Science & Mathematics - 7 September 2007

I got into a discussion with a friend of mine who claimed it had been proven; I disagreed because it is still called a "theory" as far as I know. If it has been proven would you please cite a source?

2007-09-07 11:34:41 · 15 answers · asked by Anonymous in Astronomy & Space

A basketball player who is 2.00 m tall is standing on the floor L = 13.0 m from the basket, as in Figure P4.52. If he shoots the ball at a 38.0° angle with the horizontal, at what initial speed must he throw so that it goes through the hoop without striking the backboard? The basket height is 3.05 m

2007-09-07 11:32:56 · 2 answers · asked by ひいらぎ 5 in Physics

answer with reference to structure and bonding

2007-09-07 11:31:37 · 6 answers · asked by Mona 2 in Chemistry

the question is to find the width of a piece of 10 by 10 cm aluminum foil. the foil weighs 0.4 g. the teacher gave a hint by saying it has something to do with the density of the foil, which is given on the periodic table.

any help plz?

2007-09-07 11:30:45 · 5 answers · asked by Anonymous in Chemistry

A battery-powered light bulb has a tungsten filament. Immediately after the switch connecting the bulb to the battery is turned on and the temperature of the bulb is still 20 degrees C, the current in the bulb is 0.860 A. After the bulb has warmed up to its operating temperature the current is 0.220 A.
What is the operating temperature of the filament?

Where do I go with this? Do I need the resistance of tungsten at 20 deg C (5.25x10^-8 ohm*meter)? Is there a simple formula or ratio I'm missing?

2007-09-07 11:29:51 · 2 answers · asked by kev0709 2 in Engineering

2007-09-07 11:24:46 · 7 answers · asked by Anonymous in Astronomy & Space

2) A tennis ball with a speed of 12.6 m/s is thrown perpendicularly at a wall. After striking the wall, the ball rebounds in the opposite direction with a speed of 10 m/s. If the ball is in contact with the wall for 0.014 s, what is the average acceleration of the ball while it is contact with the wall?
I thought the answer was 1614.29 m/s^2 but it wasn't right. Could somebody please help me!!

2007-09-07 11:24:12 · 3 answers · asked by lola 1 in Physics

A 2-digit number is one more than 6 times the sum of its digits. if the digits are reversed, the new number is 9 less than the original number. find the original number


i need an equation for this


thanks

2007-09-07 11:21:24 · 2 answers · asked by Xin Zhou 2 in Mathematics

Hello
I was about to solder several 2N2907 and 2N304 transistors to a PCB, but I was surprised to see the instructions for the kit I was assembling made no recommendation for the use of heat sinks. Can I safely solder these transistors onto the board without frying them, without the use of some sort of heat sink?

2007-09-07 11:19:12 · 9 answers · asked by tom h 3 in Engineering

4(2x – 3) = 3x + 13

2007-09-07 11:14:23 · 12 answers · asked by Anonymous in Mathematics

evalluate the expression:
x^3+x^2+x when x= -3

simplify the expression:
3x-(4y-3x)-4y

and can you plz tell me when solving an inequality equations...why sometimes the symbol is reversed?

plz tell me

2007-09-07 11:10:21 · 3 answers · asked by Anonymous in Mathematics

i have this wksht. for earth science (im a freshman) and i have to match the measurements with the items, or places. measurements are: 1 cm, 10 cm, 1 m, 10m, 100m, 1 km, 10 km, 100km, 1000 km, 10,000km, 100,000km, 1 million km, 10 million km, 100 million km, & 1 billion km. the objects place things are: basketball, classroom, deepest depth or pacific ocean, denver to kansas city, depth of grand canyon, distance of sun from earth, earth to moon, earths diameter, height of a doorway, height of mt. everest, jupiters diameter, length of california, milky way galaxy, moons diameter, nashville to nyc, nearest star(other than sun), ping pong ball, san fransisco to new york, softball, sun to saturn, suns diameter, the high school, width of a door, and width of a light switch lever
so i have to match the places/objects with the measurements
thanks!

