Science & Mathematics - 27 October 2007

As stated above. I'm a student doing IB so please explain using not too hard terms.

Thank you for your help!

2007-10-27 16:51:53 · 3 answers · asked by danielcatherinehk 2 in Biology

Help please! What are the partial derivatives of the following:
a. -2xy/((x^2+y^2)^2) with respect to x
b. (1-((x^2-y^2)/(x^2+y^2)^2) with respect to y

2007-10-27 16:49:39 · 2 answers · asked by kmf12 1 in Mathematics

2007-10-27 16:47:59 · 9 answers · asked by Denise J 1 in Weather

A 12v DC power supply from a 500 Watt power supply unit is being used to heat a wire of approx 1 meter. As I understand if more current passes through the wire, the hotter it gets. In order to vary the heat of the wire I need to vary something.

My question is...

What is that something and which way is it to be varied (as in up or down)?

Also what would I need to do it ?

Many thanks,

Paul

2007-10-27 16:43:15 · 5 answers · asked by Don Pav 1 in Engineering

Its

Write the mixed number as an improper fraction, or write the improper fraction as a mixed number.

theres a problem 2 3/4= ?/4 what do i do?

2007-10-27 16:42:56 · 7 answers · asked by dancemagic95 2 in Mathematics

Wuts 10% of $250.00

2007-10-27 16:41:02 · 8 answers · asked by Joshua P 1 in Mathematics

was the neil armstrong moon landing real or fake???

2007-10-27 16:36:19 · 11 answers · asked by DJ SAINT 1 in Astronomy & Space

I caught the tail end of a conversation on the World Series tonight and I was wondering the physics and maybe chemistry causing the differences in the way a ball would "break" at higher and lower altitudes.

2007-10-27 16:29:25 · 4 answers · asked by whoadi7767 2 in Physics

I have never been able to find a precise answer to this, in angstroms on the visible solar spectrum....except that hydrogen radiates at many different frequencies across the board, whereas magnesium and sodium appear to emit at green and yellow frequencies.
In comparing the colors of gems, for instance, the elements that each are composed of don't seem to tally with what I'd expect from the color frequency they reflect.

* 6 days ago
* - 1 day left to answer.

2007-10-27 16:28:20 · 3 answers · asked by +-+-+-+-+- 4 in Astronomy & Space

i'm doing a science fair in school, and my partner and i chose the effect of genes on skin color. We decided to use plants, we turned in out forms then we realized we didn't know how to cross two plants...lol...we want to use a white rose and red rose..if you have any idea on how to get the two plants to reproduce, it will be really helpful!

2007-10-27 16:26:49 · 6 answers · asked by young truth 2 in Botany

2007-10-27 16:20:19 · 3 answers · asked by Anonymous in Medicine

2007-10-27 16:19:04 · 4 answers · asked by nikeboy9_1 1 in Mathematics

if so why?...Whats the purpose?

2007-10-27 16:16:23 · 6 answers · asked by 2sweet 1 in Mathematics

Sharks can attack people, but chose not to! I mean, we're too boney for them, and don't tast good at all. The only reason that 2002 was called Summer of the Shark is because nothing important was going on, and the media decided to pick on sharks. The usual thing that they never report, like someone working with a shark getting bit on the hand or something, was reported. Just because sharks can be dangerous doesn't they always are!

Imagine, you're in the water with Carcharodon carcharias (aka Great White Shark), and it looks peaceful. It doesn't want to hurt you, but it's swimming next to you. Not attacking you, not wanting to hurt you, but swimming with you. It would be so cool to do that because you'ld be swimming with the creature that you were taught, your whole life to fear and it's not hurting you.

Can you answer my question now?
P.S. If you haven't figured it out by now...

... I LOVE SHARKS!!!

2007-10-27 16:13:47 · 14 answers · asked by Anonymous in Zoology

??

2007-10-27 16:10:49 · 5 answers · asked by Anonymous in Engineering

2007-10-27 16:10:01 · 7 answers · asked by oneakmusic 2 in Other - Science

Solve each of the following systems of linear inequalities graphically.

3x-y is less than or equal to 6,
x is greater than or equal to 1,
y is less than or equal to 3

2007-10-27 16:07:25 · 1 answers · asked by jamie2192003 1 in Mathematics

like, the moneran and plantae etc., but about the bacteria?? are bacteria a kingdom as well?

2007-10-27 16:06:14 · 2 answers · asked by Anonymous in Biology

Hotter than the Saudi oil fields. Is it any coincidence that the north pole is melting?

