Basic science questions any HS graduate should know the answer to - SFN Version

[timo]

@Atheist: Like the questions' date=' common sence yet scentific. Would they need to know the reasoning behind them for the answers though do you think?[/quote']

Yes, people should know the reason behind it. But as a matter of fact, the first two questions are explicitely chosen such that the actual physics knowledge is absolutely minimal. E.g. knowing that running a fridge consumes energy, that the energy has to go somewhere and that it will do so as heat is sufficient for question 1. No need to know more thermodynamics other than that heat is a form of energy.

[RyanJ]

Yes, people should know the reason behind it. But as a matter of fact, the first two questions are explicitely chosen such that the actual physics knowledge is absolutely minimal. E.g. knowing that running a fridge consumes energy, that the energy has to go somewhere and that it will do so as heat is sufficient for question 1. No need to know more thermodynamics other than that heat is a form of energy.

 

OK, great that means they are perfect for the list then... this poll is going to be quite big I think...

 

Heres another one:

 

When food is swallowed is it simply pulled down by gravity or by other means. Explain answer.

 

A lot of people had that one wrong as I remember...

 

Cheers,

 

Ryan Jones

[timo]

... A lot of people had that one wrong as I remember...

Whether anatomical details like the muscles swallowing the food are something that you should really know after high school (and the question whether it´s a detail or basics) should be for others to decide. But keep in mind that if I understood the purpose of the questions correctly, it´s not about tricking people but about giving at hand a checklist to test very basic knowledge which everyone should have.

[the tree]

Here goes one (although it´s pretty popular so many people will already know the answer):

In a TV show' date=' there´s three closed doors. Behind one, there´s a prize, behind the others, there´s nothing. As the candidate, you may chose a door and grab whatever is behind it. After having chosen a door, the moderator will open a door behind which is nothing - regardless whether your choice was the prize or not. You are then allowed to rethink your decision and chose the other remaining door:

a) Yeah, that sounds like a good idea.

b) "No way, my chances of winning are better if I stick with my original decision"

c) Who cares? The chances of winning the prize are the same for both remaining doors.[/quote']Aren't 'a' and 'c' equally good awnsers?

[5614]

Mmmm, I don't think that kind of detail about the intestine is really required for high school students.

 

I'd rather have them knowing the basics, fundementals and laws of science rather than a specific detail about the intestine which is quite likely they will never need to know anything about.

 

the tree: I suppose what Atheist was getting at was that if you said A then you would be implying that your choice is more likely to be correct, which it is not.

[RyanJ]

Whether anatomical details like the muscles swallowing the food are something that you should really know after high school (and the question whether it´s a detail or basics) should be for others to decide. But keep in mind that if I understood the purpose of the questions correctly, it´s not about tricking people but about giving at hand a checklist to test very basic knowledge which everyone should have.

 

I'm not shure but I believe I knew that swallowing was not a direct result of gravity alone in highschool. You are right however the questions should test very basic knowledge and on that front I am not shure this counts so...

 

Cheers,

 

Ryan Jones

[timo]

I'm not shure but I believe I knew that swallowing was not a direct result of gravity alone in highschool.

You´re right. That´s effectively what I said, in case you didn´t correctly understand me. Swallowing is done by some muscles in your throat. You can simply test that by swallowing something with your head down.

 

 

I suppose what Atheist was getting at was that if you said A then you would be implying that your choice is more likely to be correct, which it is not.

Let me say this in advance: The question was not in my original list. It´s just that someone asked for a statistical question and this one was the first one that came to my mind. For the answer: You´d better sit down and calculate the result rather than to rely on your intuition. Intuition often is a certain way to get statistical questions wrong. To some extend that in fact is something that someone who has a basic education in math should know.

[s pepperchin]

I would say that people should have a basic understanding of science, however I think that as people who are scientist it seems kind of elitist to tell people they need to know organic chemistry, nuclear physics, cosmology or any specialized area of science. I don't know enough about art to be a master painter and I don't expect a master painter to know enough about physics to do quantum mechanics.

[Prime-Evil]

If all the mass were to be confined to a smaller radius' date=' it would cause the [i']weight[/i] to be higher because the average distance between all the mass and you would be less. If compressed far enough, past the Schwarzschild radius, it would become a black hole. So yes, the weight would increase if the distance was lowered. The mass would stay the same.

Think about mass on the other side of the earth from you, it exerts less gravity on you than the earth below your toes. If you brought all the mass as close to you as possible, your weight would increase. Don't think of the earth as one object, think of it as trillions and trillions of atoms.

