Laws of Motion/Rest?

K

Kumar

Registered Senior Member
Newton's First Law of Motion:
I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

This we recognize as essentially Galileo's concept of inertia, and this is often termed simply the "Law of Inertia".

The law of inertia states that:
A body will preserve its velocity and direction so long as no force in its motion's direction acts on it.

Newton's Third Law of Motion:
III. For every action there is an equal and opposite reaction.

Hello,

Motion and rest are two prime considerations in any science/system. Every/most of the aspects may be dependent on these two concepts.

Can you tell me:-

Differance in forces required for bringing same object into motion and into rest?

Alike laws of motion, are/can there some law of rest?

Best wishes.
 
Newon does have a law of rest - his first. A body at rest tends to stay at rest...

Rest is the absence of motion. There is a whole body of physics called "statics" that deals with forces applied-to/felt-by things at rest. A prime example of where this is used is structural members like roof trusses.

Under ideal conditions (i.e. absence of friction or losses - so perhaps floating in a vacuum) force required to say, accelerate a body to a certain speed would be the same scalar quantity (but applied in the opposite in direction) as the force required to bring it back to rest.
 
I think the important point here is inertia... I.e.. why is that to accelorate an object threw space requires the input of energy....
I.e.. if we apply energy to slow an object for example...
where did the energy go?

Can energy then be destroyed? and if so.. what does it become?

all of which suggests a missing component, which i would propose is the mystery of the physical relationship had between what we call matter and space.

i must ponder this.. likely for some time.
-MT (thankyou for mentioning it.)
 
Let me add:-

Motion
the act or an instance of changing position: an impulse or inclination of the mind or will

Motion
In physics, means a change in the position of a body with respect to time, as measured by a particular observer in a particular frame of reference.

Rest
1 freedom from activity or labor
2 a natural periodic loss of consciousness during which the body restores itself <after a long day, I lay down on the couch for a little rest before dinner>
Near Antonyms: pressure, strain, stress, tension
Antonyms: exertion, labor, toil, work

Rest(object)
A rest is an object used for supporting another, specific object, which is set to rest upon it (i.e. finding stability) and often diverts its weight to or by it.

Rest(physics)
Rest in physics and in the technical sense of geometric mensuration denotes a particular relation between a pair of observers.

Static exerting force by reason of weight alone without motion
: of or relating to bodies at rest or forces in equilibrium
: showing little change

Stable: marked by the ability to withstand stress without structural damage or distortion

Still: devoid of or abstaining from motion : free from storms or physical disturbance.

Stationary : fixed in a place or position: not undergoing a change in condition

Which of above is an true Antonyms of motion?

Whether an object require force/energy to remain in rest(or in antonyms of motion)?

Whether an object at rest tends to move toward motion in view of "Rest being a natural periodic loss of consciousness during which the body restores itself"?

Whether concept "rest" or any other antonyms of motion really exist on earth in view of earth remains in motion continiously and everything and being is also moving along with it? :p
 
Last edited:
Mosheh Thezion said:
I.e.. if we apply energy to slow an object for example...
where did the energy go?
Click to expand...
You have it a little backwards. If you slow an object down you get energy out of it. In other words, the object does work on whatever is slowing it. When you "apply energy" to an object you will always either increase its potential energy or speed. In that case the energy winds up as kinetic energy in the object itself.

-Dale
 
When an object in motion it/tool for its motion tends to loose energy and when at rest it may tend to gain/restore energy. (Rest: 2 a natural periodic loss of consciousness during which the body restores itself).

It may justfy third law of motion but how it can justify first law of motion or law of inertia?
 
Kumar said:
Whether an object require force/energy to remain in rest(or in antonyms of motion)?
Click to expand...
You are correct that it often requires force for an object to remain at rest, but not energy. Energy is the capacity to do work which in turn is a force applied over a distance. So if an object is at rest then the distance is zero so the energy is also zero, regardless of the forces involved.

This concept is particularly misunderstood for magnets. No more energy is being expended to keep a magnet at rest on your refridgerator than is expended to keep your monitor at rest on your desk.

Kumar said:
Whether concept "rest" or any other antonyms of motion really exist on earth in view of earth remains in motion continiously and everything and being is also moving along with it? :p
Click to expand...
You can always define a given object to be at rest by judicious choice of the coordinate system. However, if you choose a non-inertial coordinate system, then you will have to include some ficticious forces (http://en.wikipedia.org/wiki/Fictitious_force) in order to account for your accelerating coordinate system. The biggest of these ficticions forces in an earth-based coordinate system would be the Coriolis force (http://en.wikipedia.org/wiki/Coriolis_force). As long as the magnitude of this force is sufficiently small then you can treat your coordinate system as approximately inertial. This is a good approximation in most "everyday life" physics problems, but a bad approximation in meterology.

