Think you're smart?

[SuperGroove]

Here are some problems that are stumping me. Please help me out. Perty please? I need explanations too. My professor is gone this week and I'm not sure who to ask questions.

Coal is nearly pure carbon and is fairly dense. It has to be heated more to get it to start burning, but once it starts it gives off more heat than a similar size piece of wood. Determine whether the following statements are True or False reason for it.


A) It is easier to add oxygen to a coal fire, like they do in steel mills.
B) Coal radiates better while it is burning.
C) The coal has a lower activation energy than wood.
D) The carbon-carbon bonds that hold the coal together must be stronger than the carbon-hydrogen bonds that primarily are what hold wood together.
E) Coal does not have the air spaces of wood so it has more chemical bonds per cubic centimeter that can be broken to produce heat

The following statements are true or false. Mark them appropriately. Select T-True, F-False

A) When a car speeds up, the random motion of the atoms is converted into uniform motion of the car.
B) Heat is transferred by fast moving hot atoms bumping into slower ones and making them speed up.
C) If two objects are touching, heat flows from the colder object to the hotter object.
D) When the brakes slow a car down by friction, the brakes are quite hot. Therefore, the uniform motion of the car is reduced but the random motion of the atoms in the car is increased.
E) Colder atoms are moving more slowly than hotter ones.

 

[Narse]

tooooo much thinking for friday....... must not think

 

[greenfirs]

Nobody's going to do that huge assignment for you for a rinky dinky $5.

Try $25.

 

[GodBlessTheUSA]

I'll give it a shot at the first section. Too much to answer. Someone else can do the rest.

A) A rocket requires that its engines constantly apply a force to remain in orbit and to prevent falling.

No, the moon orbits the earth without addional force, as well as the thousands of pieces of space junk.

B) Astronauts in space appear to be weightless because there is no air pushing down on them.

No, the speed at which they are orbiting is as fast as the gravitational constant, so in essence, the rocket they are in is in a constant rate of falling.

C) The gravitational force between two masses, m1 and m2, depends upon the radius of the Earth.

Not sure, but it should depend more on mass and density than the radius.

D) If an orbiting space shuttle turns its rocket engines off, it will immediately begin plummeting towards the Earth.

False. Same as answer 1. The argument may be made that it will start to fall, but only because there is still some atmosphere where the shuttle orbits, and is brought down by atmospheric drag.

E) The best path for a rocket trying to reach orbit includes some horizontal component to the velocity.

True. If you shot it straight up, it would come straight back down, west of you accounting for the rotation of the earth.

 

[SuperGroove]

you don't have to answer them all. Sigh.

 

[Rallispec]

My educated guesses.. but i'm not actually postive on all of them

**edit, just realized in need explanations.. give me a few minutes to work on those **

false A) A rocket requires that its engines constantly apply a force to remain in orbit and to prevent falling.
false B) Astronauts in space appear to be weightless because there is no air pushing down on them.
false C) The gravitational force between two masses, m1 and m2, depends upon the radius of the Earth.
false D) If an orbiting space shuttle turns its rocket engines off, it will immediately begin plummeting towards the Earth.
true E) The best path for a rocket trying to reach orbit includes some horizontal component to the velocity.

List the possible options for pointing your rocket ship to get it into orbit around the earth in the order of how much rocket fuel the option would require. So the first choice would be the one that uses the least fuel, etc. with the last choice being the route that requires the most fuel. Put any routes that would not get you into orbit at the end.
i dont know these
? A) head straight up and stop when you get high enough
?B) head up angling towards the east from the beginning
?C) go straight up and once you are above the atmosphere go north
?D) go straight up and once you are above the atmosphere go west
?E) go straight up and once your are above the atmosphere go east


Coal is nearly pure carbon and is fairly dense. It has to be heated more to get it to start burning, but once it starts it gives off more heat than a similar size piece of wood. Determine whether the following statements are True or False reason for it.


true A) It is easier to add oxygen to a coal fire, like they do in steel mills.
true B) Coal radiates better while it is burning.
false C) The coal has a lower activation energy than wood.
dont know D) The carbon-carbon bonds that hold the coal together must be stronger than the carbon-hydrogen bonds that primarily are what hold wood together.
false E) Coal does not have the air spaces of wood so it has more chemical bonds per cubic centimeter that can be broken to produce heat

The following statements are true or false. Mark them appropriately. Select T-True, F-False

false A) When a car speeds up, the random motion of the atoms is converted into uniform motion of the car.
false B) Heat is transferred by fast moving hot atoms bumping into slower ones and making them speed up.
false C) If two objects are touching, heat flows from the colder object to the hotter object.
? D) When the brakes slow a car down by friction, the brakes are quite hot. Therefore, the uniform motion of the car is reduced but the random motion of the atoms in the car is increased.
true E) Colder atoms are moving more slowly than hotter ones.

