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supremespleen
12-02-2006, 09:54 PM
I need to construct some sort of object around a raw egg to prevent it from breaking.

Starting at a height of 1m and withstanding several drops until it is finally dropped from the bleachers in the football field.

The catch is, I can only use 5 sheets of computer paper and a meter of tape. Any ideas?

Bahamut
12-02-2006, 09:58 PM
Think of springs?

redchlorine
12-02-2006, 09:59 PM
Surround the egg with oragami boxes?

Kaiger
12-02-2006, 10:12 PM
Make a cone and put the egg inside. Although I think that'll only work once. Think crumple zones like a car hood.

damathacus
12-02-2006, 10:17 PM
To prevent the egg from breaking, you want to reduce the amount of force it experiences on impact. When the egg reaches the ground, it is going to stop, one way or another, and if it is stopped suddenly, by a large force, it will probably break in the process.

There are two ways to do this: Firstly, you can minimize the force necessary to stop the egg in the first place, by counteracting the accelerating force of gravity during the entire descent, i.e., a parachute.

Secondly, you can counteract the acceleration of the egg upon reaching the ground by applying a smaller force over a longer period of time, i.e., a cushioning effect. The momentum and energy the egg will gain from falling a particular distance will be the same, but rather than stopping the egg in a very short time with a large force, you can provide the same impulse and counteract the same momentum with a longer time spent decelerating and a smaller force applied over that time.

That's the difference between punching a pillow and punching a brick wall. The pillow gives, it lets your fist sink into it and decelerate at a lesser rate, rather than a brick wall that stops your fast in a fraction of a second with a much larger reactive force.

If you combine both of these ideas, you can not only slow the descent, but control it, as a parachute should assure that your contraption lands bottom-side down. If you can control which way your egg contraption will land, then you can place your egg at the top, and allow it to pass through several crash sheets of paper before hitting the ground.

I might try something like a long tube of paper, suspended from a paper parachute, with the egg taped to the top of the tube and shredded paper filling the tube to the brim. A tube just wide enough to fit the egg will provide additional resistance to slow it, besides making the most effective use of your limited materials, and if the tape is strong enough to suspend the tube while the whole apparatus is falling with a somewhat slowed descent, then it shouldn't break free from the tape until you actually hit ground, and at this point, the egg can slide into the tube and into all the shredded paper (I'm thinking anywhere from half a metre to a metre long), which ought to be enough to slow it down without braeking it from any height.

Red Shadow
12-02-2006, 10:17 PM
i remember doing this in eighth grade and being the only person to get an a

we used milk cartons, and i filled mine with oil

for some reason im thinking maybe constructing a gyroscope shaped thing with the tape and paper and suspending the egg in the middle would be pretty good

CE
12-02-2006, 10:22 PM
wtf

we need to have homework like this in physics

Bahamut
12-02-2006, 10:44 PM
Just a note, I remember doing something similar in middle school - the parachute idea does not work well because it is such a short height - you need a large height in order for the parachute to be effective.

Kitsuta
12-02-2006, 11:00 PM
I need to construct some sort of object around a raw egg to prevent it from breaking.

Starting at a height of 1m and withstanding several drops until it is finally dropped from the bleachers in the football field.

The catch is, I can only use 5 sheets of computer paper and a meter of tape. Any ideas?

I know nothing about physics so I'm just making this up.

Tape two sheets of the computer paper together lengthwise, SECURELY(no air in between, use one piece of thick tape along the entire edge).

Tape another two sheets together on top of each other, only use tape that is rolled onto itself in a wide circle that you can stick your hand through. Use several of these makeshift double sided tape to tape the two pieces of paper together. Finally, do the same thing with the last piece of paper and the egg, and tape the long makeshift piece of paper to the two insulated pieces of paper, and tape it all to the little paper package around the egg.

I have NO idea how much tape that would use, though.

EDIT: Bahamut has a good point.

Paratha
12-02-2006, 11:12 PM
I remember some guy accomplishing this by noting that, in our assignment prompt, it was never stated that the egg needed to be in freefall.

