# Search results

• Users: Aki
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1. ### Finding upper and lower limits of a graph

well I just made up that graph. I can't show the data that I'm working with because it's confidential. Anyhow, there are graphs where if I apply the Chebycheff's Inequality, I get a negative value for the lower limit.
2. ### Finding upper and lower limits of a graph

Homework Statement This is not really a homework problem, but it looks like a rather easy problem that I can't quite figure out. So I have a graph like shown in the attachment: a quantity vs time graph with some data points. I had no problem finding the average, but now I want to find...
3. ### Cubic Function

Very helpful. Thanks a lot Gib Z
4. ### Cubic Function

Hey I need help with this proof: Consider the cubic function: x^3 + bx^2 + cx + d = 0 . If the two solutions of the cubic function are not equal, ie r != s, but r=-s, then prove that bc=d. Thanks
5. ### Ball vs Solenoid Valves

Yes I know how to find the Cv for a fluid: Q=Cv*root(change in pressure / specific gravity) But I do not know how to find the Cv of a gas
6. ### Ball vs Solenoid Valves

What would happen if I use a valve that has a Cv lower/larger than the one that I calculated?
7. ### Ball vs Solenoid Valves

Would stainless steel be compatible with LOX, and what using brass for kerosene? Is true that ball valves in general are bigger than solenoid valves because ball valves need an extra actuator? I've looked at the Valcor cryogenic valves, and they either have a Cv that is too small or the...
8. ### Ball vs Solenoid Valves

Thanks for your replies I'm building a LOX-Kerosene fueled rocket. I need some fuel that goes to the igniter for the first 10 seconds, and then the rest of the fuel goes to the main combustion chamber for 90seconds. The flow rates and other properties are: LOX: 1.5 L/s , -186 degree C ...
9. ### Ball vs Solenoid Valves

Hi, I want to know the difference between an actuated ball valve and a solenoid valve. Which one is more reliable? I want to program the valve so that it allows flow for 10 seconds to one outlet and after that direct the flow to the second outlet. I know I'll probably need a 3-way valve...
10. ### Hi,I need to find a suitable material for o-rings for my rocket.

Hi, I need to find a suitable material for o-rings for my rocket. It will be used in the mounting of a stainless steel combustion chamber, so I need the o-ring to be able to withstand high temperature and pressure. Any suggestions? Thanks
11. ### Spark igniter for rocket

I decided I am going to use a spark plug, and I have the Go-Ped Kicker spark plug in mind. Has anyone else used it before? http://www.msdpowersports.com/go-ped.html" [Broken]
12. ### Spark igniter for rocket

It will be 100psi
13. ### Spark igniter for rocket

Well to address everyone's concerns, this is an university student project team, and our goal is to build a reusable rocket capable of carrying a payload. We have obtained a permit from the Canadian rocketry association for launches. There are approximately 30 people working on this, and this...
14. ### Spark igniter for rocket

Okay, so I'm building a liquid propulsion rocket, about 4m tall, with a 2000lb trust. The propellants used are liquid oxygen and kerosene. Now the trouble is to find a way to ignite the fuels to start the combustion. Do you guys have any ideas? Thanks!
15. ### Finite universe

So does the shape of our universe has anything to do with the Calabi-Yau theory?
16. ### Recommend a dynamics book

Does anyone have the solution manuals to the Hibbeler textbook?
17. ### Divergent or Convergent?

Well I'm just not sure what happens when \int_{0}^{1}dx/x^{1/3} I think it converges, but I"m not too sure. because when that function is below 1/x on the graph
18. ### Divergent or Convergent?

I want to know if the integral \int_0^{\infty} dx/(4x^3 + x^(1/3)) is convergent or divergent? Thanks
19. ### Recommend a dynamics book

The Hibbeler's book is awesome. There are so many examples in there, and a tons of problems. You can pretty much learn the whole course by just looking at the examples.
20. ### Your opinion on space missions

But with current technology and the current need for space exploration, do you think that it is necessary for NASA to be spending billion dollars of tax payer's money just to send a few people up there for no incredible productive reasons?
21. ### Your opinion on space missions

Does anyone know when is the next lauch?
22. ### Your opinion on space missions

Pengwuino, I see your point. Going into space is indeed a big risk, and I'm sure most of the astronauts are willing to sacrifice themselves. But I still think that safety's first. I don't think there is much that humans can do that robots can't do. Like for repairs of satellite, the...
23. ### Your opinion on space missions

I'm writing a research paper for my english course, and I've decided to do my paper on whether or not we should replace all human space missions with unmanned missions. What are your opinions on this matter? And do you know where I can find some articles on this topic? Thanks
24. ### Airbags for rockets

I know that airbags isn't the best option, because you never know where the rocket will land and they can only deflate once. Are there any options for protecting the rocket during landing other than airbags?
25. ### Airbags for rockets