You are correct in noting that there is no truly inertial reference frame with objects on the earth being at rest. That is not really surprising considering that objects on earth are constantly experiencing forces. The forces are always slightly unbalanced leading to some acceleration relative to any inertial frame according to Newton's laws.

-Dale
 
Last edited:
Kumar said:
When an object in motion it/tool for its motion tends to loose energy and when at rest it may tend to gain/restore energy. (Rest: 2 a natural periodic loss of consciousness during which the body restores itself).

It may justfy third law of motion but how it can justify first law of motion or law of inertia?
Click to expand...
First, don't use that definition for rest in a physics problem since it is pretty useless to speak of objects having consciousness.

Second, I don't think you understand the history here. In classical physics Newton's laws are the first principles. The concept of energy was derived from Newton's laws, so you cannot use energy concepts to justify Newton's laws since it would be circular logic. As far as I know Newton's laws are not justified in any theoretical sense, they are only justified empirically. In other words, they fit the facts so well (in non-relativistic limits) that there is little reason to doubt them.

-Dale
 
Every motion, every movement in the universe is a means towards peace, towards equilibrium, absence of motion. Evolution is to become oneself. If I were already myself, I would not evolve, I would be at peace. But it's because I refuse myself, my nothingness, that I feel myself 'being' and subsequently am bound to become what I am.
 
DaleSpam said:
You are correct that it often requires force for an object to remain at rest, but not energy. Energy is the capacity to do work which in turn is a force applied over a distance. So if an object is at rest then the distance is zero so the energy is also zero, regardless of the forces involved.This concept is particularly misunderstood for magnets. No more energy is being expended to keep a magnet at rest on your refridgerator than is expended to keep your monitor at rest on your desk.
Click to expand...

We/object travel a distance with earth's movement even at rest.:) Thanks.



You can always define a given object to be at rest by judicious choice of the coordinate system. However, if you choose a non-inertial coordinate system, then you will have to include some ficticious forces (http://en.wikipedia.org/wiki/Fictitious_force) in order to account for your accelerating coordinate system. The biggest of these ficticions forces in an earth-based coordinate system would be the Coriolis force (http://en.wikipedia.org/wiki/Coriolis_force). As long as the magnitude of this force is sufficiently small then you can treat your coordinate system as approximately inertial. This is a good approximation in most "everyday life" physics problems, but a bad approximation in meterology.

You are correct in noting that there is no truly inertial reference frame with objects on the earth being at rest. That is not really surprising considering that objects on earth are constantly experiencing forces. The forces are always slightly unbalanced leading to some acceleration relative to any inertial frame according to Newton's laws.

-Dale
Click to expand...

Sorry, I am bit non-technical. How newton's first and third law of motion apply to an object in motion and at rest(still at motion?)?
 
Last edited:
c7ityi_ said:
Every motion, every movement in the universe is a means towards peace, towards equilibrium, absence of motion. Evolution is to become oneself. If I were already myself, I would not evolve, I would be at peace. But it's because I refuse myself, my nothingness, that I feel myself 'being' and subsequently am bound to become what I am.
Click to expand...

It is spritual or science's thought? Although may be logical fact, a definition of "salvation" or a definition of nature's balance/homeostatis, but I don't know how it can e possible? It somewhat tells, if prime force of all forces is there, it may be a peace/rest or balance uneffected by any motion.:) OK? :eek:
 
Kumar said:
Sorry, I am bit non-technical. How newton's first and third law of motion apply to an object in motion and at rest(still at motion?)?
Click to expand...
I am not sure that I understand your question. I think you are asking about how you can apply Newton's laws in a non-inertial reference frame. If so, please check out the links I provided earlier (http://en.wikipedia.org/wiki/Fictitious_force and http://en.wikipedia.org/wiki/Coriolis_force).

Basically, Newton's laws work just like normal except that you must include a fictitious force. This fictitious force does not really exist (that is why it is called fictitious), but it is necessary in order to explain the motion of objects in the non-inertial coordinate system. I believe that ficticious forces can be distinguished from real forces by Newton's 3rd law, i.e. there is no "equal and opposite" reaction force to a ficticious force, instead it is purely an artifact of the coordinate system.

If I missed the point of your question please try to rephrase it in more detail.