So he just taped the egg to a long and narrow length of paper, and manually lowered the paper along with the egg. So my advice is, check the exact wording of the assignment.

damathacus
12-02-2006, 11:27 PM
I remember some guy accomplishing this by noting that, in our assignment prompt, it was never stated that the egg needed to be in freefall.

So he just taped the egg to a long and narrow length of paper, and manually lowered the paper along with the egg. So my advice is, check the exact wording of the assignment.

There's a future lawyer, but not an engineer or physicist.

Re: the parachute. I've never done this or seen it done, although of course I've heard of the infamous egg-drop before. I was thinking ahead to the drop off the gym bleachers. It seems that the parachute ought to slow it down a little, but more important is assuring that the contraption lands right-side-up when you drop it from a greater height. Otherwise you have to account for the possibility of impact occuring from any side, and with the limited materials, that makes this a major challenge.

How would you do it Bahamut?

Bahamut
12-02-2006, 11:38 PM
Not sure, but the parachute comment was just a note - if one was to observe the differential equation, you would hardly shorten the velocity given the time frame the object is in air. I also remember when I did a similar assignment that parachutes were useless and were just laughable to watch in their futility.

So yeah, I would think of trying to cushion the egg and secure it.

Kaiger
12-02-2006, 11:57 PM
Figured I'd at least post a picture of what I was talking about.
http://img369.imageshack.us/img369/6893/eggdropuq8.jpg

The placement of the egg towards the front of the cone pretty well ensures it will fall tip first. On impact the energy is dissipated by the crupling of the nose, which basically acts like a spring. Or at least that's my take on it, I'm not a mechanical engineer though...

damathacus
12-03-2006, 12:38 AM
Figured I'd at least post a picture of what I was talking about.
http://img369.imageshack.us/img369/6893/eggdropuq8.jpg

The placement of the egg towards the front of the cone pretty well ensures it will fall tip first. On impact the energy is dissipated by the crupling of the nose, which basically acts like a spring. Or at least that's my take on it, I'm not a mechanical engineer though...

I think you're onto something there. You could also pre-fold the lower half of the cone so that it would be more pre-disposed to crumple, depending on how stiff the material was to begin with. Given that it's computer paper, that may not be necessary, but since there are several sheets, maybe it would be.

We don't want the cone to stop dead and the egg to crack while trying to keep moving and squeeze through the tapering tunnel. The crumpling is crucial.

JohnderriLLL
12-03-2006, 12:47 AM
we got to do model rockets and solar powered cars in our class.

Bahamut
12-03-2006, 12:57 AM
Figured I'd at least post a picture of what I was talking about.
http://img369.imageshack.us/img369/6893/eggdropuq8.jpg

The placement of the egg towards the front of the cone pretty well ensures it will fall tip first. On impact the energy is dissipated by the crupling of the nose, which basically acts like a spring. Or at least that's my take on it, I'm not a mechanical engineer though...

I think you're onto something there. You could also pre-fold the lower half of the cone so that it would be more pre-disposed to crumple, depending on how stiff the material was to begin with. Given that it's computer paper, that may not be necessary, but since there are several sheets, maybe it would be.

We don't want the cone to stop dead and the egg to crack while trying to keep moving and squeeze through the tapering tunnel. The crumpling is crucial.

Or even better, stuff the bottom of the cone with paper.

Kaiger
12-03-2006, 01:24 AM
Probably the best thing to do at this point is to build some of these different ideas and see what happens. Plus I agree that the parachute idea is a bad one from both the diff. eqn. and from my experience in 5th grade at "Astro Camp" :( .

Edit: Gotta be careful about stuffing stuff in the nose. If the nose is either too stiff or not stiff enough it won't dissipate enough energy. Stuffing the nose would have a similar effect to making it stiffer, which could put you past the sweet spot. Similarly it could put you into the sweet spot. At this point you've just got to try stuff.

