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#2491 MillerGenuineDraft

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Posted 19 November 2010 - 01:52 AM

Well the time it takes for the arrow to get there is determined from the horizontal velocity and distance.

40.0m/90.0m/s=.444s

There was some formula of d=vit + 1/2at^2

vit=0
so d=1/2(9.8m/s^2)(.444s)^2=something

He has to be that distance above because gravity will pull the arrow down. He fires horizontally so don't worry about initial velocity.



Thanks so much man ! :D
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#2492 GoaltenderInterference

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Posted 21 November 2010 - 03:34 AM

Could someone please explain how to do this question?

3. The demand function for a company's product is p=60 000(x + 3000)-1, with demand 3000 units weekly.
a) Compute the elasticity of demand at the current demand.
B) Should the company raise or lower the price if it wants to increase revenue?
c) What price will maximize revenues? What will be the demand at this price?
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#2493 no vacancy

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Posted 21 November 2010 - 12:01 PM

Could someone please explain how to do this question?

3. The demand function for a company's product is p=60 000(x + 3000)-1, with demand 3000 units weekly.
a) Compute the elasticity of demand at the current demand.
B) Should the company raise or lower the price if it wants to increase revenue?
c) What price will maximize revenues? What will be the demand at this price?


i don't know a lot about economics but i think i can take a shot at this.

elasticity is defined as Ed = (p/x)*(dx/dp), where p is price and x is demand. so solve the equation you have above for x in terms of p and take the derivative:

Ed = (p/x)*(dx/dp) = (p/x) * d/dp[ 60000/p -3000 ] = (p/x) * (-60000/p2) = -60000/(px) = -(x + 3000)/x

now, evaluate for x = 3000 and you have Ed = -2.

as expected it's negative since demand goes down as price goes up, and it's magnitude is larger than 1 which means that fractional change in demand is larger than the fractional change in price when a change in price is made. hence an increase in price leads to a decrease in revenue, so the company should decrease the price to increase revenue.

now, revenue r = x*p. so that gives

r = 60 000x*(x + 3000)-1

now, this doesn't have a maximum for any value of x. it starts approaches 60000 asymptotically ( x/(x+3000) is always less than 1). so i suppose for part © the answer would be that no such price exists? or is there something i'm missing?

Edited by no vacancy, 21 November 2010 - 12:03 PM.

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#2494 GoaltenderInterference

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Posted 21 November 2010 - 10:25 PM

i don't know a lot about economics but i think i can take a shot at this.

elasticity is defined as Ed = (p/x)*(dx/dp), where p is price and x is demand. so solve the equation you have above for x in terms of p and take the derivative:

Ed = (p/x)*(dx/dp) = (p/x) * d/dp[ 60000/p -3000 ] = (p/x) * (-60000/p2) = -60000/(px) = -(x + 3000)/x

now, evaluate for x = 3000 and you have Ed = -2.

as expected it's negative since demand goes down as price goes up, and it's magnitude is larger than 1 which means that fractional change in demand is larger than the fractional change in price when a change in price is made. hence an increase in price leads to a decrease in revenue, so the company should decrease the price to increase revenue.

now, revenue r = x*p. so that gives

r = 60 000x*(x + 3000)-1

now, this doesn't have a maximum for any value of x. it starts approaches 60000 asymptotically ( x/(x+3000) is always less than 1). so i suppose for part © the answer would be that no such price exists? or is there something i'm missing?


The formula is -(p/x)(dx/dp) so the answer is 2. (Thanks I got the gist of it though!)

And for C, the answer in my book is "E=1 cannot be attained", so I think you're right.

Thanks again :)

Edited by GoaltenderInterference, 21 November 2010 - 10:27 PM.

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#2495 MillerGenuineDraft

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Posted 29 November 2010 - 12:04 AM

I have a math unit test tomrw, and need some help guys! Thanks :)

Solve for f(f(x)):

a ) f(x)= (1)/(1-x) where x cannot equal 1

b ) f(x)= (x-1)/(x+1) where x cannot equal -1

The answers are:
a ) (x-1)/x
b )-(1/x)

Edited by ~luongo~, 29 November 2010 - 12:04 AM.

