Welcome to Junkyard Physics - Learn & Teach Here!

[MrREC]

That formula comes from special relativity, not general. Here's a more fundamental one: F = ma. It encodes the fact that the net force (F) on an object is proportional to the net acceleration (a) that the object experiences. The mass (m) of the object is the constant of proportionality. Again, forget the formula, what is the layman's explanation of this phenomenon?

If I hit a nail with a big enough hammer, and hard enough, then it will drive into a board ?

edit: with a loss of acceleration of the nail due to friction?

also: If the nail bends, or the board wood is too dense to insert the nail you physics types will form three commitees made up of many undergrads. One to create a formula to study the nail and find out why it bent. The second will do the same to find out why the board was so hard. The third will study the hammer and then all of you will get together and argue about how to fix it for a month.

In the junkyard we just go get a stronger nail and a bigger hammer. Works every time.

 

[HeLiXe]

Welcome MrREC It is great to want to learn physics and to be enthusiastic. When you begin to study physics with the equations, math and all, it is quite different from reading popular books and watching documentaries etc. I was attracted to physics when I encountered it in chemistry in high school, my high school did not offer it. The popular representation of physics is very romantic and eerie, but when you begin to study it, it can be very fundamental and exacting so this is why three scores of undergrads may study the nail and this is why many are asking specifically what you are meaning by appending the word "junkyard" to physics. When you begin to study more I think you will appreciate why others are saying you should not really teach until you have a better understanding...until then people may seem pompous. Don't get me wrong there are some people who are pompous, but they usually do not have extensive knowledge. Many of the people who responded here I have found are not the pompous type...but just be careful with your answers combined with wanting to teach because you may end up banned.

 

[Gordianus]

If I hit a nail with a big enough hammer, and hard enough, then it will drive into a board ?

edit: with a loss of acceleration of the nail due to friction?

also: If the nail bends, or the board wood is too dense to insert the nail you physics types will form three commitees made up of many undergrads. One to create a formula to study the nail and find out why it bent. The second will do the same to find out why the board was so hard. The third will study the hammer and then all of you will get together and argue about how to fix it for a month.

In the junkyard we just go get a stronger nail and a bigger hammer. Works every time.

Many years ago I visited Kennedy Space Center where I enjoyed a nice computer game: "Design your own rocket". I could choose the number of stages, engines, amount of fuel, etc...
Let's say my first ten "designs" (made by trial and error) were horrible. Whenever I tried a bigger something, things got worse. Finally I read a bit about rocket design and discovered not always a bigger "nail" solves a problem.

 

[Jimmy Snyder]

If the nail bends, or the board wood is too dense to insert the nail you physics types will form three commitees made up of many undergrads. One to create a formula to study the nail and find out why it bent. The second will do the same to find out why the board was so hard. The third will study the hammer and then all of you will get together and argue about how to fix it for a month.

This isn't about how you can explain physics at all is it? It's about how you know more physics than the physicists do.

 

[WannabeNewton]

I find this thread amusing. Physics is much more pleasing and much, much, much more elegant if you learn the associated mathematics. If you like physics so much I don't see why picking up a textbook of the appropriate caliber and working your way up is an impossible task. Hell of a lot more productive than endorsing "junkyard physics" that's for sure.

 

[bp_psy]

If I hit a nail with a big enough hammer, and hard enough, then it will drive into a board ?

edit: with a loss of acceleration of the nail due to friction?

also: If the nail bends, or the board wood is too dense to insert the nail you physics types will form three commitees made up of many undergrads. One to create a formula to study the nail and find out why it bent. The second will do the same to find out why the board was so hard. The third will study the hammer and then all of you will get together and argue about how to fix it for a month.

In the junkyard we just go get a stronger nail and a bigger hammer. Works every time.

Well those dumb physics undergrads will figure exactly how big that hammer and how strong that nail should be in order to not break the board or hurt themselves.

 

[edward]

If I hit a nail with a big enough hammer, and hard enough, then it will drive into a board ?

edit: with a loss of acceleration of the nail due to friction?

also: If the nail bends, or the board wood is too dense to insert the nail you physics types will form three commitees made up of many undergrads. One to create a formula to study the nail and find out why it bent. The second will do the same to find out why the board was so hard. The third will study the hammer and then all of you will get together and argue about how to fix it for a month.

In the junkyard we just go get a stronger nail and a bigger hammer. Works every time.

Forming committes seems to be a part of human nature. The comittees may possibly determine that the nail must be hit squarely and more than once.

You may enjoy this game based on physics.

http://fantasticcontraption.com/

And here is the newest version.

http://fantasticcontraption2.net/

 

[MrREC]

Thanks for the support from some of you.

