Matt Cooke of Minnesota Wild suspended 7 Games

Minnesnota · 1年前

I had thought, as a biproduct of the CBA, that your suspension history could only count against you for some small-ish amount of time (I can't remember how long, but I'm reasonably sure that Cooke has been clean for long enough).

Patol0tr · 1年前

No, this is just what determines what the acceleration is. When an object reaches terminal velocity (a constant velocity) the acceleration must be 0, so some other force must be acting on the body (wind resistance).

If we have no other force to act on the body (because we are in SPACE (!) ), then there is nothing to balance out the gravitational force, and the terminal velocity is....the speed of light (or, just a hair under..)!

Patol0tr · 1年前

So, if you're talking about 'acceleration towards the earth's surface' rather than just sense of acceleration due to force, the correct answer is they don't.

You're right! You've identified a good reason why Newton's laws don't really work in non-inertial (accelerating) frames of reference. The other massive body, still acclerates towards the earth the same as a very very light body (if we define our coordinate system in a "proper" inertial frame), but it is only because you've defined your frame of reference to be non-inertial that you see something "extra".

Patol0tr · 1年前

I'm not sure what you mean. An object's acceleration in a gravitational field is only related to the force it feels. It doesn't have anything to do with the relative sizes/masses of the objects.

edit: Ah, I think you are talking about relative acceleration as viewed from the earth. Nevermind!

jasoz377 · 1年前

What you're just described is actually called Compton scattering (and very visibly shows that photons carry momentum).

dp80 · 1年前

Yes, I see what you mean. And in some ways there are parallels between the ideas. However, just because the ether was wrong doesn't mean that the idea of a field permeating all space and time is a bad idea or wrong itself. We have lots of fields that exist on all space and time (electron, quark, photon, etc. fields have the same property...although the Higgs field is special in it's own unique way).

The idea that physicists propose something to make just to make the math work shouldn't make you too nervous though, it's how we do science. Propose solutions to problems, and try to either validate or exclude them. The ether was not a failure, but a success, of this method.

dp80 · 1年前

But now with the Higgs field, it sure looks like a repeat of the same thing; a hypothetical "field" that must exist in order to satisfy some equations

I think you actually have it a bit backwards here. The "ether" was proposed not to balance any equations, but was introduced in order to have match our physical intuition. Water waves need a medium to travel through (water), sound waves need a medium to travel through (air/gas/fluid), so what is the medium that light needs to travel through? The material that physicists came up with at the time was the ether...which was mostly a place holder for something that was not understood. It wasn't until later experimental observation noted that the ether couldn't exist. So no, it wasn't introduced to balance equations.

The Higgs field in a way was introduced to balance an equation (or rather to make local gauge invariance work for massive vector bosons, if you want to be technical). And, unlike the ether, we've observed it...or at least we've observed the excitations in the Higgs field, the Higgs boson.

I agree that sometimes it seems that the physicists "magic" something into existence in order to solve some math. And that's why we need experimental work, and it's why the ether has been discarded, but the Higgs field galvanized.

ABlackSwan · 1年前

are you saying that technically energy can be created, then, as long as the energy is then destroyed in a small enough time frame?

Yup :) As long as you still satisfy the uncertainty relation, then it works out.

ABlackSwan · 1年前

These are two very good questions.

Starting with the B- decay: The issue here is that the W- that decays is actually not a real particle, but a virtual particle. A virtual W- does not necessarily have the same mass as a real W- boson, and exists solely to transmit the weak force. Where does the energy come from? It comes from the uncertainty principle. Remember that \Delta(E)\Delta(t) >= h\bar/2. So if the W- boson exists for a small enough time, we can borrow some energy \Delta(E) and still satisfy the uncertainty relation.

For the B+ decay: I'll give you a hint first: We can't see this decay in sole protons (we've never observed proton decay). The only way the reaction is kinematically allowed is if the total energy of the final state nucleus is lower than the original. So, in fact, the energy comes from changing the binding energy of the nucleus.

Darrok · 1年前

Hi,

Sorry, I've pulled this thread. I was hoping we would get some good answers to start, but it's turning into a discussion, with little or no scientific evidence...which makes it better suited for /r/AskScienceDiscussion.

Would you mind posting it there?

lostgatherer · 1年前

I love the addition of the mini potion bottles. The entire costume looks great too. Kudos!

Elledan1211 · 1年前

So if Newton's third law were wrong, or absent from the universe

We always get into a little bit of trouble when we imagine stuff like this, which is far removed from what our universe looks like ;) The symmetry involved in applied forces is truly finely ingrained (and results from more fundamental symmetries, and things like momentum conservation...not easy things to chuck out the window!).