2007-10-27 16:05:50 · 6 answers · asked by phil8656 7 in Earth Sciences & Geology

A 540 gm rock is whirled on the end of a string 45 cm long which will break under a tension of 32 N.
a) What is the highest speed the rock can reach before the string breaks? (Neglect gravity.)

vmax = m/s
b) If two other strings identical to the first were attached to the rock, how fast could the rock be whirled before the three strings would break?

v'max = m/s
Next the rock is held by two of the same 45 cm strings with ends 63 cm apart and whirled in a circle between them. Neglect gravity.

c) What is the radius of the circle of motion?

R = cm
d) Now what is the maximum speed the rock can have before the string breaks?

v''max = m/s

2007-10-27 16:05:25 · 1 answers · asked by Anonymous in Physics

2007-10-27 16:05:24 · 4 answers · asked by charles f 1 in Engineering

The figure shows two identical blocks tied together with a string which passes over a pulley at the crest of the inclined planes, one of which makes an angle q1 = 29° to the horizontal, the other makes the complementary angle q2 = 61°.
a) If there is no friction anywhere, with what acceleration do the blocks move?

a = m/s2
b) If each block has a mass m = 0.7 kg, what is the tension in the string while they are both moving?

T = N
c) Now suppose the coefficient of sliding friction between the blocks and planes is µ = 0.03. With what acceleration do the blocks move in this case?

af = m/s2

2007-10-27 16:04:37 · 1 answers · asked by Anonymous in Physics

ok well i'm doing this science fair project and my sister
did one before too on the same subject, fingerprints.
her idea was what kinds of surfaces do fingerprints best show up on.
i want to do it on the same subject but different idea, so my teacher doesnt get the wrong idea of me coping the same thing.

please help asap. THANX

2007-10-27 16:04:12 · 5 answers · asked by me 3 in Other - Science

Without using a calculator, use the properties of inverse functions to find the exact value of the expression.

sin(arcsin 0.7)

i don't just need the answer, can you help expalain it as well? thanks

2007-10-27 15:59:38 · 6 answers · asked by Anonymous in Mathematics

A small block of mass m = 0.50 kg is fired with an initial speed of v0 = 4.5 m/s along a horizontal section of frictionless track, as shown in the top portion of Figure P7.58. The mass then moves along the frictionless semicircular, vertical tracks of radius R = 1.6 m.

(a) Determine the magnitude of the force exerted by the track on the block at points A and B.

track force at A? N

track force at B ? N

(b) The bottom of the track consists of a section (L = 0.40 m) with friction. Determine the coefficient of kinetic friction between the block and that portion of the bottom track if the block just makes it to point C on the first trip. [Hint: If the block just makes it to point C, the force of contact exerted by the track on the block at that point should be zero.]


here the figure...

http://img.photobucket.com/albums/v372/smilytwinkle/p7_58.jpg

i really need help on this...it so complicated...please help..thanks

2007-10-27 15:57:45 · 1 answers · asked by pinkepromise 2 in Physics

Do all parts of the world have same rainy season?
On what factors do rainy season depend?

Is it always just after summer?

I don't get this rain basics at all..

2007-10-27 15:56:03 · 2 answers · asked by learner 1 in Weather

2007-10-27 15:50:06 · 1 answers · asked by dark angel 1 in Biology

The real question I'm trying to ask is HOW EXACTLY DO THEY RESPOND WHEN A REIKI PRACTIONER MERELY WALKS THROUGH A STABLE??

It's obviously understandable why they'd respond to reiki treatments like anyone/anything else
PLEASE DESCRIBE HOW THE HORSE[S] REACT when you [if your a practioner or reiki] just walks thru the stable?
thanks
coz so far it seems to me, horses only have a few reactions
just can't imagine them having a wider range of reactions other than I've observed

2007-10-27 15:45:57 · 7 answers · asked by Yvonne 4 in Paranormal Phenomena

2007-10-27 15:45:45 · 11 answers · asked by keyser soze 3 in Physics

I remember arround 1998 or 1999, in Irvine California, seeing a asteriod on fire flying through the sky going east in Orang County int eh middle of the day. It looked like a rocket but it was in fire. Its been so long but i cant get it out of my head, it was one of the weirdest things i have ever seen. It must have hit somewhere east of Irvine maybe in Riverside. I wonder if it was on the news or if anyone else saw it? Im gonna try and google it and see if anything comes up.

2007-10-27 15:44:17 · 2 answers · asked by Pierce 2 in Astronomy & Space