I may be too old and intellectually incapable of learning calculations and formulas. (I failed 0800 algebra 1 and then failed part 2). That was 20 years ago.

As far as "value added" goes don't discount a lifetime of wisdom, knowledge, adventure and yes teaching.

I was once told that physics is the study of the universe big and small. No one person can understand it all though and added knowledge can come from some supprising places.

I was once at the funeral of a dear friend of my mothers. The deceased's brother in law was there. This brother in law is a top notch physicist. I spent an hour discussing some topics and books that I had read on physics related material. His later comment to my elderly mother was that he was suprised that I had read material that even he hadn't had a chance to get too.

I had an interesting conversation with a forensic scientist/ rocket scientist the other day at my phyciatrists office. Same feedback. The guy was impressed.

My point is still this...We are not all alike in our abilities. My use of the nail and the commitee analogy was saracasm and I do apologize.

"Value added", "Junkyard physics" it all comes down to give and take and a bunch of folks looking at the universe and wondering why....

 

[HeLiXe]

Yes I sort of felt you were coming from this angle. It is just that here (on this site) there are a lot of students and people learning physics, so when you say "teach" it is taken very seriously because a lot of care is taken to give quality info on this site...which is why I was saying to be careful. I was the same way for most of my life...looking at the universe and wondering why. I still am that way and am happy that I am finally getting a chance to study it.

Have you ever tried to learn algebra again?

 

[MrREC]

Yes I sort of felt you were coming from this angle. It is just that here (on this site) there are a lot of students and people learning physics, so when you say "teach" it is taken very seriously because a lot of care is taken to give quality info on this site...which is why I was saying to be careful. I was the same way for most of my life...looking at the universe and wondering why. I still am that way and am happy that I am finally getting a chance to study it.

Have you ever tried to learn algebra again?

No I've been pretty sick for the last 12 years. I'm generally not allowed to do things that get my blood pressure worked up. (like antagonizing folks that might "smoke" my computer :tongue: ).

If I use analogy to try and "teach" a point it might lead to a breakthrough in some. If I am wrong then there are plenty of "committee" members here to barbacue my butt.

However: Was I even close with the nail, hammer, and board answer to the formula question?

 

[Hurkyl]

However: Was I even close with the nail, hammer, and board answer to the formula question?

IMO, not really... your scenario is the sort of a thing I imagine presenting to a student and asking to analyze. There's actually a lot going on if you want to break it down into the individual parts, but the main feature of your example is simply gravitational potential energy -- a bigger hammer means more energy input from that source -- especially with a classic hammer stroke where the human just guides the hammer and let's gravity do the work.

In fact, it's quite difficult to talk about the force (in the sense of physics) with which the hammer strikes the nail, since it depends very, very much upon the duration of the impact of the hammer with the nail*. When a layperson would ask "what is the force (in the sense of English) with which the hammer strikes the nail?" they really mean something more like "momentum" or "energy" or "impulse" (those words meant in the sense of physics).

*: and possibly on material properties of hammerheads, nails, and boards, to control whether the force is essentially constant for the duration of the impact, or if it varies



(I'm 99% sure of the following physical claims)
If you were swinging the hammer horizontally (i.e. the hammer remains horizontally level for the entire stroke), you might be surprised to find that the size of the hammer doesn't actually have any direct effect on your ability to drive the nail. A bigger hammer can still help, but for the following reasons:

• The hammer accelerates more slowly, giving you a greater amount of time over which your muscles can supply energy
• The hammer moves more slowly for the same amount of energy, allowing you to swing it more safely

(that first point is actually a decent example of F=ma -- in particular the relationship of mass to acceleration when holding force constant)

 

[MrREC]

IMO, not really... your scenario is the sort of a thing I imagine presenting to a student and asking to analyze. There's actually a lot going on if you want to break it down into the individual parts, but the main feature of your example is simply gravitational potential energy -- a bigger hammer means more energy input from that source -- especially with a classic hammer stroke where the human just guides the hammer and let's gravity do the work.

In fact, it's quite difficult to talk about the force (in the sense of physics) with which the hammer strikes the nail, since it depends very, very much upon the duration of the impact of the hammer with the nail*. When a layperson would ask "what is the force (in the sense of English) with which the hammer strikes the nail?" they really mean something more like "momentum" or "energy" or "impulse" (those words meant in the sense of physics).