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#2496 no vacancy

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Posted 29 November 2010 - 02:52 AM

I have a math unit test tomrw, and need some help guys! Thanks :)

Solve for f(f(x)):

a ) f(x)= (1)/(1-x) where x cannot equal 1

b ) f(x)= (x-1)/(x+1) where x cannot equal -1

The answers are:
a ) (x-1)/x
b )-(1/x)



to evaluate f(f(x)) (the composition of f with itself) you just need replace all the x in the expression for f(x) with f(x) itself, and then simplify. you may also see questions like f(g(x)) etc., and the method is the same. just think about replacing the independent variable x with whatever function/expression is given inside the brackets.


for a), f(x) = 1/(1-x). so f(f(x)) = 1/(1-f(x)).

first consider 1 - f(x).

1 - f(x) = 1 - 1/(1-x) = [(1-x)/(1-x)] - [1/(1-x)] (create a common denominator)
= (1 - x - 1)/(1-x) (combine terms)
= -x/(1-x)

then, 1/(1-f(x)) = 1/(-x/(1-x)) = (1-x)/(-x) = (x-1)/x.


b ) f(x) = (x-1)/(x+1), f(f(x)) = (f(x)-1)/(f(x)+1)

f(x) - 1 = (x-1)/(x+1) - 1 = (x-1)/(x+1) - (x+1)/(x+1) = (x -1 - (x + 1))/(x+1) = -2/(x+1)

f(x) + 1 = (x-1)/(x+1) + 1 = (x-1)/(x+1) + (x+1)/(x+1) = (x -1 + (x + 1))/(x+1) = 2x/(x+1)

then (f(x)-1)/(f(x)+1) = [-2/(x+1) ]/ [2x/(x+1)] = -1/x

Edited by no vacancy, 29 November 2010 - 02:53 AM.

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#2497 Conservative

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Posted 16 December 2010 - 09:52 PM

What is (OH-) in pure water if the ph is 7.4
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#2498 -Goose-

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Posted 16 December 2010 - 10:58 PM

What is (OH-) in pure water if the ph is 7.4

There's your hint.

Hydrogen ion concentration is equivalent to Hydroxide ion concentration when it's pure water.
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#2499 Minion

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Posted 11 January 2011 - 08:20 PM

A motor having an efficiency of 88% operates a crane having an efficiency of 42%. With what constant speed does the crane lift a 410kg crate of machine parts if the power supplied to the motor is 5.5kW?

So I figured out that the output energy of the motor is the input of the crane. Also that I have to somehow use P=W/t except I don't have any time or displacement? Help? :)
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#2500 Denguin

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Posted 29 January 2011 - 08:41 PM

Chemistry help much needed!


A sample of sodium hydroxide, NaOH, is known to have become contaminated with sodium carbonate, Na2CO3, by reaction with CO2 in the air.

A 1.00 g sample is titrated with 0.500M HCl and it is found that 48.6mL of HCl are required for neutralization. Calculate the percentage by mass of Na2CO3 in the sample. ( Hint: Let mass of Na2CO3 = x g. )




So far I have:

HCl + NaOH --> NaCl + H2O
2 NaOH + CO2 --> Na2CO3 + H2O

0.500M HCl x 0.0486 L HCl = 0.0234 mol HCl.

Since mol HCl = mol NaOH, mol NaOH = 0.0234 mol.

0.0234 mol NaOH x (40.0g/1 mol) = 0.972g


From here, is it simply just 1.00g - 0.972g? Or do I need to do a little more work with the stoichiometric ratios to achieve an answer? Also, with regards to the "hint" the question gave, where does that fit in to the question?



Thanks in advance!

Edited by Denguin, 29 January 2011 - 08:43 PM.

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#2501 GoaltenderInterference

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Posted 30 January 2011 - 01:03 AM

Can someone please help me simplify this question, using the properties of Boolean algebra?

A'BC + AB'C + ABC + A'B'C'

and

Draw a circuit diagram corresponding to the following Boolean expression.