If all the mass was at the core and you were somehow suspended where the old radius was it would still be higher. All the gravity would pull down whereas before some pulled at an angle (mass close to surface 1/4 of the way around earth in either way.)

That wasn't exactly my question was it? My question was what if you changed the distribution of the Earth's mass but kept your distance from the Earth's center of gravity constant.

[s pepperchin]

That wasn't exactly my question was it? My question was what if you changed the distribution of the Earth's mass but kept your distance from the Earth's center of gravity constant.

 

 

If that is the case then there would be no difference.

[Prime-Evil]

If that is the case then there would be no difference.

That's what I have been told, but I haven't quite figured it out.

 

If you use the simple formula, and a mid-latitude radius, and neglect the small stuff like rotation, time of day, and tides, then it seems to work out pretty close to 1 kg weighing 9.81N.

 

F = G m1 m2 / r^2

 

G = 6.6742E-11 [N.m^2/kg^2]

m1 = 1 [kg]

m2 = 5.9742 x 10^24 [kg]

 

r = 6,371,000 [m], F = 9.823 [N]

r = 6,375,000 [m], F = 9.811 [N]

r = 6,378,000 [m], F = 9.802 [N]

 

Pretty close eh? So I suppose it doesn't prove much.

 

But why doesn't all that mass out to the sides cause of weight to be reduced? I suppose it is countered by some of the mass directly beneath us being closer and some of it being farther away and the fact that r is squared, not linear. Has anyone seen an actual proof of this?

 

Is this what the estimate of the Earth's mass is based upon?

 

When I changed the mass of the earth into 6 or more descrete masses it did seem to make a difference, so I'm thinking whatever you do does have to approximate a sphere maybe. Can anyone help me out on this? Time to break out the old calculus maybe, or just use more discrete blobs and approach a sphere and use brute force and shear ignorance, which is sort of what calculus is anyway.

[Prime-Evil]

Here they estimate the Earth mass, but don't discuss effect of distributed mass of Earth:

http://www.wonderquest.com/calculation-mass-of-earth.htm

 

So I think I have to go straight to the source, Sir Isacc's Law of Gravity, and see where he says that the distribution of mass doesn't matter unless you become surrounded, i.e, dig towards center of earth.

 

But here it only talks about a binary system without discussing distribution of mass. I need to see where Newton broke out his calculus. I presume he took care of this somewhere along the way, and that it was either one of the more bring bits, to him anyways.

http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html

 

Aha. Now I see. Newton's hollow earth paradox. Two cones.

So he did manage to get the job done without calculus after all.

http://www-spof.gsfc.nasa.gov/stargaze/StarFAQ2.htm#q29

[Prime-Evil]

As for what gravity is, I am not sure. I can only suspect that it is one of those things that itself defines both space and time, and is itself defined by them.

[JustStuit]

That wasn't exactly my question was it? My question was what if you changed the distribution of the Earth's mass but kept your distance from the Earth's center of gravity constant.

Oh. I think it still would be different. If the earth was hollow with all the mass on the outside and you were on the top of it somewhere, it would be less then if the mass was equally distributed. This is because some of the mass would pull at an angle, having less effect on you than the mass pulling straight down. If it was all in one point at the center and you were in the same place, all the mass would pull down.

[Bignose]

A great test of basic statistical knowledge (adapted from radio-doc Dr. Dean Edell):

 

A recent (made-up) study shows that you can reduce your chances of colon cancer by one-third if you eat 30 carrots a day. If the general populations' chances of getting colon cancer are only 0.02 %, if you ate 30 carrots a day (which is a heck of a lot of carrots), what are your new chances of getting colon cancer? If a different study showed that drinking 1 soda a day doubled your chances of colon cancer, how many soda drinkers would it take to statisitcally expect at least 1 colon cancer sufferer, i.e. on average, 1 in x soda drinkers will have cancer. Are the odds better or worse for the soda drinker that eats 30 carrots, or the person who does neither?

 

Dr. Edell uses examples like this all the time to 1) show that studies often give conflicting advice... just look at the history of studies on coffee. and 2) shows that typically, the percentages are so small in the first place, that even if something is bad for you in one way, so long as it is in moderation, there is really no harm. For example, if drinking coffee doubles your chances of brain cancer... well, the chances of brain cancer are probably 1 in 10's if not 100's of thousands. 'Doubling' the chances sure sounds scary when heard on the evening news, but going from 1 in 200,000 to 1 in 100,000 doesn't look so bad. Looks even better if you write 0.0005% to 0.001%. That coffee that some people absolutely love is probably among the least important things to worry about. Same thing if eating something you don't like, like carrots, or fish... sure, it may reduce your chances a little, but what were the chances in the first place? Life is too short to fill it doing things you may hate just for the tiniest of chances of living longer so you have more time to do more of the things you may hate. This is not to say don't eat healthy, etc., but at the same time don't obsess.