So, without newton's third law, you probably couldn't even push against the ball to begin with (if the billiard ball didn't push back on you, your hand would go right through it).

Sorry, I'm not giving you a straight answer!

cat_penis · 1年前

Examined by a person outside the car on the side of the road, the fly is travelling at 60+ mph. However, somebody inside the car would see the fly travelling at normal (not 60+ mph!) speeds. This is because the fly is travelling along the air inside the car, which itself is moving at 60 mph along with the car...so no super-human(/fly) feats are necessary.

Imagine a similar situation where you are on one of those moving sidewalks like you see at the airport. Let's beef it up, so once you stand on it, it starts moving at 60 MPH. Now you decide to start walking. You would be walking at 60+ mph, but of course that is only because the thing you are walking on is moving itself.

Elledan1211 · 1年前

I won't feel a 50 newton force being applied to me.

Sure you will :) But you are braced against the ground, pushing into the billiard ball, so perhaps you won't feel it the same way. Perhaps a better way to sniff out the return force is instead imagine slapping the ball. Notice how your hand hurts because of the force the ball exerted back on you?

Where is the energy for the reactiv 50 newton force coming from?

Now this is a tricky one. The energy comes from the electrostatic repulsion between the atomic electrons in your hand and the atomic electrons on the ball/earth/whatever.

Elledan1211 · 1年前

Is it because I'm not pushing myself up, I'm pushing the earth down?

I'd say that is the best way to look at it. You are pushing the earth down. Although, because of the third law, this is the same as pushing yourself up.

Perhaps most succinctly, the way to say it is: you are pushing the earth away from you (and it is doing the same to you).

Elledan1211 · 1年前

So going through your examples here a little piece by piece:

1) When you jump up, away from the earth, the earth does indeed also recoil against your push. The force you exert as you jump forces the earth to accelerate downward (by a very very small amount. The force you apply is small, and the mass of the earth is very very large). Meanwhile, due to the third law, the earth also imparts the same force to you. It is the same force, but it is acting on a very different mass (your mass). Since you have a small mass the acceleration will be larger, and you will travel a much larger distance than the recoiling earth does.

This also applies to the gravitational force that eventually stops you, and brings you back to the surface. The force being applied to you, and the earth are the same (the third law), but the masses these equal forces are being applied to are very different; this results in the acceleration on you being large, but the acceleration of the earth to be incredibly small.

2) With the balls hanging from ropes. Once again, we have the same issue. The forces applied are on the two balls are exactly the same. But remember, that the masses these forces are being applied to are different. Newton's third law does not say the accelerations are equal and opposite, it just says the forces are.

The large ball will swing down apply some force to the lighter ball as the lighter ball to the heavier. Since the lighter ball has lowish mass, it will have a higher acceleration, and will swing off wildly. Meanwhile, the same force applied to the very massive ball means that the acceleration will be very very small, and so the velocity will be changed by only a small amount, allowing the heavy ball to continue on without completely stopping.

To sum up: Forces are equal, but accelerations are not. The mass is the difference!

bestof2011 · 3年前

Can I also say that an awful lot of the crap/spammy/meme type comments we get are already down-voted to oblivion if they have been there for more than 20 minutes. So a big thanks to our readers...who are honey badgers in their own right!

KILLTHEREDDITOR · 3年前

http://www.reddit.com/r/askscience/comments/naxmk/the_everything_you_need_to_know_about_the_higgs/

I think this was was pretty good...although maybe a touch old?

ABlackSwan · 3年前

Hi!

this sounds like a homework question, and so is probably better suited for a post in /r/homeworkhelp. The post was automatically caught in the spam filter, but I think it would be better if you reposted it in a different sub.

thanks.

ABlackSwan · 3年前

Little pieces of everything pretty much. Indie, rock, hadrock, a bit of country and rap.

Been listening to a lot of Arcade Fire and Gorillaz lately.

ABlackSwan · 3年前

The mathematical physics courses I took in my undergrad were probably the toughest (but also the most fulfilling). The assignments were just ridiculous (30-40 pages, ugh).

but I learned soooo much from the course and that prof.

ABlackSwan · 3年前

pff...the safe answer

ABlackSwan · 3年前

Nitrogen...by a gorram landslide.

ABlackSwan · 3年前

TIL!

ABlackSwan · 3年前

I suppose the real way to say what I meant is that the bare mass term of all the fundamental particles that make up your body only constitutes 1-10% percent of your mass. Good catch :)

ABlackSwan

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