please halp!

**Mafoo** · 06-09-2011, 02:52 PM

fucking fuck

i have a take home final for physics and im stuck on two of problems.
1.temp of the sun 6000K, find the temperature on the surface of the earth. use exact values of the constants such as the raidus of the sun, distance to earth, etc.

i got the values:
radius sun = 6.95*10^8m
radius earth = 6.37*10^6m
distance from earth to sun = 1.5*10^11m

i know you must relate temperature to power. and then using the inverse square relation ship of power over distance squared, find out how much of the energy actually hits the earth. really stuck, been trying out different equations to no avail.

2. (this ones weird, we didnt cover this in class)
a gas bubble from a deep underwater explosion oscillates with period T~p^a*d^b*e^c

p= static pressure
d= density of water
e= total energy of explosion
find a,b, and c

no idea

Captain Cannabis · 06-09-2011, 02:59 PM

Quote:

Originally Posted by Mafoo

fucking fuck

i have a take home final for physics and im stuck on two of problems.
1.temp of the sun 6000K, find the temperature on the surface of the earth. use exact values of the constants such as the raidus of the sun, distance to earth, etc.

i got the values:
radius sun = 6.95*10^8m
radius earth = 6.37*10^6m
distance from earth to sun = 1.5*10^11m

i know you must relate temperature to power. and then using the inverse square relation ship of power over distance squared, find out how much of the energy actually hits the earth. really stuck, been trying out different equations to no avail.

draw a nice diagram and figure out how much of the surface of the earth is getting energy from the sun. you should have a formula for how radiative energy is dissipated based on radius (hint: look for greek letter sigma)

i am assuming you are ignoring things like albedo and greenhouse effect, but if you aren't you will need to assume incoming energy is equal to outgoing energy.

Quote:

2. (this ones weird, we didnt cover this in class)
a gas bubble from a deep underwater explosion oscillates with period T~p^a*d^b*e^c

p= static pressure
d= density of water
e= total energy of explosion
find a,b, and c

this is a classic physics exam writing strategy, where you do something exactly the same as what you did in lectures except with different letters and everyone gets it wrong. my hint for this is that you don't have to know anything about the system (ie deep underwater explosions) to manipulate the formula you were given

good luck mafoo

**Mafoo** · 06-09-2011, 03:08 PM

I = (T^4)*sigma

sigma = stephan-bolzman = 5.67*10^-8 watts/m^2

i got that.

i managed to calculate the total energy emitted from the sun by the formula i just wrote, and then multiplying that value by the surface area of the sun. then i multiplied by 1/(distance from earth to sun)^2 to account for the energy spreading out as it moves away from the source. thats all fine.

would i multiply that by the surface area of the earth to get how much of the emitted energy actually hits the earth?(the value i obtained before this step had units of watts/m^2) i did that and then rearragned the intensity formula from above to find T, but the answer i get is fucking huge. way beyond any temperature that could happen on earth, even if i was accounting for the greenhouse effect.

moar hintz!

ive been following this, but the final result i get is extremely large i might be misunderstanding the steps though.

we never learned anything about osscillating bubbles, we learned about pendulums and springs. neither of which involved a pressure or density component

Captain Cannabis · 06-09-2011, 03:15 PM

its really too confusing to read a paragraph about how you calculated something. if you need more hints remember that only half of the sun faces the earth, and only half of the earth gets sunlight at any time. you are essentially trying to estimate the solar constant (you can look this up) and then relate it to the temperature of the earth

don't forget to be really careful about your units. you should get the temperature in K

**SageTree** · 06-09-2011, 03:18 PM

ABORT ABORT!!!! Free for all's core temp is getting too hot... ABORT ABORT!!!!!

The Don · 06-09-2011, 03:30 PM

Wolfram|Alpha: Computational Knowledge Engine ?

**Mafoo** · 06-09-2011, 03:35 PM

Quote:

Originally Posted by Captain Cannabis

its really too confusing to read a paragraph about how you calculated something. if you need more hints remember that only half of the sun faces the earth, and only half of the earth gets sunlight at any time. you are essentially trying to estimate the solar constant (you can look this up) and then relate it to the temperature of the earth

don't forget to be really careful about your units. you should get the temperature in K

ok that might be the problem. the page i found was using the entire surface area of each, which i thought seemed wrong.

im not as concerned about the last one, i know that very few people in my class will be able to get that and the test is curved. i know i can figure the first one out, thats why im so frustrated GRRR

adventure · 06-09-2011, 03:44 PM

God I love physics, but I am so bad at math... its the bane of my academic existence.

Lloydy · 06-09-2011, 03:46 PM

**SageTree** · 06-09-2011, 03:48 PM

Captain Cannabis · 06-09-2011, 03:58 PM

Quote:

Originally Posted by Mafoo

ok that might be the problem. the page i found was using the entire surface area of each, which i thought seemed wrong.

im not as concerned about the last one, i know that very few people in my class will be able to get that and the test is curved. i know i can figure the first one out, thats why im so frustrated GRRR

i'll be back later if you still need help. you should work on the 2nd question and ask for more specific help when you run into a problem. i am glad to help but not really willing to just give you the answers

The Rev · 06-09-2011, 04:03 PM

Problem #1

Problem #2

The Rev

fenderbender · 06-09-2011, 04:50 PM

just give him the answer capt you douche. jeeze.