2007-09-07 11:09:03 · 3 answers · asked by Anonymous in Astronomy & Space

A classmate of mine saw a video of a mineral oil submersed computer and im slightly skeptical about the idea, he wants to build one for a school, but i need to know if the mineral oil is conductive and if the website is pulling legs.

2007-09-07 11:06:27 · 7 answers · asked by TheBlueBeast 2 in Chemistry

I was looking at Google Earth in Nevada (south of where my sister, brother-in-law, neices, cousins live) and saw what looks like HUNDREDS of test craters and even more underground sites. What were we learning? Nearly all of these gave off radioactive clouds, which drifted as far as the Mississippi...

2007-09-07 11:02:29 · 24 answers · asked by Faesson 7 in Engineering

what are the mole fraction of benzene (C6H6), and toluene (C7H8),in a solution prepared by adding 500 g of benzene to 500g of toluene?
plz someone explain it!!!!

2007-09-07 10:58:14 · 2 answers · asked by Anonymous in Chemistry

thank you so mutch kk

2007-09-07 10:53:28 · 5 answers · asked by kimberly k 1 in Mathematics

plz someone explain it!!!!

2007-09-07 10:51:33 · 1 answers · asked by Anonymous in Chemistry

Also, what about the Gaia theory of the earth?
Also which reptile is most closely related evolutionarily to birds?

2007-09-07 10:50:59 · 3 answers · asked by Caysie101 5 in Astronomy & Space

A group of students decides to sell pizzas to help raise money for their senior class trip. They sold pepperoni for $12, sausage for $10, and cheese for $8. At the end of their sales the class sold a total of 600 pizzas and made $5900. The students sold 175 more cheese pizzas than sausage pizzas. Set up a system of three equations and three unknowns, use an augmented matrix to solve, and show all work to receive full credit.

A. What are the three unknowns?

B. Write a separate equation representing each of the first three sentences.

C. Determine the augmented matrix that represents the three equations.

D. Solve for the matrix. Show all work.


E. How many of each type of pizza were sold?

2007-09-07 10:48:05 · 2 answers · asked by Anonymous in Mathematics

2007-09-07 10:46:23 · 8 answers · asked by Lee B 1 in Botany

2007-09-07 10:44:00 · 2 answers · asked by b 1 in Mathematics

2007-09-07 10:40:59 · 7 answers · asked by RogerDodger 1 in Physics

2007-09-07 10:35:45 · 5 answers · asked by ahn 1 in Mathematics

ok so, i have a mean prof who wants this worked out asap. if you could just give my the general walk through or hints to what i need to do, that would be awesome, i've read the chap and such still don't understand how. oh by that way this is what i am given thank you soooo much!
boiling pt of solute=89.0C,
H2O=100C,
M(unknown)=4.41g,
M(h2o)= 99.72g .
Kb(C/m)=.52(H2o)

NaCO3=105.99 g/mol
NaHCO3=84.008g/mol
NA3PO4=163.94g/mol
KHC8H4O4=116.22g/mol

2007-09-07 10:34:30 · 1 answers · asked by Anonymous in Chemistry

Why can't they "mate" all-year round, but humans can?

2007-09-07 10:33:33 · 6 answers · asked by Anonymous in Zoology

2007-09-07 10:33:04 · 5 answers · asked by Anonymous in Engineering

Still viable for life? Evolution? Other Effects? Specifically, would the vegetation be different, the geology, navigation, etc?

2007-09-07 10:31:54 · 8 answers · asked by Mandrake 1 in Earth Sciences & Geology

In complete sentences, and paragraph form.
..Explain in words how to evaluate the expression
5[(6+3then a power 2) -14 / 7]
according to the order of operations.
Helppp.
and the power thing..which is 3 times 3
i just couldnt write a small 2 right by the 3

2007-09-07 10:31:43 · 4 answers · asked by ? 3 in Mathematics

plz someone explain it!

2007-09-07 10:27:51 · 1 answers · asked by shima 1 in Chemistry

UMM. i NEED help ummm help me find three different ways to do 729 AND 15,625 in a POWER!!!!!

2007-09-07 10:23:34 · 6 answers · asked by Anonymous in Mathematics