*: and possibly on material properties of hammerheads, nails, and boards, to control whether the force is essentially constant for the duration of the impact, or if it varies



(I'm 99% sure of the following physical claims)
If you were swinging the hammer horizontally (i.e. the hammer remains horizontally level for the entire stroke), you might be surprised to find that the size of the hammer doesn't actually have any direct effect on your ability to drive the nail. A bigger hammer can still help, but for the following reasons:

• The hammer accelerates more slowly, giving you a greater amount of time over which your muscles can supply energy
• The hammer moves more slowly for the same amount of energy, allowing you to swing it more safely

(that first point is actually a decent example of F=ma -- in particular the relationship of mass to acceleration when holding force constant)

The equation F=ma did not allow for a variable in the duration of the force so I assumed that it was an instant transfer of kinetic energy from the hammer to the nail. The energy was then consumed in different ways. Acceleration of the nail, heat dissipation as the nail encountered friction from the board, and sound waves from the impact at the nail head as well as point of entry into the board. There may also have been some loss of energy due to flexing of the nail as well.

By using a bigger hammer and stonger nail then I am changing two of the variables, but the formula remains the same. Bigger hammer equals more force (F). Stronger nail implies bigger or heavier density (M) thus acceleration (A) should increase ...right?

If I were to strike a nail (M) with a hammer(F) in a weighless vacuum (with no board) then acceleration (A) would remain constant in proportion to the force applied.

The same being true with a bigger hammer and heavier nail.

It seems as though my answer would have satisfied the equation in "laymens terms" even though I added no numbers to solve the equation. I only tried to explain how the formula worked without adding numbers to the equation. Of course the board was a variable [resistance (r?) ] that I added as a prop to the scenario (Sorry about that).

I might not have been right but I don't think I was wrong either.

Part of my main point ...nobody ever seems to agree on the right answer.

 

[Dadface]

It seems that MrRec is being tested here and perhaps unfairly.In this forum one is not thrown questions and asked to answer them but one has the opportunity to choose to respond to certain questions.That choice is governed by several factors such as what has already been discussed in the thread,the described or imagined level of expertise of the questioner and at what level to pitch the answer and,of course,the area of interest and expertise of the potential respondant.
I think most people here are selective and respond only to those questions which they find interesting and where they are reasonably confident that they have something helpful and constructive to contribute.

 

[MrREC]

It seems that MrRec is being tested here and perhaps unfairly.In this forum one is not thrown questions and asked to answer them but one has the opportunity to choose .....

Thank you for your response.

The main reason that I am being tested is that I had the "gall" to suggest that I could maybe "teach" someone something.

As I have stated I am NOT a physicist. I AM interested in physics though.

I have been a teacher in the past and I have found that there are other things needed to present a subject other than just the facts.

Humility, deference, humor, skeptisim, unorthodoxy, and other things can enliven a quest for knowledge.

Maybe the moderators should consider a "Junkyard physicists" forum for the oddballs, crackpots, and the intellectually challenged such as myself. It might keep us from wandering the sacred halls until we get a firmer grip on what we wish to ask or answer. I'm sure that guest mods would love to peek in every now and then to "whip" us into shape.

It seems like a good compromise. One that would allow us gnats a place, and with the added bonus of not having us clutter up the main forums, or potentialy get banned for being "out of line".

Any input on that suggestion folks.

edit: also...I am an English Lit major not linguistics, spelling, or grammar. I can read English quite well just not spell it, speak it, or write it, to the level of some peoples expectations. (Including mother)

 

[zoobyshoe]

An equation derived by the twentieth-century physicist Albert Einstein, in which E represents units of energy, m represents units of mass, and c2 is the speed of light squared, or multiplied by itself.

Read more: http://www.answers.com/topic/e-mc2#ixzz1WFn8RkvZ

Where am I not close?

I said basically the same thing other than using (C2) as the speed of light. Where was I wrong?

The next sentence of your link says:

Because the speed of light is a very large number and is multiplied by itself, this equation points out how a small amount of matter can release a huge amount of energy, as in a nuclear reaction.

So, the layman's explanation is that E=mc² tells us that a huge amount of energy is locked up in even a small amount of matter. A nuclear explosion is one example of what happens when even a small portion of that energy is suddenly released (atom bomb = something like 7% of the available energy).

You didn't basically say the same thing. You were way wrong, barking up a completely different species of tree:

The formulation gives you the stucture to calculate how to move an object (m)mass to a certain velocity (C) using a quantity of energy(E).

How much nitro methane do I need to move a dragster down a quarter mile strip (at 300 mph) without having to carry any extra weight in fuel.

Similar is it not?