It is his final, if he trys and still cant get it why not give him the answer and help instead of him getting a bad grade.

Some yahookan friend you are

Sorry mafoo, i just took physics 1 this past semester but it was algebra/trig based not calc and this shit aint ringing any bells.

adventure · 06-09-2011, 05:44 PM

Quote:

Originally Posted by Captain Cannabis

i'll be back later if you still need help. you should work on the 2nd question and ask for more specific help when you run into a problem. i am glad to help but not really willing to just give you the answers

Really dude, I think he gave it a few tries before typing it all out and looking for help here. Are you here to teach him some life lesson?

**SageTree** · 06-09-2011, 06:08 PM

Use the power of the Ward!!!!!

Mikey · 06-09-2011, 07:17 PM

major ward

Captain Cannabis · 06-09-2011, 08:00 PM

Quote:

Originally Posted by adventure

Really dude, I think he gave it a few tries before typing it all out and looking for help here. Are you here to teach him some life lesson?

its actually way better for him if he figures out how to start the problem on his own. i am more than willing to help guide him to the answer. it is really of no value if i just give it to him. its also easier for me since that way i don't have to do the problems myself. if he is going to take more physics classes, this is something he should figure out on his own.

also these questions, while they are challenging, are not unsolvable. sometimes when i have tough problems to solve i write down everything i know about them and then take a total break. the answer usually comes when you are doing something totally different than thinking about what the answer is.

fenderbender · 06-09-2011, 08:21 PM

yeah bro it's a final though. Not some homework study type shit. If he can't figure it out, he's not gonna learn it either.

Just give him the answer if it isn't already too late.

**Mafoo** · 06-09-2011, 08:32 PM

i think a big part of the problem was that i didnt know the stephan boltzman constant has units of watts/m^2*k^4

i was using just watts/m^2 because i found some stupid webpage... anyway im still working on it, hopefully i can pop out a real answer.

i left work early because its bugging me so much

deadline is tomorrow, so its not too late, and im game to struggle with it. im not a physics major so its not likely ill be needing this in the future, though.

ill start complaining more ferociously if i really cant get it

Mikey · 06-09-2011, 08:53 PM

do a back flip!

06-09-2011, 02:52 PM	#1 (permalink)
Mafoo nice daze Join Date: Nov 2005 Location: the anguish of anticipated transformation Posts: 5,975 Thanks: 3,776 Thanked 2,652 Times in 1,698 Posts	please halp! fucking fuck i have a take home final for physics and im stuck on two of problems. 1.temp of the sun 6000K, find the temperature on the surface of the earth. use exact values of the constants such as the raidus of the sun, distance to earth, etc. i got the values: radius sun = 6.9510^8m radius earth = 6.3710^6m distance from earth to sun = 1.510^11m i know you must relate temperature to power. and then using the inverse square relation ship of power over distance squared, find out how much of the energy actually hits the earth. really stuck, been trying out different equations to no avail. 2. (this ones weird, we didnt cover this in class) a gas bubble from a deep underwater explosion oscillates with period T~p^ad^be^c p= static pressure d= density of water e= total energy of explosion find a,b, and c no idea __________________ PLUR* For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return

06-09-2011, 03:08 PM	#3 (permalink)
Mafoo nice daze Join Date: Nov 2005 Location: the anguish of anticipated transformation Posts: 5,975 Thanks: 3,776 Thanked 2,652 Times in 1,698 Posts	I = (T^4)sigma sigma = stephan-bolzman = 5.6710^-8 watts/m^2 i got that. i managed to calculate the total energy emitted from the sun by the formula i just wrote, and then multiplying that value by the surface area of the sun. then i multiplied by 1/(distance from earth to sun)^2 to account for the energy spreading out as it moves away from the source. thats all fine. would i multiply that by the surface area of the earth to get how much of the emitted energy actually hits the earth?(the value i obtained before this step had units of watts/m^2) i did that and then rearragned the intensity formula from above to find T, but the answer i get is fucking huge. way beyond any temperature that could happen on earth, even if i was accounting for the greenhouse effect. moar hintz! ive been following this, but the final result i get is extremely large i might be misunderstanding the steps though. we never learned anything about osscillating bubbles, we learned about pendulums and springs. neither of which involved a pressure or density component __________________ PLUR For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return Last edited by Mafoo; 06-09-2011 at 03:17 PM.