JohnderriLLL
12-03-2006, 01:37 AM
when u stuff the paper in the bottom of the cone do not pack it tight. its a cushion, that means precrumple then uncrumple the paper.

damathacus
12-03-2006, 01:40 AM
Figured I'd at least post a picture of what I was talking about.
http://img369.imageshack.us/img369/6893/eggdropuq8.jpg

The placement of the egg towards the front of the cone pretty well ensures it will fall tip first. On impact the energy is dissipated by the crupling of the nose, which basically acts like a spring. Or at least that's my take on it, I'm not a mechanical engineer though...

I think you're onto something there. You could also pre-fold the lower half of the cone so that it would be more pre-disposed to crumple, depending on how stiff the material was to begin with. Given that it's computer paper, that may not be necessary, but since there are several sheets, maybe it would be.

We don't want the cone to stop dead and the egg to crack while trying to keep moving and squeeze through the tapering tunnel. The crumpling is crucial.

Or even better, stuff the bottom of the cone with paper.

But if you use a cone, the egg will only be able to fall so far before it'll be squeezed too much. If you put the egg higher up, the centre of mass will likely cause the cone to flip over upside down. For that reason, I prefer the crumple-zone idea. You make better use of the full stopping distance.

Gollgagh
12-03-2006, 01:41 AM
I seriously doubt that there'd be that much sideways pressure on the egg from the cone, but what do I know? I'm a chemistry major.

Bahamut
12-03-2006, 01:45 AM
So maybe the egg should be taped tightly to the bottom of the cone also?

Red Shadow
12-03-2006, 01:55 AM
my little pseudo-gyroscope idea, by the way, has "roll cage" in mind

supremespleen
12-03-2006, 02:36 AM
Parachutes not allowed. I had thought of a cone as well, but it needs to last through several drops.

I thought of making one with little paper protrusions all along the outside kind of making it look like a spiked ball.

Don't think the paper would be strong enough to make it work though.

Crazyonr1
12-03-2006, 03:04 AM
Could you do two differnt cones, and use the tape to suspend the egg between the halves? That way, no matter which side it was on, it would have the same amount of crumple zone

supremespleen
12-03-2006, 03:14 AM
My dad had a good idea - make a sort of sphere around the egg, supported by pillars from the egg to the sphere.

shadownova
12-03-2006, 03:24 AM
what i would do is create a triangle pyramid of the ballon oragami with the egg being in the certer one, that way you have air cushions on all sides regardless of how it dropped, id put a pic up but i hate my photoshop skills

Bahamut
12-03-2006, 03:35 AM
My dad had a good idea - make a sort of sphere around the egg, supported by pillars from the egg to the sphere.

The problem is that they won't stop the acceleration of the egg once the sphere hits the ground - the sphere will collapse due to the flimsiness of the paper.

supremespleen
12-03-2006, 03:42 AM
what i would do is create a triangle pyramid of the ballon oragami with the egg being in the certer one, that way you have air cushions on all sides regardless of how it dropped, id put a pic up but i hate my photoshop skillsBalloon origami?

Red Shadow
12-03-2006, 03:46 AM
i cant believe i still remember how to make those

Kaiger
12-03-2006, 04:45 AM
Parachutes not allowed. I had thought of a cone as well, but it needs to last through several drops.

I thought of making one with little paper protrusions all along the outside kind of making it look like a spiked ball.

Don't think the paper would be strong enough to make it work though.

Can't use the five sheets of paper to make five cones and just hope that you only get tested on five drops?

I just can't see anything made of paper being reused that way. Even if you make shredded paper padding, after each drop it'll pad less and less.

I seriously doubt that there'd be that much sideways pressure on the egg from the cone, but what do I know? I'm a chemistry major.

I think the paper/tape would break before the egg anyways. I mean, have you made an omlette? Those little guys are tough!

Dunnowhathuh
12-03-2006, 05:59 AM
Bah, all I did in high school physics was light up a few lights and wave a few ropes around. The cone idea is a good start but as mentioned, the thing has to be dropped multiple times (presumably without modification between drops). Stuffing the tip with paper as Bahamut mentioned may work but as Kaiger said, it might make the structure more solid. Using shredded paper instead won't work for the second drop because the initial drop would have compressed the whole tip into a brick wall basically. Having 5 individual cones for each test wouldn't work either because the crumpling effect would be severely reduced if the tip isn't properly reinforced.