List whether the following are True or False.

false A) Chemical potential energy is actually a form of random thermal energy.
false B) Heat flow actually refers to the increase of random thermal motion in a cold object due to contact with a hot object.
true C) Heat is not a special substance that flows from hot to cold objects.
false D) Cold atoms have less random thermal energy that do hot atoms. Therefore, surprisingly, a cup of boiling water has more thermal energy than the entire Artic Ocean.


okay, so i'm not a chemist or scientists or whatever, and most of those might be wrong. THose are my guesses though. if you ever find out the actualy right and wrong answers let us know.. i'd be interested in seeing how bad i did.

 

[SuperGroove]

rallispec,

Almost I got the same answers as you, but I too am only making educated guesses.

 

[SuperGroove]

bump?

 

[Demon-Xanth]

#1: EABCD
If you head up then head east, then you accelerate with the rotation of the earth and use the horizontal thrust w/o the drag of the air. Most very long range guns and missles are angled at 70-80 degrees to get the max distance possible. Heading due east from the start would use more fuel because of the drag from the atmosphere. Heading west would require you to effectively turn around using more fuel (direction is opposite to the earth's rotation). North would require you to effectively just accelerate to orbit speed.

 

[SuperGroove]

<< #1: EABCD
If you head up then head east, then you accelerate with the rotation of the earth and use the horizontal thrust w/o the drag of the air. Most very long range guns and missles are angled at 70-80 degrees to get the max distance possible. Heading due east from the start would use more fuel because of the drag from the atmosphere. Heading west would require you to effectively turn around using more fuel (direction is opposite to the earth's rotation). North would require you to effectively just accelerate to orbit speed. >>



E = going straight up and then going east

B = Going at an angle to the east

EABCD is not correct, and neither is BAECD. thanks though

 

[Rallispec]

list the possible options for pointing your rocket ship to get it into orbit around the earth in the order of how much rocket fuel the option would require. So the first choice would be the one that uses the least fuel, etc. with the last choice being the route that requires the most fuel. Put any routes that would not get you into orbit at the end.

A) head straight up and stop when you get high enough- this will work, uses the most fuel i think
B) head up angling towards the east from the beginning - dont think this will work, never get enough speed or momentum to break out of the earths gravity
C) go straight up and once you are above the atmosphere go north - should work, uses lots of fuel
D) go straight up and once you are above the atmosphere go west - will work, uses more fuel than going north though
E) go straight up and once your are above the atmosphere go east - im' pretty sure this is what the space shuttle actually does, so this would be my first choice.
e,c,d,a,b

Coal is nearly pure carbon and is fairly dense. It has to be heated more to get it to start burning, but once it starts it gives off more heat than a similar size piece of wood. Determine whether the following statements are True or False reason for it.


A) It is easier to add oxygen to a coal fire, like they do in steel mills.- Yes, oxegen will get the fire very hot very fast
B) Coal radiates better while it is burning. - well it doesnt radiate when its not burning, so i would assume true
C) The coal has a lower activation energy than wood. - yes, this is why it takes lighter fluid to get a charcoal fire started,.. the heat of a match alone will not catch them on fire, unlike with a peice of wood.
D) The carbon-carbon bonds that hold the coal together must be stronger than the carbon-hydrogen bonds that primarily are what hold wood together.false, i dont think they MUST... but i'm sure it helps
E) Coal does not have the air spaces of wood so it has more chemical bonds per cubic centimeter that can be broken to produce heat coal is denser than wood.. it has air spaces though. i would guess this to false

The following statements are true or false. Mark them appropriately. Select T-True, F-False

A) When a car speeds up, the random motion of the atoms is converted into uniform motion of the car. no, the atoms still have random motion, just with the added horizontal velocity vector produced by the car
B) Heat is transferred by fast moving hot atoms bumping into slower ones and making them speed up. or slow atoms slowing down fast atoms by bumping into them? i was say false
C) If two objects are touching, heat flows from the colder object to the hotter object. or heat flows from the cooler object to the hotter one. even a cold object has heat, the two objects try to equal to some sort of equalibrium. the hot gets cooler, the cooler gets hotter. i guess the answer would still be True though
D) When the brakes slow a car down by friction, the brakes are quite hot. Therefore, the uniform motion of the car is reduced but the random motion of the atoms in the car is increased. hot atoms and cold atoms have just as much random motion.. the hot ones just have more energy, do the random motion faster.. so i would say False
E) Colder atoms are moving more slowly than hotter ones. i think this is true....
hope htis helps

 

[Rallispec]

am i right?