ABC + C'B'

Also show the truth table.

Thanks in advance!

Edited by GoaltenderInterference, 30 January 2011 - 01:19 AM.

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#2502 MadMonk

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Posted 30 January 2011 - 09:09 AM

Chemistry help much needed!


A sample of sodium hydroxide, NaOH, is known to have become contaminated with sodium carbonate, Na2CO3, by reaction with CO2 in the air.

A 1.00 g sample is titrated with 0.500M HCl and it is found that 48.6mL of HCl are required for neutralization. Calculate the percentage by mass of Na2CO3 in the sample. ( Hint: Let mass of Na2CO3 = x g. )




So far I have:

HCl + NaOH --> NaCl + H2O
2 NaOH + CO2 --> Na2CO3 + H2O

0.500M HCl x 0.0486 L HCl = 0.0234 mol HCl.

Since mol HCl = mol NaOH, mol NaOH = 0.0234 mol.

0.0234 mol NaOH x (40.0g/1 mol) = 0.972g


From here, is it simply just 1.00g - 0.972g? Or do I need to do a little more work with the stoichiometric ratios to achieve an answer? Also, with regards to the "hint" the question gave, where does that fit in to the question?



Thanks in advance!

Does Na2CO3 react with HCl?
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#2503 Don't.Mess.With.Kes<3

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Posted 30 January 2011 - 11:46 AM

I have a biology mid term in a week. It covers digestion, bio-chem, nervous system and DNA etc. Any tips on best ways to study?
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#2504 Denguin

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Posted 30 January 2011 - 12:32 PM

Does Na2CO3 react with HCl?

I believe it can, yes. Eh, now I'm even more confused.
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#2505 MadMonk

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Posted 31 January 2011 - 09:09 AM

I believe it can, yes. Eh, now I'm even more confused.

A sample of sodium hydroxide, NaOH, is known to have become contaminated with sodium carbonate, Na2CO3, by reaction with CO2 in the air.

A 1.00 g sample is titrated with 0.500M HCl and it is found that 48.6mL of HCl are required for neutralization. Calculate the percentage by mass of Na2CO3 in the sample. ( Hint: Let mass of Na2CO3 = x g. )

So far I have:

HCl + NaOH --> NaCl + H2O
2 NaOH + CO2 --> Na2CO3 + H2O

0.500M HCl x 0.0486 L HCl = 0.0234 mol HCl.

Since mol HCl = mol NaOH, mol NaOH = 0.0234 mol.

0.0234 mol NaOH x (40.0g/1 mol) = 0.972g

I think you are on the right track, and you just have to include the reaction of the sodium carbonate.

If you follow the hint, and let x to be the mass of Na2CO3, you can convert that into mols, and find out how many mols of HCl is needed to neutralize the Na2CO3.
You can do the same for NaOH (say it is y g).

You have two unknowns x and y, and you'll need two equations to solve for the unknowns. You've already figured out one (i.e. the total amount of HCl available is 0.0234 mol), and what is the other?
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#2506 Conservative

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Posted 16 February 2011 - 11:03 PM

I never liked logarithms, don't remember the steps to solve equations like this:
e^x - e^-x = 0

It's probably something trivial, but I just don't remember
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#2507 -Goose-

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Posted 17 February 2011 - 12:08 AM

ln(e^(x)) = x
x - (-x) = 0
2x = 0
x = 0

For this you don't even need to know nat logs, there is an alternative method if you're good with fractions and
exponent laws.
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#2508 Des!Munda DrippinLik3Fanta

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Posted 18 February 2011 - 04:17 PM

I need some chem help.

A rectangular metal tray that measured 22.55cm by 15.33cm was plated with a very thin layer of gold.(The density of gold is 19.32g/cm^3) The gold plating had a mass of 0.0538g. Calculate the thickness of the plating using scientific notation and correct SIG FIGS.

please. :(
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#2509 Adikt

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Posted 18 February 2011 - 04:30 PM

I need some chem help.