If you can at least touch your design after every drop, you could panel beat the design back into shape. Yeh, the external structure would be weakened but if you had shredded paper reinforcing the tip of the cone, you could get those back into a loose mess instead of a brick wall.

Playing around with air pressure with only 5 sheets of paper and some tape won't work too well either (you could give the damn thing wings if you weren't limited). A parachute wouldn't work at 1m, not enough air resistance so don't even consider that idea (you're not allowed to anyway, so it doesn't matter).

No chance you could tamper with the egg eh? Soaking the whole thing in vinegar would do wonders...or enchance the exploding effect when it hits the floor. Too bad you can't turn normal paper into bubble wrap either. If only Macgyver were part of the OCR forums, he'd save your egg with bits of shoelace and some fluff off the back of your shirt.

supremespleen
12-03-2006, 06:06 AM
I can touch the design after each drop.

Hmph. I will have to sleep on this.

Zero_Infiniti
12-03-2006, 06:15 AM
protest, egg drops are inhumane against unborn chickens. or tell them you're religion forbids it. they'll have to give you an 'a'

or say screw it and roll the egg in a paper, and chuck it at someone you really dislike. followed by 'damn, i guess my design didn't work'

supremespleen
12-03-2006, 06:21 AM
protest, egg drops are inhumane against unborn chickens. or tell them you're religion forbids it. they'll have to give you an 'a'

or say screw it and roll the egg in a paper, and chuck it at someone you really dislike. followed by 'damn, i guess my design didn't work'I kind of need an A.

Without any funny business!

shadownova
12-03-2006, 06:29 AM
i believe the balloons are also called waterbombs

http://www.things2make.com/Things2make_files/Instructions%20over%205/waterbombs.htm[/img]

just blow up the bombs and don't add water, itll be like an air cushion, make 5, put the egg in the center and tape the others so that it looks like a 3 sided pyramid, that way, any way it falls it has support, not sure if the phsyics will work out, but it has been 5 years since i took that course

KWarp
12-03-2006, 06:40 AM
I have a simple idea. Make something like a paper cube, but angle the vertical sides a little bit outwards so they give in slightly when the egg lands on it.

Back_Lit
12-03-2006, 06:45 AM
I have a physics question too actually.

A 200 gram piece of metal is 30 degrees Celsius and is put into a beaker of boiling water, how much heat energy does the metal absorb?

Hawkwing
12-03-2006, 06:58 AM
Oh i did this and won the competition at my school

you make a big cylinder, make a coen and put it titled in the cylinder

make little cylinders aaround the side for stabalization and then cut the rest of your paper into shreds and put it between the cone and the cylinder and some inside the cone too


works like a charm

JohnderriLLL
12-03-2006, 07:01 AM
boil the egg?

revenge_of_quatermass
12-03-2006, 07:26 AM
Black_Lit

This is for the metal question. I'm pretty sure that it depends on how length of time it's in there, its material properties and it's dimensions. However looking through my old heat transfer book I found that for a convective heat transfer which is what you have, the genral formula would be something like this q"=h(Ts-Tinfinity). q" is the heat flux transfered into the body, h is the convective heat transfer coefficient, Ts is the surface temperature of the object, and Tinfinity is the temperature of the fluid that its placed into. Normally the convective heat transfer coefficient is a bitch to calculate, but for a boiling fluid, this value can range between 2,500 and 10,000. Basically you'll have to estimate this value. I don't know if this is way too much, or if this is what you're looking for. If anybody can see a simpler way, be my guest. Peace.

damathacus
12-03-2006, 03:05 PM
I have a physics question too actually.

A 200 gram piece of metal is 30 degrees Celsius and is put into a beaker of boiling water, how much heat energy does the metal absorb?

If the metal is left in there until equilibrium is reached, the metal and water will eventually be the same temperature. In other words, you set up two equations, one for the metal with the initial temperature at 30, and the final temperature being what you want to calculate, and the water with an initial temperature at 100, and the final temperature being the same value.