[Prime-Evil]

Oh. I think it still would be different. If the earth was hollow with all the mass on the outside and you were on the top of it somewhere, it would be less then if the mass was equally distributed. This is because some of the mass would pull at an angle, having less effect on you than the mass pulling straight down. If it was all in one point at the center and you were in the same place, all the mass would pull down.

That is what I always thought, or at least for the last 25 years or so. I think someone may have mentioned something somewhere along the way about hollow spheres and so forth, but I am nit sure if I paid attention to the bit about double cones. So you are basically where I was at up until a few minutes ago, which ain't much compared to the life of the universe.

 

It is probably best to start on the inside of this hollow sphere. Consider two very narrow cones spreading out in opposite directions from anywhere within the sphere. The gravitational attraction in both directions will be the same because the area, and thus shell volume, and thus mass, increases with the square of the distance while the force reduces with square of the distance. So there is no net gravitational field at all within the hollow sphere. Wierd huh. A solid sphere is of course a set of concentric hollow spheres, and so the only net gravity inside the earth is from the solid sphere you are standing on, and the hollow spheres outside of this cancel themselves out. OK, I guess that still leaves the orginal problem of the sphere you are standing on, and whether it is hollow, or not.

 

Consider two hollow spheres. They both have the same mass, say 90 kg but one is half the radius of the other, say 1m and 2m. Your 1kg mass is at the same distance from the center of both, say 2m. I think you just need to show that the gravitation force from the sum of any pair of latitudes, North and South, will be the same for both spheres, and any hollow sphere of any radius, as long the radius is less than or equal to the distance to your 1kg mass. Take the 30th latitude +- 0.5 degress. They have the same mass, regardless of the radius of the sphere. In this case 1 kg, 0.5 kg per hemisphere, same as any other latitude, as long as the sphere is hollow. If the sum of the vertical component of the distances to the north and south latitudes are the same regardless of radius of hollow sphere, that should be sufficient, and that is of course the case. Whether you have a single hollow sphere, of a series of concentric hollow spheres to make up a solid sphere, it does not matter.

 

Yes?

[JustStuit]

Hmm. I'm not sure if I'm right, but particles that are not between the object and the center of gravity/mass of the earth will have less effect on the object. This is because they pull at an angle, and only part of it is toward the center of gravity. Therefore a hollow earth would have many more particles pulling at an angle because the only particles pulling directly downward are the particles right under the feet of the object and the particles exactly 180 degrees around the earth. The other particles, expecially those close to 90 degrees away, can pull at up to a 45 degree angle away from downward. Granted the effect would be small, but less particles are pulling down.

 

After thinking about that for a while, I am beginning to doubt myself. I forgot about the distance squared being divided in the gravity equation. In the hollow earth, the mass is closer to surface than an evenly dispersed or all in one point at center. I'm not really sure anymore.

[Prime-Evil]

Hmm. I'm not sure if I'm right' date=' but particles that are not between the object and the center of gravity/mass of the earth will have less effect on the object. This is because they pull at an angle, and only part of it is toward the center of gravity. Therefore a hollow earth would have many more particles pulling at an angle because the only particles pulling directly downward are the particles right under the feet of the object and the particles exactly 180 degrees around the earth. The other particles, expecially those close to 90 degrees away, can pull at up to a 45 degree angle away from downward. Granted the effect would be small, but less particles are pulling down.

 

After thinking about that for a while, I am beginning to doubt myself. I forgot about the distance squared being divided in the gravity equation. In the hollow earth, the mass is closer to surface than an evenly dispersed or all in one point at center. I'm not really sure anymore.[/quote']Its a neat problem isn't it. I'm 43 and I'm just getting it, I think, maybe.

 

Anyhow, it has to be a sphere, and you only need to be concerned with the vertical component, but it helps to break it down into concentric hollow spheres. You could use calculus, but you don't need to. Keep at it.

[frostbite]

will riddles count? the ones where in you will apply the basic concepts from physics down to mathematics, biology etc.

 

i'll try to browse my textbooks.. hehe!!