Science & Mathematics - 2 December 2007

using the formulae d = |OA.OB|

where OA=[1,2,3]
OB=1/6[4,-4,-2]

there are many formulaes i found and im confused, is the answer -5/3(from doing 1X2+2X-4+3X-2...but thats the vector product)??
please show the working ,

2007-12-02 23:58:18 · 2 answers · asked by nack nack 3 in Mathematics

A person whose mass is 75 kg is lowered with a rope down the side of a cliff. The rope being used can support a maximum of 595 N. In order to prevent the rope from breaking, at what minimum rate must the person accelerate downward?

2007-12-02 23:57:08 · 8 answers · asked by Anonymous in Mathematics

STP is used only for gases. The standard state for thermodynamic data (including individual gases) is 25C, and either 1 atm or 10^5 Pa. Ideal gas calculations at college level are done using PV = nRT

So my question is, why do we teach STP at all?

2007-12-02 23:52:41 · 2 answers · asked by Facts Matter 7 in Chemistry

f(x)=2x²-3x-2=0

by using the discriminant b²-4ac

2007-12-02 23:50:53 · 1 answers · asked by Anonymous in Mathematics

A) The population of China is growing exponentially at a rate of 1.1% per year.
How long will it take China to double its population? _________________

B) The value of the property in S-ville decreases exponentially at a rate of 6.8% annually. The original value of the house was $150,000.
Write the function modeling the value of the house over time.
V(t) = _________________________________

2007-12-02 23:46:33 · 2 answers · asked by momof3 1 in Mathematics

If your on the moon and you drop a feather and a hammer at the same time its supposed land at the same time but how there is no gravity on the moon....

2007-12-02 23:44:42 · 8 answers · asked by Christle DeTurris<3 2 in Astronomy & Space

Do we have to wait until New Horizons probe gets there or is there a reasonable photo of this dwarf planet already? I've never seen one!

2007-12-02 23:44:20 · 3 answers · asked by Tony W 4 in Astronomy & Space

The membrane that surrounds a certain type of living cell has a surface area of 5.0 x 10^ -9 m^2 and a thickness of 1.0 x 10^ -8 m. Assume that the membrane behaves like a parallel plate capacitor and has a dielectric constant of 5.0. (a) If the potential on the outer surface of the membrane is +60.0 mV greater than that on the inside surface, how much charge resides on the outer surface? (b) If the charge in part (a) is due to K+ ions (charge +e), how many such ions are present on the outer surface?

2007-12-02 23:42:14 · 1 answers · asked by sunday 1 in Physics

A parallel plate capacitor has a capacitance of 7.0x 10^-6 F when filled with a dielectric. The area of each plate is 1.5 m^2 and the separation between the plates is 1.0 x 10^ -5 m. What is the dielectric constant of the dielectric?

2007-12-02 23:40:24 · 1 answers · asked by sunday 1 in Physics

What voltage is required to store 7.2 x 10^ -5 C of charges on the plates of a 6.0x10^ -6 F capacitor?

2007-12-02 23:33:40 · 1 answers · asked by sunday 1 in Physics

(polynomials)

I just want to check if i got the right answer

x^2+3x-18x-40=0

ty

2007-12-02 23:28:46 · 5 answers · asked by xMwahahahahahahax 3 in Mathematics

ITS urgent

2007-12-02 23:16:59 · 4 answers · asked by Anonymous in Engineering

5x-4y=8
6x-y=21
Exactly by analytical means

2007-12-02 23:11:25 · 7 answers · asked by Anonymous in Mathematics

we are learning about particles; bohr's model/diagram, ions, nomenclature... Isn't 8th grade early to learn about all of that? (at the same time as balencing equations, ionic/covalent bonds etc..)

When did YOU learn those things?

2007-12-02 23:05:43 · 5 answers · asked by Zobbiezob 3 in Chemistry

how did they know that the speed of electromagnetic wave is 300 000 000 meters per second?

2007-12-02 22:44:09 · 7 answers · asked by Anonymous in Physics

Ok, so I live in Texas and have had about enough warm weather and am just curious how seriously I should take a 15-day forecast, like on accuweather.com? I am just a little wary because I remember the week before Thanksgiving I was looking at various weather sites and they all said the high would be like 75 in Austin/Dallas and turns out come Thanksgiving, the high was 45 and the low was 30! I would say they were more than a little off. So, am I right to be skeptical?

2007-12-02 22:43:22 · 9 answers · asked by Madeline 2 in Weather

and how does my rock quartzite fit the definition explain why or why not

2007-12-02 22:35:03 · 5 answers · asked by bae_11_96 1 in Earth Sciences & Geology

This is our physics assignment so anybody could help me? thanks!

2007-12-02 22:32:26 · 7 answers · asked by James trighit 1 in Physics

Hi,

A gas stove generates heat from the combustion of methane:

CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) ΔH = -802 kJ

How many moles of methane would need to be reacted in order to heat 4.00 kg (~ 1 gallon) of water (Cs = 4.18 J/g-K) from room temperature (25° C) to boiling (100° C)?

I know you use the formula q=c*m*deltaT. How would you go about doing it though?


Thanks!

2007-12-02 22:32:07 · 1 answers · asked by Anonymous in Chemistry

Ln(x³)+3ln(x²)=2

Im completely suck

2007-12-02 22:28:26 · 8 answers · asked by Anonymous in Mathematics

A girl I know who is Christian likes to point out "miraculous" things like science doesn't know how cats purr and that with as much as we know about biology, that initial spark when the sperm enters the egg that causes life to start is completely unknown and unknowable by science.

Well I looked around and found the cat purring answer for the most part, but I am curious as to the answer of what exactly happens to "spark" life.

She also says that when you die there's a surge in electical activity right before death and she says it's the soul leaving but science can't figure that out either. Any info on that would be appreciated as well.

Links also welcome.

2007-12-02 22:23:44 · 6 answers · asked by Tony AM 5 in Biology

2007-12-02 22:18:25 · 2 answers · asked by rr 1 in Earth Sciences & Geology

why does thunder make noise???

2007-12-02 22:15:56 · 4 answers · asked by Anonymous in Weather

what interest rate is required in order that your money will trible in the next 20 years with semi annual compounding?

could someone please help me with this. thanks.

2007-12-02 22:15:13 · 3 answers · asked by Mathema-what?! 1 in Mathematics

Please help me with this problem... Pretty please...

A tree casts a shadow of 42ft. at the same time that a yardstick casts a shadow of 2ft. How tall is the tree?

additional query:
How does the conversion goes again?

Thank you ever so much in advance! God bless! ^^,

2007-12-02 22:13:24 · 8 answers · asked by Anonymous in Mathematics

2007-12-02 22:11:44 · 2 answers · asked by sagar 1 in Biology

2007-12-02 22:11:11 · 1 answers · asked by rr 1 in Earth Sciences & Geology

I dun get this math stuff

explain please so that a 12 year old would understand?

Thankyou.

2007-12-02 22:10:15 · 7 answers · asked by Anonymous in Mathematics

I would usually use my ruler, but my new one doesn't have inches.

2007-12-02 22:03:36 · 10 answers · asked by Anonymous in Mathematics

2007-12-02 22:01:18 · 5 answers · asked by Anonymous in Biology