You can manipulate the equations so that you are trying to calculate the final temperature for each, then set them equal to each other. I'm guessing the only unknown in the equation will be the change in heat energy on each side. Since the energy will be lost in one equation and gained on the other, you probably will be able to move them both to the same side of the equation and end up with 2 times the unknown energy, divide both sides by two, and sort out what the heat transfer is from the masses of metal and water and the specific heats and initial temperatures of both substances.

I'm doing this without actually seeing the equations in front of me, but I'm betting that's it.

There could also potentially be a twist. If the water is boiling, some of the water in an enclosed beaker could potentially be steam. Steam at the same temperature as water has higher thermal energy, because energy is required to make a phase change from liquid to gas state. In that case you'd have to take into account the proportion of water that is steam and add that energy in to your equation.

revenge_of_quatermass
12-03-2006, 03:46 PM
I have a physics question too actually.

A 200 gram piece of metal is 30 degrees Celsius and is put into a beaker of boiling water, how much heat energy does the metal absorb?

If the metal is left in there until equilibrium is reached, the metal and water will eventually be the same temperature. In other words, you set up two equations, one for the metal with the initial temperature at 30, and the final temperature being what you want to calculate, and the water with an initial temperature at 100, and the final temperature being the same value.

You can manipulate the equations so that you are trying to calculate the final temperature for each, then set them equal to each other. I'm guessing the only unknown in the equation will be the change in heat energy on each side. Since the energy will be lost in one equation and gained on the other, you probably will be able to move them both to the same side of the equation and end up with 2 times the unknown energy, divide both sides by two, and sort out what the heat transfer is from the masses of metal and water and the specific heats and initial temperatures of both substances.

I'm doing this without actually seeing the equations in front of me, but I'm betting that's it.

There could also potentially be a twist. If the water is boiling, some of the water in an enclosed beaker could potentially be steam. Steam at the same temperature as water has higher thermal energy, because energy is required to make a phase change from liquid to gas state. In that case you'd have to take into account the proportion of water that is steam and add that energy in to your equation.

If there's steam in the beaker, it can't transfer to the piece of metal. If the steam isn't in contact with the metal, there's no means for a heat transfer to occur. If the metal was half submerged, you would have to worry about it.

supremespleen
12-03-2006, 04:03 PM
My dad just had a sweet idea. I will post pics later.

damathacus
12-03-2006, 04:15 PM
I have a physics question too actually.

A 200 gram piece of metal is 30 degrees Celsius and is put into a beaker of boiling water, how much heat energy does the metal absorb?

If the metal is left in there until equilibrium is reached, the metal and water will eventually be the same temperature. In other words, you set up two equations, one for the metal with the initial temperature at 30, and the final temperature being what you want to calculate, and the water with an initial temperature at 100, and the final temperature being the same value.

You can manipulate the equations so that you are trying to calculate the final temperature for each, then set them equal to each other. I'm guessing the only unknown in the equation will be the change in heat energy on each side. Since the energy will be lost in one equation and gained on the other, you probably will be able to move them both to the same side of the equation and end up with 2 times the unknown energy, divide both sides by two, and sort out what the heat transfer is from the masses of metal and water and the specific heats and initial temperatures of both substances.

I'm doing this without actually seeing the equations in front of me, but I'm betting that's it.

There could also potentially be a twist. If the water is boiling, some of the water in an enclosed beaker could potentially be steam. Steam at the same temperature as water has higher thermal energy, because energy is required to make a phase change from liquid to gas state. In that case you'd have to take into account the proportion of water that is steam and add that energy in to your equation.

If there's steam in the beaker, it can't transfer to the piece of metal. If the steam isn't in contact with the metal, there's no means for a heat transfer to occur. If the metal was half submerged, you would have to worry about it.

If the system is closed, the steam-water mixture will have to turn fully to water before the heat transfer to the metal will allow the temperature to start decreasing. If the problem is one of equilibrium, you can't end up with non-boiling water and steam in the same closed system at equilibrium.

