# Official BMGf Homework Tutor/Help Thread

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• 18th October 2010, 02:10 AM
Vagabunda
Re: Official BMGf Homework Tutor/Help Thread
Best subjects: English (reading comprehension and grammar) and math up to multivariable calculus
Credentials: I've never received less than an A in an English course, got a 36 on the reading section of the ACT, and I'm currently taking multivariable calculus. I'm a senior in high school.

I'll probably be on here for math or European History help :I

EDIT:
Also, I can help with basic Spanish.
I'm upto high-intermediate level comprehension.
• 18th October 2010, 07:52 AM
Pseudonym
Re: Official BMGf Homework Tutor/Help Thread
Quote:

Originally Posted by Heathcliff Huxtable
I'm not sure if I remember how to solve these kinds of problems but I'll give it a shot.

Assuming the heat of fusion for ice is 334 J/g, the amount of energy required to melt 100g of ice is (100g)*(334J/g) = 33400J. This amount of energy must be absorbed from the rest of the system. The following equation can be used to determine the temperature change of the water:

(q is the energy transferred, m is the mass of the substance, c is specific heat capacity of the substance, delta T is the change in temperature)

Substituting in all known values, we are left with

-33400J = (1000g)*(4.184J/g*C)*delta T

Solving for delta T, we have

delta T = (-33400J)/[(1000g)*(4.184J/g*C)] ≈ -7.98 degree C

Solving for the final temperature, we get

80 degree C + (-7.98 degree C) = 72.0 degree C

You can adjust these values for significant figures as you see fit. You also may want to check my work to see if I made any mistakes.

Yes, the problem is that I tried that too and it gave me the same result, but the book from which I'm doing the exercise says that the answer is 66 degree C.
• 18th October 2010, 09:14 AM
TheMissingno.
Re: Official BMGf Homework Tutor/Help Thread
Quote:

Originally Posted by pseudonym12
Yes, the problem is that I tried that too and it gave me the same result, but the book from which I'm doing the exercise says that the answer is 66 degree C.

Maybe the book is incorrect?

Quote:

Originally Posted by Rakarei
It seems to me we've got far more people volunteering to help than people looking for help.

I'm pretty sure no one would be able to help me with mine. -_-
• 18th October 2010, 04:20 PM
Vagabunda
Re: Official BMGf Homework Tutor/Help Thread
Quote:

Originally Posted by pseudonym12
Yes, the problem is that I tried that too and it gave me the same result, but the book from which I'm doing the exercise says that the answer is 66 degree C.

Let's see... 333.55 J/g * 100 g = 33355 J
Q = 100 g * 4.1813 J/(g*K) * 80 K
Q = 33450 J + 33355 J = 66805 J
-66805 J = 1100 g * 4.1813 J/(g*K) * dT
-66805 J = 4599.4 J/K * dT
-14.524 K = dT
80 C - 14.524 C = 65.48 C ~ 66 C

You have to account for heating the ice to 80 degrees. Then you incorporate the new mass in your later calculations.
• 18th October 2010, 05:09 PM
Rayne
Re: Official BMGf Homework Tutor/Help Thread
Quote:

Originally Posted by TheMissingno.

I'm pretty sure no one would be able to help me with mine. -_-

And what would that be out of curiosity? I wouldn't underestimate the experience of the people here so easily. ;)
• 18th October 2010, 06:09 PM
TheMissingno.
Re: Official BMGf Homework Tutor/Help Thread
Quote:

Originally Posted by Rayne
And what would that be out of curiosity? I wouldn't underestimate the experience of the people here so easily. ;)

(yay, now I get to brag!) Right now, turbulent flow. The first question on my assignment is "Derive Reynolds-averaged mass conservation equation and Newton’s second law for a fluid." That one isn't too bad, but it just gets worse from there.

If there are any aerospace engineering seniors or aerospace/mechanical engineering grad students out there, I'd love to get some help!
• 18th October 2010, 08:42 PM
Rayne
Re: Official BMGf Homework Tutor/Help Thread
F*cking fluids. I'm guessing this isn't as easy as finding Reyonld's Number is it? XD

I feel your pain, though thankfully we were not put through derivations. I'm a recent Civil Engineering grad, so yes, you aerospace and mechanicals can have your last laugh yet again for claiming to the superior studies. The best I can do is work it through with you, perhaps, though differentials and vectors were never left a good taste in my mouth. It seems you're going after Navier-Stokes, and I'm sure you've checked the Wiki on this, among other places, no?

