# Dambler force

1. Oct 4, 2005

### Alkhimey

Does Dambler (hope I spelled it right) fore is a real force or just something we use to explain things that we can't explain in other ways?

2. Oct 4, 2005

### pervect

Staff Emeritus
Could that be D'lambert force?

The rest of this response assumes that this is what you meant....

I'm never quite sure how to answer philsophical questions about whether or not something-or-other is "real".

Basic Newtonian physics will only work in inertial frames, a special sort of coordinate system. It can be generalized through Lagrangian mechanics to work in arbitrary coordinates.

Basically, I would say is that if one wants to learn about generalized forces, the safest thing to do is to go beyond Newtonian theory and study some Lagrangian mechanics, which is where the terms originated.

If one mixes and matches "generalized forces" aka D'Lambertian forces with Newtonian mechanics, one risks the possibility of making conceptual errors. Without knowing Lagrangian mechanics, it's safest to pick some inertial frame, write the equations of motion in that inertial frame, and then convert the variables to ones that one might actually be measuring. Sometimes shortcuts are taken, this isn't bad if they work correctly, it can be bad if one overgeneralizes the situations in which the shortcuts work correctly. When in doubt it would be best not to take the shortcuts and to explicitly pick an inertial frame and applying Newton's laws in that frame.

With Lagrangian mechanics, one does not actually have to worry overmuch about the "forces" at all. One can usually write down the Lagrangian of the system directly, and use Lagrange's equations to find the equations of motion - no more "free body" diagrams.

3. Oct 5, 2005

### Alkhimey

You misunderstood my question.
Does D'lambert force is a force tha excist in our everyday reality or it is something theoretical that excist only on the "papers"?
For example, the gravity force is real. I can sence it, I can feel it, I can see the affects of it.

4. Oct 5, 2005

### krab

Hmm. 3 spelling errors and 1 grammatical error (2 verbs; which one do you want us to use?). You might be asking an interesting question, but I don't know what it is.

5. Oct 5, 2005

### Alkhimey

Does D'lambert force excist in our everyday reality or it is something theoretical that excist only in the "papers"?

Hope all mistakes are correct now.

6. Oct 6, 2005

### Staff: Mentor

You chose a bad example. In general relativity, gravity is not a force. It's an effect of curved spacetime. Even from direct experience, gravity is different from other forces in that you can't actually "feel" it. Consider the astronauts in the space station or space shuttle. They're continually falling around the earth, subject only to the earth's gravity. Do they feel that "force"?

7. Oct 6, 2005

### Alkhimey

No they don't feel this force, but they feel the effects of it. After all, they don't fall out of the orbit. They can't feel gravity becouse the resultant force is 0.

8. Oct 6, 2005

### pervect

Staff Emeritus
If you were on a rotating space station, the "artificial gravity" would appear to your senses pretty much the same as "real gravity", therefore I would say that D'lambert forces are probably "just as real" as gravity according to your example of the defintion of "reality".

However, this is still a philosphical question, so it doesn't have any defninte answer, until you define what it means "to exist". While you haven't offered a defition, you have offered an example of something that you think is real, which allows me to take a shot at answering your quesiton.

Depending on the defintion used, note that it is perfectly possible for other people to assume that gravity is "not real", and to nonetheless calculate its effects very accurately.

9. Oct 7, 2005

### Alkhimey

Maybe you are right.
But we add D'lambert force to calculations that don't look logical to us. We even don't know why are we (I at least) doing it.
D'lambert force don't exist to someone that is standing out of the system, but when we stand inside the system the force appears real as gravity. (The artificial gravity you mentioned is one example for it)