The original poster was nowhere near specific enough on the terms of the question to settle exactly what we are trying to solve and under what conditions, however. Details are important in physics. You can't half-tell someone about a question and don't tell them all your information or the actual wording of what is being asked and expect to get a single, straightforward answer. Maybe it's heat transferred after a period of time, in which case you were probably on the right track, maybe it's heat transfer after equilibrium has been reached, in which case I was probably on the right track. Original poster, are you following this, or what?

revenge_of_quatermass
12-03-2006, 04:29 PM
I have a physics question too actually.

A 200 gram piece of metal is 30 degrees Celsius and is put into a beaker of boiling water, how much heat energy does the metal absorb?

If the metal is left in there until equilibrium is reached, the metal and water will eventually be the same temperature. In other words, you set up two equations, one for the metal with the initial temperature at 30, and the final temperature being what you want to calculate, and the water with an initial temperature at 100, and the final temperature being the same value.

You can manipulate the equations so that you are trying to calculate the final temperature for each, then set them equal to each other. I'm guessing the only unknown in the equation will be the change in heat energy on each side. Since the energy will be lost in one equation and gained on the other, you probably will be able to move them both to the same side of the equation and end up with 2 times the unknown energy, divide both sides by two, and sort out what the heat transfer is from the masses of metal and water and the specific heats and initial temperatures of both substances.

I'm doing this without actually seeing the equations in front of me, but I'm betting that's it.

There could also potentially be a twist. If the water is boiling, some of the water in an enclosed beaker could potentially be steam. Steam at the same temperature as water has higher thermal energy, because energy is required to make a phase change from liquid to gas state. In that case you'd have to take into account the proportion of water that is steam and add that energy in to your equation.

If there's steam in the beaker, it can't transfer to the piece of metal. If the steam isn't in contact with the metal, there's no means for a heat transfer to occur. If the metal was half submerged, you would have to worry about it.

If the system is closed, the steam-water mixture will have to turn fully to water before the heat transfer to the metal will allow the temperature to start decreasing. If the problem is one of equilibrium, you can't end up with non-boiling water and steam in the same closed system at equilibrium.

The original poster was nowhere near specific enough on the terms of the question to settle exactly what we are trying to solve and under what conditions, however. Details are important in physics. You can't half-tell someone about a question and don't tell them all your information or the actual wording of what is being asked and expect to get a single, straightforward answer. Maybe it's heat transferred after a period of time, in which case you were probably on the right track, maybe it's heat transfer after equilibrium has been reached, in which case I was probably on the right track. Original poster, are you following this, or what?

Agreed, more information is required, like we don't know if this is silver or a chunk of lead.

supremespleen
12-03-2006, 06:31 PM
We did it.

Back_Lit
12-03-2006, 06:44 PM
Sorry about not having enough info to solve the problem, I was posting by memory =/

So here is the EXACT problem, though it still doesn't help from my perspective.

A 250 gram glass marble is taken from a freezer at -23 degrees C and placed into a beaker of boiling water [just consider it as 100 C]. How much thermal energy is absorbed by the marble?

I don't have a clue how to solve this, we never did one in class or lab lack this. The ones we did gave us the mass of the water. Anyone have a clue? (I don't think I need the mass of the water though).

atmuh
12-03-2006, 06:52 PM
is that q = m * c * (T2 - T1) ?

Bahamut
12-03-2006, 06:58 PM
is that q = m * c * (T2 - T1) ?

Problem is, you don't know the final temperature, and to solve it using that equation would require you to know the mass of the water.

Magewout
12-03-2006, 07:32 PM
*woot first post :O*

The m needed would be the marble's weight, 0.250 kg. Also, the you can assume that if the water keeps boiling, the final temperature of the marble will be 100 degrees C.

Q = m[marble] . c[marble] . (100 - T[marble])

m[marble] = 0.250 kg
c[marble] would be = c[glass] (look that one up)
T[marble] = -23 C

jontilton
12-03-2006, 08:15 PM
Does anyone want to help me with my physics????