 

[SuperGroove]

rallispec,

I will tell you what level my physics class is in a bit My answers mirrored yours.g ot em wrong.

 

[Rallispec]

okay cool.. I'm taking college physics I right now.. its pretty basic stuff like projectile motion and stuff like that. Nothing like random atomic movement or anything.. so mostly i've just been trying to make educated guesses. Do you have the right answers? I'd love to know them.. you've really got me thinking about this stuff now.

 

[SuperGroove]

I have answers for most of them, just not the three up top. We use CAPA, which is basically homework that allows multiple entries if you don't get the correct

I will have answers by Monday though. And not to make anyone feel bad, but myself, I am in the lowest Physics class, Physics 1010. It is for non scientists. Guess who teaches it, though? Carl Wieman, baby!! Bose-Einstein Condensate himself!

 

[Rallispec]

<< And not to make anyone feel bad, but myself, I am in the lowest Physics class, Physics 1010. It is for non scientists >>


haha.. dont worry.. like i said, i'm in intro physics also. Mine sounds a lot easier though, maybe we just havent gotten as far as you all yet. And i'm a computer scientist, not a real scientist.. well, a CS major.. not so much phsyics involved there. Anyways.. good luck in school, wish i could help more. And i dont think i've heard of your professor- should i have?
anyways... later
~rallispec

 

[SuperGroove]

Thanks for trying to help rallispec. You've got mail

 

[Demon-Xanth]

I'm fairly certain that my answer is correct with the only questionable one being where "B" lies. Try B at the end.

 

[DanFungus]

now I feel stupid... I only took Quantitative Physics last year...Chem. this coming summer...

 

[Bitek]

I'll try to help with a few, and I am a scientist, but that doesn't mean I'm neccesarily correct.


A) It is easier to add oxygen to a coal fire, like they do in steel mills. NO, the rate of the reaction,ie burning, will depend on the exposed surface area of the coal you mentioned coal is more dense, so O2 cannot easily penetrate in order to burn. I also know from history it took signifigant developments in furnace technology to effectively burn coal in favor of wood, (which was used before, but forests were quickly being consumed...)

B) Coal radiates better while it is burning. T, why coal furnances are hotter, can't burn as quick, or maybe stores more E before bonds break?..but can't give better explanation now, may be wrong
C) The coal has a lower activation energy than wood. F! It takes more E to break C-C bonds than C-H bonds, H-bonds are very weak, and are easily broken, see d
D) The carbon-carbon bonds that hold the coal together must be stronger than the carbon-hydrogen bonds that primarily are what hold wood together. T, wood is made primarily from cellulose, which is a polymer chain of glucose (sugar,) and is primarily held together by non-covalent hydrogen-bonds (not = to C-H bond, these are covalent but of lower E than C-C bonds)

E) Coal does not have the air spaces of wood so it has more chemical bonds per cubic centimeter that can be broken to produce heat this is a crappy question, really depends on the molec. structure of the material. Superficially it seems to be true, but there are many bonds in a single glucose molecule, so this may be a trick..., can't really be solved with the info provided (and info on densities of the materials?)

The following statements are true or false. Mark them appropriately. Select T-True, F-False

I'm much more of a chemist than a physist, so these are more of a guess..(im a molec. biologist)

A) When a car speeds up, the random motion of the atoms is converted into uniform motion of the car.?, T, maybe, more to this question than I know of the top of my head
B) Heat is transferred by fast moving hot atoms bumping into slower ones and making them speed up. T, I know there is an equation that relates temperature directly to kinetic motion of a molecule (is the definition of temperature)
C) If two objects are touching, heat flows from the colder object to the hotter object. not entirely based on the wording of the question, the NET flow of energy flows downhill, from higher energy objects to lower (laws of entropy and (2nd?) law of thermo.; you don't get cold touching a hot stove), but if they are asking if it is possible on an individual basis for a low E molecule to lose energy by colliding into a high E molecule than i would not be able to say I know that it is impossible
D) When the brakes slow a car down by friction, the brakes are quite hot. Therefore, the uniform motion of the car is reduced but the random motion of the atoms in the car is increased. Again, not up on this subject, but I would guess T
E) Colder atoms are moving more slowly than hotter ones. T see b, the absolute 0 is when molec. motion stops

hope this helps!

 

[SuperGroove]

thanks hafen, will let you know asap if you are correct