Hi, I'm building a rocket, and my team is planning to use airbags to protect the tanks from crushing during landing. I'm a newbie at this, and I want to know where I should start:) Thanks
26. ### Forced Oscillations frequency

I'm doing this problem from Mastering Physics, and I'm really stuck on this problem Assume that, when we walk, in addition to a fluctuating vertical force, we exert a periodic lateral force of amplitude 25 N at a frequency of about 1 Hz. Given that the mass of the bridge is about 2000 kg...
27. ### Measuring Temperature using wavelenghts

I want to know the formula to find the temperature of outer space by measuring the wavelenghts of the electromagnetic radiation coming from that area. Does anyone know what I'm talking about?
28. ### Programs Physics Major

Thanks you for all the advices. I think I'm going to try engineering the first year and see how I like it. If I don't, then I'm going to major in theoretical physics. If I don't try engineering, then I'll never know what it's like, especially since I've always thought I was going to be an...
29. ### Programs Physics Major

I"m in grade 12 now, and I'll be going to university next year. I got accepted to Engineering, but now I'm not sure if that's what I really want to do. I love theoretical physics, and I don't mind majoring in that, except I'm not sure what are some career options. I don't like lecturing...
30. ### Integrating to find the volume

x=r \cos \theta , \sqrt {r^2 - x^2} = r \sin \theta , dx = -r \sin \theta d\theta
31. ### Integrating to find the volume

Help, I'm trying to find the hypervolume of a hypersphere and I'm stuck on this: V^4= 2(\frac{4\pi} {3}) \int_0^r (\sqrt{r^2-x^2}) ^3 dx I don't know how to do the integration, and I can't expand the (\sqrt{r^2-x^2}) ^3 The answer should be \frac{\pi ^2}{2}r^4 Please help, thanks
32. ### Melting of ice

When a figure skater pulls her arms in while she's spinning, it causes her to spin even faster, right?
33. ### Melting of ice

Thanks xanthym for the good explanation, however, I still have a question about the first question. If the polar ices are melting, then wouldn't that cause the Earth to have a smaller "radius" (from the center of the Earth to the top of the polar ices)? Just like how a figure skater spins...
34. ### Are black holes black afterall?

so if there was enough of those particles radiating out, eventually the black hole's mass would become zero?
35. ### Dark matter particles

WIMPs are really hard to detect because first like the name tells us, their interactions with "normal matter" is weak. Also billions of those are passing through the Earth, and even our bodies every second, and yet they don't leave a trace.
36. ### Are black holes black afterall?

so Hawking radiation is basically composed of the particles that fell into the black hole?
37. ### Are black holes black afterall?

Are black holes black afterall? I remember reading in Hawking's book that black holes aren't black.

g=9.8m/s^2
39. ### Gravity - Electric Force questions

Gravity can actually be repulsive. Gravity doesn't just depend on mass and distance, but it also depends on pressure. If the pressure is negative, then gravity then becomes repulsive, and that's basically what contributed to the early expansion of our universe according to the inflation...
40. ### Melting of ice

Question #1: If all of Earth's polar ice were suddenly to melt into the oceans, in the short term the length of the day would a) increase b) remain the same c) decrease d)first decrease, then increase The answer is a) , but why? Question #2: An ice cube of pure fresh water...
41. ### Aerospace vs Aeronautical Engineering

Aerospace Engineering
42. ### Aerospace vs Aeronautical Engineering

in Canada they also have AE at U of Toronto
43. ### A question about dimension

there are infinite squares in a cube. so to draw a conclusion: there are infinite cubes in a hypercube.
44. ### Volumes in the 4th spatial dimension

I'm already lost here, lol. How did you get 4*pi when you integrate 2*pi*sin(r)? Shouldn't it be 2*pi*(-cos r) if you take the antiderivative? And what do you mean by "integrate between 0 and pi)? Thanks
45. ### Marks/Symbols at the end of solutions

QED also means Quantum Electrodynamics :) Something that Feynman developped
46. ### Problem on finding the second derivative.

it would be easier if you rewrite the original equation like this: x(x^2 -4)^-1. So you don't need to deal with fractions
47. ### Volumes in the 4th spatial dimension

How would you calculate the volume of a 4-dimensional object? Like a hypercube, hypersphere, etc...
48. ### Help with air pressure

I'm building a hovercraft, and I am using an old computer fan to blow air into a plastic garbage bag and fill it up. I need to poke a few holes on the bottom of the garbage bag to let the air out, and I want to have a less friction as possible. What size should the holes be? And how many?
49. ### Derivative of e^x

wow Physicsguru, thank you, I'm sure you put lots of time in answering my question. Thanks
50. ### NASA The probability of working for NASA

Which probability is greater? becoming a professional athlete? or working for NASA?