Early skeptics of the idea of a rotating Earth said that the fast spin of Earth would throw people at the equator into space. The radius of Earth is about 6400 km. Show why this objection is wrong by calculating:

A) the speed of a 97 kg man at the equator;
B) The force acting on him to accelerate him in a circle around the Earth
C) The weight of the man;
D) How much force is holding him to the surface of the Earth

I'm so confused... much thanks for any help :-)

Paratha
12-03-2006, 08:40 PM
A) v = 2*pi*R/T

R = Radius of Earth, 6400 km.
T: T is the period of rotation, i.e. one day. One day = 24 hours. I don't think it's necessary to convert from hours to seconds, since km/h seems like a good unit to stick with.

v = 1675.52 km/h

Now you have v.

B) F = ma.

a = centripetal acceleration = v^2/r

a = 438.649 km/h^2
F = 42549 km*kg/h^2 (or 3.28 N (kg*m/s^2), if you prefer)

C) Weight = mg. Since gravity is 9.81 meter/second^2, convert this to km/h^2. (g = 127138 km/h^2)

W = 1.233 * 10^7 km*kg/h^2 (or 951.57 N)

D) W - F = a positive number. Therefore, I am at my computer, and not hurtling towards the atmosphere, about to be burnt up.

Oh, and Back_Lit, though Magewout's solution is correct, when finding C, make sure you find the specific heat (J/g*Celsius), and not the heat capacity (J/Celsius).

Magewout
12-03-2006, 08:42 PM
Don't know if I'm totally correct...

1) I'd say the speed of a man at the equator would be (2 . pi . 6400 km) / 24h , seeing as the earth turns around in 24 hours.

2) This is a long time ago... with the speed you've just calculated, the radius, and his weight, you would be able to calculate that force

3) The weight of the man would be 97 kg . 9.81 N/kg

4) The force holding him to the surface would be gravity, so Fz = m . g . h = 97 kg . 9.81 N/kg . 6400 km

Back_Lit
12-03-2006, 10:27 PM
*woot first post :O*

The m needed would be the marble's weight, 0.250 kg. Also, the you can assume that if the water keeps boiling, the final temperature of the marble will be 100 degrees C.

Q = m[marble] . c[marble] . (100 - T[marble])

m[marble] = 0.250 kg
c[marble] would be = c[glass] (look that one up)
T[marble] = -23 C

8O Now I can finish my damn HW for physics AND get 8 hrs sleep. Thanks a lot!

jontilton
12-03-2006, 10:45 PM
oh good thanks. i had figured out part A and then i was lost on all of the rest ;-)

Bahamut
12-03-2006, 10:49 PM
I was wondering whether you can assume the final temperature would be 100 degrees C...should've posted my thought on that. That's a poor question IMO though.

As for the rotating Earth problem:

A) Note that the period of rotation = 24 hours = 24 * 60 seconds. use v = Circumference of the Earth / T (circumference = 2 * pi * r)

B) Use that the centripetal force = v^2/r

C) W = m * g

D) W - m * v^2/r

Old Man Time
12-03-2006, 11:09 PM
We did it.

Care to elaborate?

Thin Crust
12-03-2006, 11:13 PM
can someone tell me how to put pictures in my signature? The copy paste feature doesn't seem to work on this level and thats the only thing that i can think of.

Old Man Time
12-03-2006, 11:17 PM
can someone tell me how to put pictures in my signature? The copy paste feature doesn't seem to work on this level and thats the only thing that i can think of.

http://www.ocremix.org/phpBB2/viewtopic.php?t=11654&start=0

I would explain it myself, but that should make it easier.

If you want a sig made, ask here (http://www.ocremix.org/phpBB2/viewtopic.php?t=41441&start=0).

Hopefully that answers your question, just post in the help/newbies section next time instead of a random thread :wink:

EDIT: I like the sig.

linkspast
12-20-2006, 06:11 AM
We did it.

Care to elaborate?

Yes plz I just read this thread and now I feel entitled to see some results.

supremespleen
12-23-2006, 04:15 AM
We did it.

Care to elaborate?

Yes plz I just read this thread and now I feel entitled to see some results.Oh sorry. If I remember I'll take webcam pics of it tomorrow morning.