E=mc² doesn't tell you how to accelerate your dragster with a given amount of energy. It tells you that, if you could release the energy locked up in the mass represented by your dragster (since we're talking about dragsters) you could level a city, or, released more slowly and in a controlled way, supply that cities energy needs for a year (by which I mean, a surprisingly long time). The formula tells you that the mass of a dragster represents a certain number of joules of energy, and that amount is surprisingly tremendous. Unfortunately, it's "locked up" as I keep saying. There's no way to release and utilize it except in the case of radioactive elements, and that only gets you a small percentage of what's actually there.

The energy we're talking about isn't the chemical energy represented by fuel. It's about atomic forces. There are forces at work in atoms such that they're trying to fly apart, and counter forces that are keeping them together. The combined energy all those forces might produce is huge.

I don't think there's anything at all wrong with math-less layman's explanations as long as they're on target. I'm still baffled by the fact that you googled an answer that was basically right but then presented an answer that was wrong.

 

[TurtleMeister]

Thank you for your response.

The main reason that I am being tested is that I had the "gall" to suggest that I could maybe "teach" someone something.

Any member can answer questions and give advice. But if you're a layman, like myself, you will have to be careful. Don't just go on your intuition. That would not go over very well here. If you're not sure, then look it up and do some research beforehand. Or just don't answer at all.

Maybe the moderators should consider a "Junkyard physicists" forum for the oddballs, crackpots, and the intellectually challenged such as myself.

You are obvioulsy new here and have not lurked around. What you suggest will never happen at PF.

I notice that your thread was moved from "General Physics" to "General Discussion". In this sub forum the members tend to be "not so serious" and will sometimes joke around with each other. Such as my post #26. So your feeling of being flamed may be a little unwarranted.

 

[HeLiXe]

No I've been pretty sick for the last 12 years. I'm generally not allowed to do things that get my blood pressure worked up. (like antagonizing folks that might "smoke" my computer :tongue: ).

If I use analogy to try and "teach" a point it might lead to a breakthrough in some. If I am wrong then there are plenty of "committee" members here to barbacue my butt.

Well done?
You should try it again You might surprise yourself. Start from your level of math and work your way up :)

However: Was I even close with the nail, hammer, and board answer to the formula question?

Spot on! This is the sort of things physics undergrads would analyze the heck out of :tongue2:
Well when I saw it I thought the same as Hurkyl with this

IMO, not really... your scenario is the sort of a thing I imagine presenting to a student and asking to analyze.

You gave a scenario as opposed to an explanation...albeit a very good scenario with lots of forces at work. But I understand you were thinking of the mass of the hammer being accelerated and equaling a force (visible by the hammer hitting the nail). For the rest Hurkyl answered you better than I could. I am taking physics I next semester. I studied some basic kinematics before I withdrew this past term...but you probably know more about physics than I do

 

[MrREC]

Mmmmm Mmmmmm Boston butt well done.

So the energy used to cook my...errr the butt is not the same as the potential atomic energy of the atoms in the charcoal. Burning the charcoal only ionizes the electrons thus releasing very little energy as heat?
Whereas; splitting just one of the carbon atoms in the charcoal would barbecue every butt in town?

I guess my mistake was in not thinking of the ability to convert the dragster into energy?

I started to use the analogy of (E) being the energy = to (Mass) a spaceship*(c2). Where a spaceship used the energy of an atomic bomb to move it toward the speed of light. Then I remembered that no known spaceship could carry enough fissionable material to get any where near the speed of light. So I tried to "wing" it with the dragster analogy.

Ah well... smoked crow and butt.

Edit: just for clarity...what formula would you use to calculate how much nitro methane it would take to move a dragster 300mph down a 1/4 mile strip without having any extra fuel left over?

*engine displacement: 500 cubic inches: power: 8000 horsepower at 8200 rpm: weight: 2300lbs. wheelbase: 300 in. engine block: Brad Anderson Enterprises,

In a typical run the engine can consume as much as 103 litres (22.75 gallons) of fuel during warmup, burnout, staging, and the quarter-mile run. (Wiki)

There is a "scenario'. Can it be expressed in a simple formula?

 

[MrNerd]

With Einstein's e = mc^2, it simply shows that mass is a form of energy. The only way that I know of to actually get all that energy is pair annihilation, which is normal matter colliding with antimatter. However, it is exceedingly difficult and uneconomical to produce antimatter for anything other than research. However, the equation also works the other way. Accelerating an object increases its kinetic energy. Because it has more energy, it now has a very slightly higher amount of mass.

If you want an overview of random math, I found a book at my library that might help. It's called Mathematics 1001. Its only 400 or so pages, and it has a lot of information, even in the brief miniarticle format it uses, on stuff that isn't taught at high schools at all anywhere that I know of. Things like number theory, for example, would have entries in the book like egyptian fractions. There's also some physics math at the end, and recreational math like magic squares and other interesting things. Keep in mind, however, that I'm pretty sure it's not meant to be used as a complete textbook on the things. I think it's more like an overview to show you new things that other books don't even acknowledge as existing. There's some algebra in it, too, so it might be able to help you with that, since you posted earlier that you failed it.

