Science & Mathematics - 3 October 2007

Radiactive Decay Half Life (T1/2)

In a collection of a great many identical radioactive isostopes, the half- life (T1/2) of the sample is the time it takes for half of the samples to decay.

Question: If the half life of a certain isotope is 4 years, what fraction of a sample of that isotope will remain after 12 years.

2007-10-03 07:44:48 · 2 answers · asked by pooey_1980 2 in Mathematics

I want to buy a telescope that will help me see other galaxies from earth. How much would this kind of telescope cost?

2007-10-03 07:44:02 · 10 answers · asked by Lazarus Cadaver 3 in Astronomy & Space

Why does sulphur powder react slowly with silver metal, but sulphide ions react quickly to form a precipitate with silver ions? Does it have to do with the states (solids vs. ions) or surface area?

2007-10-03 07:43:42 · 1 answers · asked by Jeff P 3 in Chemistry

It should be in the form y=mx+b.

2007-10-03 07:41:46 · 1 answers · asked by jvt022285 1 in Mathematics

2007-10-03 07:39:49 · 4 answers · asked by peachmelba 2 in Other - Science

2007-10-03 07:39:20 · 6 answers · asked by ♥ Ƹ̵̡Ӝ̵̨̄Ʒ 3 in Mathematics

2007-10-03 07:38:26 · 8 answers · asked by merz 3 in Biology

2007-10-03 07:36:37 · 3 answers · asked by Anonymous in Chemistry

I think they will died if they landed on venus or any other planet but anyways I had this dream about me being stuck in space an land on the planet venus, it had red clouds, wram weather and etc. Then I saw people but strange looking, they ask me where you came from I said Earth I didn't understand there language at all.

That was strange a dream! I believe that there are diffrent kind of human-beings living on other planets for venus, mercury, saturn, juipter and etc. We can't live there bc we are design to live on earth.

2007-10-03 07:35:33 · 8 answers · asked by Anonymous in Astronomy & Space

Calculate the concentration in molarity of a NaOH solution if 10 mL of the solution are needed to neutralize 21 mL of a .312 molar HCl solution?

2007-10-03 07:30:52 · 2 answers · asked by wasabi makes the world go round 1 in Chemistry

This is the question I have:
A ball is thrown at an angle of 45* to the ground. If the ball lands 90m away, what was the initial speed of the ball?

If someone could explain how to do this I would apreciate it. You don't have to give me the answer, just how to solve it. Thanks

2007-10-03 07:27:34 · 2 answers · asked by me06 2 in Physics

a peice of metallic Sn were placed in distilled water w/ metallic Zn? Explain? Write net ionic eq.

2007-10-03 07:27:03 · 1 answers · asked by PiNk-PrInCeSs 3 in Chemistry

Can anyone tell me some alternative theories to the big bang? (NOT "God made it"). Alternative scientific theories, and maybe some links to their wikipedia pages. Thanks

2007-10-03 07:26:17 · 9 answers · asked by Anonymous in Astronomy & Space

I have an air compressor hooked up to a ventilator and I'm trying to stop condensation/water from getting into the ventilator. I already have two water traps connected to the ventilator. Any ideas?

2007-10-03 07:15:48 · 1 answers · asked by Mark 1 in Other - Science

This is probably rele retarded. But I wana see them! :)

2007-10-03 07:13:47 · 8 answers · asked by cassioTRON :] #1 Stratus-fan! 3 in Astronomy & Space

without using an online calculator... I need to show work converting 21nm to ___ um

2007-10-03 07:13:44 · 2 answers · asked by bep 2 in Other - Science

and why?

2007-10-03 07:12:35 · 7 answers · asked by eyepopping hideous female troll 4 in Engineering

copper (II) oxide is reduced by hydrogen to copper and water:

CuO + H2 ---> Cu + H2O

What mass of copper(II) oxide will be reduced by excess hydrogen to give 16g of copper.

do i need to do:

mass = moles x molar mass?

thanks

2007-10-03 07:12:10 · 2 answers · asked by Anonymous in Chemistry

2007-10-03 07:11:26 · 9 answers · asked by missliberty5 1 in Geography

the equation balanced is (sorry about big numbers, they dont do small ones)

2AL(OH)3 + 3H2SO4 = AL2(SO4)3 + 6H2O

This is for As level chemistry. I had a go but the number appeared to be too big

2007-10-03 05:47:36 · 2 answers · asked by Anonymous in Chemistry

1. What is the 1,1-dimethylethyl group, -C(CH3)3, can also be called?

2. how many methine groups are there in isopropylcyclopentane?

3. What is the total # of constitutional isomers with the formula C5H12?

Detals, please

2007-10-03 05:46:25 · 2 answers · asked by Anonymous in Chemistry

My 8th grader is embarking down this frightful journey. Can I please get some ideas for his thesis statement, we can take it from there but I need as many ideas as I can get on what to experiment on.

2007-10-03 05:44:55 · 1 answers · asked by Anonymous in Other - Science

2007-10-03 05:42:55 · 7 answers · asked by Anonymous in Astronomy & Space

my precalc/trig teacher is gonna give extra credit to who ever can tell him what the sign is!!!

2007-10-03 05:41:16 · 3 answers · asked by noura s 2 in Mathematics

out of these choices
H2O
NaCl
CH1

2007-10-03 05:30:27 · 1 answers · asked by tc 1 in Chemistry

2007-10-03 05:29:33 · 4 answers · asked by Greetings! 3 in Botany

I work in utility construction. Many times we have to remove bolts and/or nuts that are rusted - "frozen tight!" - even after we spray them with various penetrating oils to "loosen them up."

How does this work? I put a wrench on the nut/bolt, pull as hard as I can. Nothing happens. Then I put a 5 ft. long pipe on the end of the wrench, pull on the end of the pipe (opposite side from wrench), and my "pulling" is 1/2 as hard, and the bolt/nut unscrews!!??

Sure, I understand this is called "leverage," but that does not make me understand WHY, with the pipe, I pull 1/2 as hard! I mean, the bolt/nut will STILL require more 'pull' than my arm can give, to 'break free,' but with the pipe, I see to "get-more-pull", with 1/2 the required strength.

This does not make sense. I guess I am saying, if you use a air wrench to tighten up the nut with 100 pounds of pressure, to remove it again -should require 100 pounds of pressure. My arm is pulling 50 pounds of pressure, so nothng happens!

2007-10-03 05:25:23 · 8 answers · asked by Anonymous in Engineering

My guess is that the answer is "the fabric of space-time", but how can there be "fabric" of anything if there is empty space.

2007-10-03 05:18:44 · 2 answers · asked by Anonymous in Physics

I want to get my nine year old son a telescope and a microscope for Christmas. He has tons of toys so his dad and I have been trying to figure out something good for him that he'd enjoy. I know he'd like these items. The problem is I have no idea of how to go about buying them. For instance, what is a good brand? What's a good one for kids? I looked on ebay and they had all this stuff along with the description that I didn't understand.

Does anyone know of a good brand for kids that's not real expensive?

2007-10-03 05:16:20 · 7 answers · asked by musicpanther67 5 in Astronomy & Space

hi
i am building a prepaid meter using a pic micro and i need a card reader to read the value stored on a smart card but i dont know the reader to use and where i can get some to buy.
if any body has done a smart card-microcontroller proj before please tell me which card reader u used and where i can get some to buy.
i also have to delete the data on the card after reading it
any help on that too?

2007-10-03 05:15:23 · 2 answers · asked by GILBERT M 2 in Engineering