-Dale
 
Kumar said:
It is spritual or science's thought? Although may be logical fact, a definition of "salvation" or a definition of nature's balance/homeostatis, but I don't know how it can e possible? It somewhat tells, if prime force of all forces is there, it may be a peace/rest or balance uneffected by any motion.:) OK? :eek:
Click to expand...
It is not a scientific thought at all. It is pretty weak as far as spiritual thoughts go, IMO.

-Dale
 
Basically, Newton's laws work just like normal except that you must include a fictitious force. This fictitious force does not really exist (that is why it is called fictitious), but it is necessary in order to explain the motion of objects in the non-inertial coordinate system. I believe that ficticious forces can be distinguished from real forces by Newton's 3rd law, i.e. there is no "equal and opposite" reaction force to a ficticious force, instead it is purely an artifact of the coordinate system.

-Dale[/QUOTE]

How fictitious force does not really exists? Are these not considered as fictitious for the sake of understanding apparent motion by keeping earth's motion's effects as standard?

Anyway, When two exactly similar objects move in opposite directions with same force/energy--one in line of earths revolution and other opposite to it. What can be the difference in their motion?

Can different times and other plannet's influences at different times, effect the movements or rest (vibrations) of an object? For deeper thought--can this effect vibrations in atomic and molecular structures of an object?
 
Basically, Newton's laws work just like normal except that you must include a fictitious force. This fictitious force does not really exist (that is why it is called fictitious), but it is necessary in order to explain the motion of objects in the non-inertial coordinate system. I believe that ficticious forces can be distinguished from real forces by Newton's 3rd law, i.e. there is no "equal and opposite" reaction force to a ficticious force, instead it is purely an artifact of the coordinate system.

-Dale
Click to expand...

How fictitious force does not really exists? Are these not considered as fictitious for the sake of understanding apparent motion by keeping earth's motion's effects as standard?

Anyway, When two exactly similar objects move in opposite directions with same force/energy--one in line of earths revolution and other opposite to it. What can be the difference in their motion?

When two similar objects are at rest at two different places on earth, can there be some difference in naturally applied forces on them and in vibrations within them?

Can two adjunt objects at rest interfere/effect each other at naturally applied forces and so vibrations in them?

Can different times and other plannet's influences at different times, effect the movements or rest (vibrations) of an object? For deeper thought--can this effect vibrations in atomic and molecular structures of an object?
 
Last edited:
It looks that every object can't be at complete/true rest/peace at any time on earth (may be within solar system) due to plannetary movements...and always experiance some vibrations (vibrations in atoms and molecules).

Do plannetary movements cause and maintain these movements/vibrations and influence of gravity and sun resist these movements/vibrations?
 
>> can there some law of rest?

The Inertial State as per Newton's laws is confusing....
because no body in the Universe can be static (without motion), and all motion is in a curve (a straight line path can not exist )

so that law coined way back then has to be modified

So what is an inertial state ?

The only inertial state I have identified is exhibited by a cosmic body in circular orbit around a centre of spin....

Venus is very close to an inertial state..... this planet can be considered as "at rest" or inertial......it exhibits perpetual motion where all forces are in equilibrium...
 
Just to really confuse the issues RE: Laws of Rest

An inertial body is alway being accelerated...... it is under constant acceleration as it orbits the centre of spin.

so a good definition of inertia is

Matter that has constant velocity under constant acceleration is inertial.

This negates Einstein's claim that a body falling with gravity is 'inertial'.
 
URI said:
>> can there some law of rest?

The Inertial State as per Newton's laws is confusing....
because no body in the Universe can be static (without motion), and all motion is in a curve (a straight line path can not exist )

so that law coined way back then has to be modified

So what is an inertial state ?

The only inertial state I have identified is exhibited by a cosmic body in circular orbit around a centre of spin....

Venus is very close to an inertial state..... this planet can be considered as "at rest" or inertial......it exhibits perpetual motion where all forces are in equilibrium...
Click to expand...

Good thought.

unquote:
{Spritually venus is related to Goddess and goddess to force/energy.:}

What about Sun?

Can Sun and gravity can be considered as "rest causing entities".

Motion and rest are two prime aspects--may be a cause of everything. Earth's and plannetry's movements as cause of motion and gravity and sun as a cause to rest. Is it ok?

Whether an object tends to change its position in view of above influences...towards rest when in motion AND towards motion when at rest? Contractions & relaxations, hot & cold, day & night, dry and moist...may be relevant to motion and rest.(pendulum?)

The only inertial state I have identified is exhibited by a cosmic body in circular orbit around a centre of spin....
Click to expand...

Can it be axis?
 
You must log in or register to reply here.
Back
Top