 

[MrREC]

With Einstein's e = mc^2, it simply shows that mass is a form of energy. The only way that I know of to actually get all that energy is pair annihilation, which is normal matter colliding with antimatter. However, it is exceedingly difficult and uneconomical to produce antimatter for anything other than research. However, the equation also works the other way. Accelerating an object increases its kinetic energy. Because it has more energy, it now has a very slightly higher amount of mass.

If you want an overview of random math, I found a book at my library that might help. It's called Mathematics 1001. Its only 400 or so pages, and it has a lot of information, even in the brief miniarticle format it uses, on stuff that isn't taught at high schools at all anywhere that I know of. Things like number theory, for example, would have entries in the book like egyptian fractions. There's also some physics math at the end, and recreational math like magic squares and other interesting things. Keep in mind, however, that I'm pretty sure it's not meant to be used as a complete textbook on the things. I think it's more like an overview to show you new things that other books don't even acknowledge as existing. There's some algebra in it, too, so it might be able to help you with that, since you posted earlier that you failed it.

Thank you for your post.
I may look for some 0800 -1001 level math books when I go to the library next week.

If y'all can tolerate my ignorance then the least I can try to do is to work toward eliminating as much of it as I can.

That is the key to unlocking the gates of the "Junkyard".

Thanks again.

 

[zoobyshoe]

In a typical run the engine can consume as much as 103 litres (22.75 gallons) of fuel during warmup, burnout, staging, and the quarter-mile run. (Wiki)

There is a "scenario'. Can it be expressed in a simple formula?

w+b+s+r is less than or equal to 103 litres

where:

w=warmup

b=burnout

s=staging

r=quarter mile run


(I don't know how to create the "is less than or equal to" sign here.)

 

[MrREC]

w+b+s+r is less than or equal to 103 litres

where:

w=warmup

b=burnout

s=staging

r=quarter mile run


(I don't know how to create the "is less than or equal to" sign here.)

Interesting... but how about w(t)+b(t)+s(t)+r(t) < > or = 103 litres

with (t) being a time variable?

 

[HeLiXe]

w+b+s+r is less than or equal to 103 litres

where:

w=warmup

b=burnout

s=staging

r=quarter mile run


(I don't know how to create the "is less than or equal to" sign here.)

ahhhh at last an equation for academic burnout

 

[MrREC]

ahhhh at last an equation for academic burnout

Or "rope" burnout. I could always do the warmup, staging, and get to the burnout part, but the 1/4 mile run always took a backseat to the munchie run.

 

[DoggerDan]

Junkyard physics is fine with me. I understand basic physics well enough, but when you start using all the math, I'm lost.

 

[MrREC]

Junkyard physics is fine with me. I understand basic physics well enough, but when you start using all the math, I'm lost.

Pretty much most of my point. I'm sure you can add something to the forums as well.

Welcome.

 

[khemist]

The mathematics is not here to confuse you. If one wants to truly understand the forces at work (no pun intended :P), one must understand the mathematics behind it.

For example, in quantum mechanics there are quite a few things that happen that cannot be described by simply using english, and to be precise one must employ math to become specific. However, this math is still abstract, and we are not able to answer the question of why, but rather be able to make very accurate predictions given a particular situation.

 

[MrREC]

The mathematics is not here to confuse you. If one wants to truly understand the forces at work (no pun intended :P), one must understand the mathematics behind it.

For example, in quantum mechanics there are quite a few things that happen that cannot be described by simply using english, and to be precise one must employ math to become specific. However, this math is still abstract, and we are not able to answer the question of why, but rather be able to make very accurate predictions given a particular situation.

Another equally valid point. I am not trying to discredit the hard work and dedication of those that can understand the math. I'm just trying to see if there is some "middle ground" where "some" people can "translate" complex ideas into "plain English".

If it can't be done then it can't be done. I'm sure that those of us that cannot "do the math" are not going to complain (much), but instead will be delighted when someone can "translate" complex ideas into a more understandable form.

It seems that we all wish to learn to some degree.

 

[Evo]

Sorry, this thread was supposed to be closed 3 pages ago. The answer is no. If a member doesn't understand an answer, they can ask a mentor or science advisor to explain it in simpler terms, but honestly there is a limit to how simple you can get and still be carrying the correct meaning. Someone would need to have a high level of understanding in order to do this correctly.