Ask a physicist anything. (2)

[canehdianhotstuff]

F= -kx ?

 

[pgp_protector]

E=MC[sup]2[/sup]

 

[canehdianhotstuff]

So it is what I said. The mass of an object is equal? to it;s energy and thus closing the box adds more energy making the box heavier...just slightly.

 

[Wiccan_Child]

E=MC[sup]2[/sup]

Surely you don't mean that closing the lid adds energy, and thus mass, to the box? Because I have legal documentation confirming that this is not a valid answer:

You're in a sealed room, their is a scale on the table & a open Jack-In-The-Box.
You have to make the Jack-In-The-Box weigh more.
How can you do this without adding anything to the Jack-In-The-Box?

 

[catzrfluffy]

Because winding it adds energy, increasing the mass?

 

[pgp_protector]

Surely you don't mean that closing the lid adds energy, and thus mass, to the box? Because I have legal documentation confirming that this is not a valid answer:

I need to listen to the book again to get the question fully correct

 

[pgp_protector]

Because winding it adds energy, increasing the mass?

Yep.

(Or you could heat it also)

 

[Cabal]

I don't like this riddle.

 

[canehdianhotstuff]

Im just going to put a finger print on it and make it weigh 0.000001gram more.

 

[sbvera13]

I would have taken the Jack off the table and put it on the ground. Being infinitesimally closer to the Earth's center of mass should make it weigh infinitesimally more.

The question didn't say you had to increase it's mass Just it's weight.

 

[sbvera13]

Im just going to put a finger print on it and make it weigh 0.000001gram more.

That would be adding something to it.

 

[Cabal]

I would have taken the Jack off the table and put it on the ground. Being infinitesimally closer to the Earth's center of mass should make it weigh infinitesimally more.

The question didn't say you had to increase it's mass Just it's weight.

This one, I like.

 

[pgp_protector]

I would have taken the Jack off the table and put it on the ground. Being infinitesimally closer to the Earth's center of mass should make it weigh infinitesimally more.

The question didn't say you had to increase it's mass Just it's weight.

Good one

 

[Supreme]

Physics is my weakest science, and I no longer study it. Could you explain circular motion to me?

So far I've grasped:

Objects that go around in a circle have a force called centripetal force.
Centripetal force is not a force in its own right and depends of other forces (eg gravity)
The object is always accelerating because it is always changing velocity (this bit I've never really understood).

Cheers.

 

[Wiccan_Child]

Physics is my weakest science, and I no longer study it. Could you explain circular motion to me?

So far I've grasped:

Objects that go around in a circle have a force called centripetal force.
Centripetal force is not a force in its own right and depends of other forces (eg gravity)
The object is always accelerating because it is always changing velocity (this bit I've never really understood).

Cheers.

To understand why the object is always accelerating, it's best to think of a small object orbiting a large object (e.g., a satellite and the Earth). As the satellite moves forward, it's constantly being pulled by the Earth's gravity: in other words, it's constantly under acceleration. However, the satellite is also moving 'forward' (that is, at a 90° angle to the direction gravity is pulling in). So gravity is pulling it down, and its own velocity is moving it forward. The net result is that it moves forward and down at the same time.

Now, if you get this just right, the object won't have changed its distance from the Earth: though it would have moved forward, and thus moved farther from the Earth, gravity will have pulling it inwards, keeping it at the same distance. In other words, it's moving in a circle.

Or you can think of it this way: the object tries to fly off in a straight line, while the Earth pulls it round due to gravity. Because the 'straight line' it's trying to fly off in has now changed due to gravity, we say that it has accelerated: acceleration is any change in velocity, and velocity is 'speed with direction'. So velocity can change, even if your speed does not.

Confusing, isn't it?

Basically, gravity cures an objects trajectory round. If the velocity is just right, the path it will take will actually curve round onto itself, and it will thus be orbiting the Earth. This image shows what happens to the path of the object if it has different velocities; in some cases it flies off, in others it curves round.

Second, the object is always accelerating because it's always falling to Earth: gravity is always pulling it downwards, its velocity is always changing.

 

[AV1611VET]

I dub this drawing: HAECKEL'S TRAJECTORIES.

(Just kidding --- )

 

[TerranceL]

Something occurred to me the other day.

I'm sitting in my room. Sitting still.

But my house is sitting on a tectonic plate that is moving.

That is sitting on a planet that is spinning.

That planet is orbiting a star.

That is orbiting the black hole at the center of the galaxy.

That is moving with another cluster of galaxies.


Question:

Did I leave anything out?

Anybody have ANY idea how fast i'm actually moving?

Is there anything in the universe that doesn't move?

 

[Tinker Grey]

Anybody have ANY idea how fast i'm actually moving?

Is there anything in the universe that doesn't move?

With respect to ... ?

I don't know the answer to your question, but I think (and I think your second question implies that you do to) that one needs a reference point.

It may be that any given thing is moving with respect to any other given thing in the universe.

I suspect, too, that my if my speed WRT to some object X is V, that implies that X's speed with respect to me is also V. The question is then, what is moving and how does one tell.

The question is also complex because for any given reference point there is going to be different components. For example, the earth's rotational speed averages to zero (that is, it doesn't contribute) to your average speed rotating about the center of our galaxy.

But, I await the experts ...

 

[catzrfluffy]

What is between atoms?

 

[Tinker Grey]

A deep affection?