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what does 'massive' mean in physics terms?

hi was readin my AS physics txtbook and saw that the proton and neutron are described as massive, does that just mean dense?
thanks guys

Reply 1

F1 fanatic

16

bobson

hi was readin my AS physics txtbook and saw that the proton and neutron are described as massive, does that just mean dense?
thanks guys

It means that they possess mass, ie they are not massless.

Reply 2

Theorist

10

F1 fanatic

It means that they possess mass, ie they are not massless.

I thought massive means something which possesses a lot of mass. No?

I guess it would make sense in the context bobson is talking about. Compared to electrons, nucleons are massive.

Reply 3

Wangers

16

F1 fanatic

It means that they possess mass, ie they are not massless.

Perphaps it is easier to define it as something which is indued with a discrete quantity of a property which allows them to be affected by gravity?

Reply 4

Nat89

1

Doesn't it mean that its something that has a large mass in a small area, so yeh it can be linked to density as the OP asked?

Reply 5

F1 fanatic

16

Nope, as far as I am aware, it has little or nothing to do with density, or with any context that implies "big" in our common usage of massive, it simply means that the particle is possessing of a property called mass. This could be seen as a property of gravity but I would avoid this. Photons are massless yet feel the effects of gravity (or rather the curvature of spacetime).

Basically "massive" = they have mass.

Reply 6

jobo3

1

F1 fanatic

Photons are massless yet feel the effects of gravity (or rather the curvature of spacetime).
.

They must have some mass I'd have thought. I know I don't know that much really, but E=mc^2, photons have energy, so they have mass. Also you can work out the momentum of a photon, mv = E/c.

I'm sure you know more about it than I do though.

:yy:

Reply 7

F1 fanatic

16

jobo3

They must have some mass I'd have thought. I know I don't know that much really, but E=mc^2, photons have energy, so they have mass. Also you can work out the momentum of a photon, mv = E/c.

I'm sure you know more about it than I do though.

:yy:

E=mc^2 only applies to the rest mass, ie you're in the rest frame. The full equation is:

E^2-p^2c^2=m^2c^4

Where for a particle at rest (or in the rest frame), p=0 and the second term vanishes. However, it is this term that provides the photon with it's energy, since it has no rest frame. It travels at the speed of light, and no massive particle may ever attain the speed of light. The fact it then feels the effects of gravity is a general relativistic effect.

Edit: From that same equation, you get that E=pc, which defines the momentum, rather than the equation you gave.

Reply 8

NesQuiK.

OP

13

ok, so basically, protons and neutrons are massive, cos' they have mass, which is much bigger relative 2 the electrons?

Reply 9

CommunistHamster

They have a non-negligible amount of mass.

Reply 10

F1 fanatic

16

bobson

ok, so basically, protons and neutrons are massive, cos' they have mass, which is much bigger relative 2 the electrons?

the relative size doesn't matter... an electron is massive also, anything that has non-zero mass is said to be "massive". The word has nothing to do with the word "big" we commonly associate with massive, like I said earlier.

Reply 11

ashy

17

Anything with mass is called massive. An electron is a massive object, as is Jupiter. F1F should know. As should I :p:

Reply 12

generalebriety

16

F1 fanatic

the relative size doesn't matter... an electron is massive also, anything that has non-zero mass is said to be "massive". The word has nothing to do with the word "big" we commonly associate with massive, like I said earlier.

Correct, but I suspect (for the OP's purposes) that electrons are being described as significantly "less massive" (excuse abuse of terminology) than protons and neutrons, i.e. that the mass of electrons can be disregarded. I know you're talking strictly dictionary definition here, but I'm sure that's what the intention of the author of this textbook was.

Reply 13

ashy

17

The quote doesn't really give enough information. There's no "massive, compared to so and so". Maybe he's just making the point that they have a mass? (although it might not be the best way to do it in an AS textbook)

Reply 14

F1 fanatic

16

I would personally read it that it's just being precise, what I quoted was something like the definition my A-level teacher gave back in the day. The point is a neutron and neutron do have mass, I don't get the impression this would be being referred to anything else.

Reply 15

Totally Tom

18

Which son of a b**** decided to confuse me by making me think massive meant big?

Reply 16

ashy

17

hamtomilton

Which son of a b**** decided to confuse me by making me think massive meant big?

Society in general?

Reply 17

MeAndBubbles

12

Could be a rudimentary classication of subatomic particles, althought not one I'm used to.

They're massive because they are subject to the strong force in the nucleus.

To conclude, electrons are considered point particles ie. pos. infinitely small point, and since they have mass, they must be infinitely dense if so.

Protons/Neutrons are not point particles, but contain quarks, and I can only think this is why massive is used, since electrons are also massive containing mass, but yeh significantly often described as 'negligble mass'. No wonder A'level students get confused.

Reply 18

teachercol

9

MassY might be a better term to use - but massive has stuck now.

Reply 19

Wangers

16

generalebriety

Correct, but I suspect (for the OP's purposes) that electrons are being described as significantly "less massive" (excuse abuse of terminology) than protons and neutrons, i.e. that the mass of electrons can be disregarded. I know you're talking strictly dictionary definition here, but I'm sure that's what the intention of the author of this textbook was.

Yes, generally in terms of A level anyway the mass of electrons is ignored since it is some 1/1600th of a proton, further since gravitational effects are negligible in the nucleus the effects of electrons are usually sadly relagated...

what does 'massive' mean in physics terms?

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