That's where I'd start out if I were lost. Or just ask one of my aerospace friends to help >>
• 19th October 2010, 12:21 AM
Mintaka
Re: Official BMGf Homework Tutor/Help Thread
Best subjects : English comprehension (and learning more advanced now), Biology
Credentials: I learned biology since middle school so I think I can be of help. I always maintained a grade of A in the subject. A bit of chemistry too. Currently I am a freshman at college, biology major.

I think I'll take biology here as well as English. I can write essays pretty well.
• 19th October 2010, 02:25 AM
g3rgni
Re: Official BMGf Homework Tutor/Help Thread
Quote:

Originally Posted by lizzxxk
Let's see... 333.55 J/g * 100 g = 33355 J
Q = 100 g * 4.1813 J/(g*K) * 80 K
Q = 33450 J + 33355 J = 66805 J
-66805 J = 1100 g * 4.1813 J/(g*K) * dT
-66805 J = 4599.4 J/K * dT
-14.524 K = dT
80 C - 14.524 C = 65.48 C ~ 66 C

You have to account for heating the ice to 80 degrees. Then you incorporate the new mass in your later calculations.

Yeah, I had a feeling I was missing an important step. I forgot to assume that the ice and the water are no longer separate systems at the end of the problem.
• 19th October 2010, 07:48 PM
Frantic
Re: Official BMGf Homework Tutor/Help Thread
I was looking through this thread and sorry for asking such a basic question compared to the ones here, but can someone please explain WHAT THE **** IS A FLOW PROOF!!! I mean, I know what a 2-column proof and a paragraph proof are and how to do them, but can someone please explain what a flow proof looks like and how to do them please?
• 19th October 2010, 09:18 PM
Magmortar123
Re: Official BMGf Homework Tutor/Help Thread
Man, I wish I could help you there, but Geometry is my math weak point. If I remember correctly though, it's basically a proof where you draw arrows to your answer in the proof. Man this is difficult over a computer. So suppose you have Triangle ABC and it is Isosceles. You must Prove side "A" is equal to side "B" So you would solve accordingly, but draw arrows. Terribly sorry if I gave incorrect info, geometry is my weak point.
• 19th October 2010, 10:38 PM
Frantic
Re: Official BMGf Homework Tutor/Help Thread
Awesome! It sounds correct if you compare it to the name. But then again, that could just be my opinion. XD Well, thanks so much anyways. Now anytime I have school trouble, I'm coming here. ID
• 20th October 2010, 07:32 PM
CuboneKing
Re: Official BMGf Homework Tutor/Help Thread
I can help out with geography too.
• 21st October 2010, 07:50 AM
Morru Magnum
Re: Official BMGf Homework Tutor/Help Thread
Can anyone give me the complete chemical equation for these: (With the product side included.)

Magnesium Ribbon + Water
Iron Nail + Sulfuric Acid
Baking Soda + Vinegar
Chalk + Water
Chalk + Hydrochloric acid
Copper Filings + Concentrated sulfuric acid
zinc + Hydrochloric acid
Copper Sheets + Oxygen gas ->(heat)
Magnesium Ribbon + Oxygen gas ->(heat)
Calcium Carbide + H2O
Sulfur Powder + Oxygen gas ->(heat)
Sugar + Oxygen gas ->(heat)
Copper Sulfate Pentahydrate + Oxygen gas ->(heat)
Copper Sheets + Oxygen gas
• 21st October 2010, 09:26 PM
Rakarei
Re: Official BMGf Homework Tutor/Help Thread
Quote:

Originally Posted by MorruMaster14
Can anyone give me the complete chemical equation for these: (With the product side included.)

Magnesium Ribbon + Water
Iron Nail + Sulfuric Acid
Baking Soda + Vinegar
Chalk + Water
Chalk + Hydrochloric acid
Copper Filings + Concentrated sulfuric acid
zinc + Hydrochloric acid
Copper Sheets + Oxygen gas ->(heat)
Magnesium Ribbon + Oxygen gas ->(heat)
Calcium Carbide + H2O
Sulfur Powder + Oxygen gas ->(heat)
Sugar + Oxygen gas ->(heat)
Copper Sulfate Pentahydrate + Oxygen gas ->(heat)
Copper Sheets + Oxygen gas

Ummm... Maybe I don't know as much chemistry as I thought. Requesting to not be a chemistry tutor anymore.
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