A rectangular metal tray that measured 22.55cm by 15.33cm was plated with a very thin layer of gold.(The density of gold is 19.32g/cm^3) The gold plating had a mass of 0.0538g. Calculate the thickness of the plating using scientific notation and correct SIG FIGS.

please. :(


Given the mass of the gold plating, find the total volume of the gold plating using the density. Once you have the total volume of the gold plating, use the area of the tray which will leave you with the thickness.
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#2510 Don't.Mess.With.Kes<3

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Posted 18 February 2011 - 05:57 PM

Has anyone read one flew over the cuckoos nest? I have to write an essay on what I think the theme of the book is and I'm not sure what to write about. Maybe the theme of power or insanity vs sanity. Any ideas?
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#2511 Don't.Mess.With.Kes<3

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Posted 18 February 2011 - 06:01 PM

I read that book in English last semester, solid book.

So any suggestions to the theme?
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#2512 Don't.Mess.With.Kes<3

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Posted 18 February 2011 - 06:06 PM

Google it. :D

You could say that to every homework question people have asked here lol. Ya I've looked and there's a few themes people have said but I want to see if I can get another opinion and also see if maybe someone here has had the same assignment
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#2513 Dw182

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Posted 18 February 2011 - 07:21 PM

Philosophy/Physics question. I'm doing a paper on Copernicus and Aristotle on their theory oh physics (more specifically, their contradictions of a heliostatic and a geostatic views on the earth). Would anyone be able to point me in the right direction as to how their views ran under the same assumptions? I can find enough differences between them, but one of the parts of the questions asks me what common assumptions they had for their views for their era. Thanks :)
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#2514 KoreanHockeyFan

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Posted 19 February 2011 - 06:04 PM

With Term 2 ending soon, and myself getting my final chances to get my marks up as high as I can for university acceptance, I need some tips on focusing on my homework.

Recently, I've ended up doing them last minute and it's causing me to lose easy marks. Why last minute? Because of my damn computer. I end up browsing around on YouTube for hours, and when I mean for hours, I actually mean, FOR HOURS. I recently thought of an idea of forcing myself to pull the plug off my router except that...I have a History project and I need the Internet obviously for some research. Now when I end up doing this, I go on Google, Wikipedia, or whatever. I get on those sites, then I click on one link, then another, then another...I think many of you have experienced this and it's completely screwing me up right now.

So, any tips on how to deal with this browsing addiction?
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#2515 Dorkey

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Posted 19 February 2011 - 06:10 PM

Self control my friend
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#2516 trek

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Posted 19 February 2011 - 06:10 PM

Block CDC, YouTube, Twitter, FACEBOOK in your hosts file.
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#2517 KoreanHockeyFan

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Posted 19 February 2011 - 06:15 PM

Block CDC, YouTube, Twitter, FACEBOOK in your hosts file.


Noob question: hosts file?
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#2518 trek

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Posted 19 February 2011 - 06:23 PM

Noob question: hosts file?

Open Command Prompt, type:

notepad C:\Windows\System32\Drivers\etc\hosts

Then paste these in at the bottom of the file:

127.0.0.1 facebook.com
127.0.0.1 forum.canucks.com
127.0.0.1 twitter.com
127.0.0.1 youtube.com

Then save. To restore access, just delete those lines and then resave.

Edited by trek, 19 February 2011 - 06:24 PM.

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#2519 -Goose-

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Posted 19 February 2011 - 06:28 PM

Or just picture yourself as a failure if you don't do well. That should help motivate you.
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#2520 -Goose-

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Posted 19 February 2011 - 06:30 PM

Philosophy/Physics question. I'm doing a paper on Copernicus and Aristotle on their theory oh physics (more specifically, their contradictions of a heliostatic and a geostatic views on the earth). Would anyone be able to point me in the right direction as to how their views ran under the same assumptions? I can find enough differences between them, but one of the parts of the questions asks me what common assumptions they had for their views for their era. Thanks :)


Both had a thing for Circular objects/motion. Particularity Copernicus - he had the idea that everything in nature was related to perfect shapes.
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