# What is the difference of Dynamics and Physics?

1. Jan 26, 2010

### QasemAbughazl

I was discussing with a cohort the properties of force agianst certain materials. Like force upon wood, concrete, or brick for it to break or crack.

Is this Dynamics or Physics?

Other questions;

Does Dynamics fall under the general category-title-subject of Physics?

The study of blood flow, would this be dynamics or physics?

Q. A.

2. Jan 26, 2010

### Yehia11

Dynamics is a subcategory of physics.. it refers to motion and things that move.

the opposite is static.

:)

3. Jan 26, 2010

### zomgwtf

Dynamics is the study of forces acting on objects in regard to it's motion, making it move or changing it's motion.

I'm pretty sure that KINETICS is the study of moving objects and STATIC is the study of things that are still. These are further sub-categories of Dynamics.

4. Jan 26, 2010

### Klockan3

Physics is an extremely broad subject including many subtopics. Among them is mechanics. Mechanics have also several subtopics, one way to sort them is "statics" and "dynamics", usually statics is for static systems and dynamics is for systems with time dependence.

Physics do however include many other things. One example is electromagnetism, which in turn also have the subtopics statics and dynamics with the same meaning as above.

In high school you don't do this differentiation between the subjects. Instead they just say "Physics" and teach a bit of everything, among them a bit of mechanical statics and dynamics.
Nope, in most cases dynamics simply means all time dependant systems and do not include statics:
"Since the mid-20th century, the term "dynamics" (or "analytical dynamics") has largely superseded "kinetics" in physics text books[4]"
http://en.wikipedia.org/wiki/Kinetics_(physics [Broken])

Last edited by a moderator: May 4, 2017
5. Jan 26, 2010

### Astronuc

Staff Emeritus
One might be thinking of kinematics.

"Kinematics (from Greek , kinein, to move) is a branch of classical mechanics which describes the motion of objects without consideration of the causes leading to the motion. The other branch is dynamics, which studies the relationship between the motion of objects and its causes." en.wikipedia.org/wiki/Kinematics

kinematics—The branch of dynamics that describes the properties of pure motion without regard to force, momentum, or energy.
Translation, advection, vorticity, and deformation are examples of kinematic variables.
http://amsglossary.allenpress.com/glossary/browse?s=k&p=7

If takes into account viscosity or shear forces, then one is working in the realm of dynamics, or fluid dynamics/mechanics, or CFD.

6. Jan 26, 2010

### f95toli

A few years ago I published a paper with a title that started with "Dynamics of...". It wasn't until later I realized (when a colleague pointed it out to me) that this was actually a somewhat odd title since all we were doing was studying properties of a certain system as a function magnetic field, there was no time dependence.
For some reason we (and most other people in the field, which is presumably why neither the editors nor the referees noticed it either) referred to this as "dynamics", probably because there were some mathematical similarities to time-dependent systems if one replaced B with t.

7. Jan 26, 2010

### Basel A

dynamics is a branch of mechanics, which deals by the cause of motion. and as it is a branch of mechanicsm and since mecahnics is branch of physics then dynamic is branch of physics.

8. Jan 26, 2010

### Klockan3

Well, literary you weren't wrong, it is just that it have become a sort of convention to use "dynamic" as "time dynamic". As long as changing one quantity changes another you could call it dynamic and any subject dealing with that dynamics, but that is not the normal convention in physics.

9. Jan 26, 2010

### dacruick

I'm under the impression that what you are speaking of is materials. I believe that is the category. If you are ever checking the force on certain materials and measuring their properties that is more of an engineering application than anything

10. Jan 26, 2010

### zomgwtf

Well here is the definition from the dictionary:

dynamics [daɪˈnæmɪks]
n
1. (Physics / General Physics) (functioning as singular) the branch of mechanics concerned with the forces that change or produce the motions of bodies Compare statics, kinematics
2. (Physics / General Physics) (functioning as singular) the branch of mechanics that includes statics and kinetics See statics, kinetics
3. (Physics / General Physics) (functioning as singular) the branch of any science concerned with forces
4. those forces that produce change in any field or system

And that's how I learnt to define dynamics in physics.

11. Jan 26, 2010

### zomgwtf

You basically said exactly what I said... dynamics is the study of the FORCES involved... that's what I said. Kinematics is just the study of objects motion disregarding forces involved....

EDIT: I notice I said 'kinetics' is the study of... I meant to say that studying the forces causing objects to be in MOTION is called kinetics studying forces that cause objects to be still is STATICS both are fields of DYNAMICS... man that's confusing haha.

12. Jan 26, 2010

### QasemAbughazl

Wow , first off, thank all of you for your time and effort.

This discussion started last night while picking up my daughter from her dance lesson/studio, my sister asked if I could pick up my nephew from karate class (literally right up the street)

The Karate class were doing woodboard breaking.
I had turned to a parent there, whom I knew, and we got into a discussion.

I had said, that this part of martial arts is more about Physics.

I had replied; "Dynamics is a study within Physics falling under such category"

He went on to state that I was still "incorrect as Physics had to do with blood flow..."

But looking upon the material , per its pre-determined size, thickness, type - per selection , it would seem that breaking boards is far more involved that actual power or skill demonstrating. Besides physics-dynamics, it may also be issues of mentality per courage, focus, and confidence

It would seem less of power generated by the person and more of skill (to be trained to focus and use a proper technique of speed-velocity thereof applied)

Although, I have seen non martial artists at parties perform breaks (teenage- college goofing), there maybe no training involved. Simply, a party or parlor trick

Because I work for a engineering firm,
and I am not in school to ask a teacher-professor of physics/physicist,
I thought I'll ask someone here..

QA

13. Jan 27, 2010

### Klockan3

How old is that dictionary? And how would you fit a field like electrodynamics into that?

http://wordnetweb.princeton.edu/perl/webwn?s=dynamics
http://en.wikipedia.org/wiki/Dynamics_(physics [Broken])
http://www.yourdictionary.com/dynamics
http://www.britannica.com/EBchecked/topic/175182/dynamics

Then I also found this:
Note the date...
http://www.merriam-webster.com/dictionary/Dynamics
As a comparison look at what you get when you search for rocket, a set of plants and nothing else:
http://www.merriam-webster.com/dictionary/rocket

Last edited by a moderator: May 4, 2017
14. Jan 27, 2010

### Pythagorean

Sounds like biophysics to me! If the flow is steady, it may be considered dynamic, but I'm thinking it probably has a somewhat periodic function based on the heart.

By the way, did you know if we didn't have a buffer zone, our hearts would shake us about like a ragdoll?

15. Jan 27, 2010

### QasemAbughazl

So these Karate people breaking a stationary object is "Static"?

Whereas, if they threw it in the air and broke it-mid air while they or it moving is "Dynamic"?

16. Jan 27, 2010

### Pythagorean

I would call something breaking dynamic. Wood and brick, for instance, would break apart in a dynamic way.