same value. I don't quite understand that a proton...