06-09-2011, 03:15 PM	#4 (permalink)
Captain Cannabis safety word: more Join Date: Jul 2001 Location: m.i.a. Posts: 13,922 Thanks: 2,705 Thanked 3,174 Times in 1,812 Posts	its really too confusing to read a paragraph about how you calculated something. if you need more hints remember that only half of the sun faces the earth, and only half of the earth gets sunlight at any time. you are essentially trying to estimate the solar constant (you can look this up) and then relate it to the temperature of the earth don't forget to be really careful about your units. you should get the temperature in K __________________ fuck the monkeys

06-09-2011, 03:18 PM	#5 (permalink)
SageTree ~Kalyāṇa-mitrā~ Join Date: Sep 2000 Location: In Love Posts: 23,414 Blog Entries: 26 Thanks: 13,070 Thanked 6,769 Times in 4,664 Posts	ABORT ABORT!!!! Free for all's core temp is getting too hot... ABORT ABORT!!!!! __________________ "What's oppressive is letting your life be confined by old definitions of what everything is." -Zen Meister my_scatterheart YaHooka is.... Cannabis lovers from around the world pulling up a comfy chair, picking up a vaporizer, a bong, a brownie, a pipe, or a joint, getting high, stoned, buzzed or healthy. Uniting our minds in conversation...While Portraying a Positive Image of marijuana and marijuana users to the world. Treat your fellow YaHookans with kindness,respect and tolerance.

06-09-2011, 03:30 PM	#6 (permalink)
The Don You follow? Join Date: Sep 2001 Posts: 11,151 Thanks: 544 Thanked 781 Times in 426 Posts	Wolfram\|Alpha: Computational Knowledge Engine ? __________________ I am genuienly sad about my thanks:post ratio

06-09-2011, 03:44 PM	#8 (permalink)
adventure Adventure its good Join Date: Nov 2005 Location: Upstate NY Posts: 4,742 Thanks: 1,852 Thanked 1,467 Times in 1,093 Posts	God I love physics, but I am so bad at math... its the bane of my academic existence. __________________ Coming Full Range

06-09-2011, 03:46 PM	#9 (permalink)
Lloydy KTF Join Date: Oct 2003 Location: England Posts: 11,976 Thanks: 533 Thanked 2,479 Times in 1,140 Posts	__________________ Keep the red flag flying high

06-09-2011, 03:48 PM	#10 (permalink)
SageTree ~Kalyāṇa-mitrā~ Join Date: Sep 2000 Location: In Love Posts: 23,414 Blog Entries: 26 Thanks: 13,070 Thanked 6,769 Times in 4,664 Posts	__________________ "What's oppressive is letting your life be confined by old definitions of what everything is." -Zen Meister my_scatterheart YaHooka is.... Cannabis lovers from around the world pulling up a comfy chair, picking up a vaporizer, a bong, a brownie, a pipe, or a joint, getting high, stoned, buzzed or healthy. Uniting our minds in conversation...While Portraying a Positive Image of marijuana and marijuana users to the world. Treat your fellow YaHookans with kindness,respect and tolerance.

06-09-2011, 04:03 PM	#12 (permalink)
The Rev Clear Light Join Date: Oct 2002 Location: In my head, somewhere. Posts: 17,865 Thanks: 5,018 Thanked 5,421 Times in 2,865 Posts	Problem #1 Problem #2 The Rev __________________ Budforce - My Friend August 29, 1973- May 25, 2012

06-09-2011, 06:08 PM	#15 (permalink)
SageTree ~Kalyāṇa-mitrā~ Join Date: Sep 2000 Location: In Love Posts: 23,414 Blog Entries: 26 Thanks: 13,070 Thanked 6,769 Times in 4,664 Posts	Use the power of the Ward!!!!! __________________ "What's oppressive is letting your life be confined by old definitions of what everything is." -Zen Meister my_scatterheart YaHooka is.... Cannabis lovers from around the world pulling up a comfy chair, picking up a vaporizer, a bong, a brownie, a pipe, or a joint, getting high, stoned, buzzed or healthy. Uniting our minds in conversation...While Portraying a Positive Image of marijuana and marijuana users to the world. Treat your fellow YaHookans with kindness,respect and tolerance.

06-09-2011, 07:17 PM	#16 (permalink)
Mikey Seasoned YaHookan Join Date: Dec 2002 Location: gulf islands bc Posts: 7,443 Thanks: 1,144 Thanked 2,246 Times in 1,475 Posts	major ward __________________ RIP Gov

06-09-2011, 08:32 PM	#19 (permalink)
Mafoo nice daze Join Date: Nov 2005 Location: the anguish of anticipated transformation Posts: 5,975 Thanks: 3,776 Thanked 2,652 Times in 1,698 Posts	i think a big part of the problem was that i didnt know the stephan boltzman constant has units of watts/m^2k^4 i was using just watts/m^2 because i found some stupid webpage... anyway im still working on it, hopefully i can pop out a real answer. i left work early because its bugging me so much deadline is tomorrow, so its not too late, and im game to struggle with it. im not a physics major so its not likely ill be needing this in the future, though. ill start complaining more ferociously if i really cant get it __________________ PLUR* For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return

06-09-2011, 08:53 PM	#20 (permalink)
Mikey Seasoned YaHookan Join Date: Dec 2002 Location: gulf islands bc Posts: 7,443 Thanks: 1,144 Thanked 2,246 Times in 1,475 Posts	do a back flip! __________________ RIP Gov

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