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Jumat, 26 Oktober 2012

physics: Newton's law

isaac newton said thatNewton's laws of motion are three physical laws that form the basis of classical mechanics. This law describes the relationship between the forces acting on an object and the motion they produce. This law has been written with a different pembahasaan for nearly three centuries, and can be summarized as follows:

    
First Law: Every object will have a constant velocity unless a non-zero resultant force acting on the object. Meaning if the resultant force is zero, then the center of mass of an object remains at rest or moving at a constant speed (not accelerating).
    
Second Law: A body of mass M having the resultant force of F will accelerate a direction similar to the direction of the force, and the magnitude is

proportional to F and inversely proportional to M. or F = Ma. It could also mean the resultant force acting on an object is equal to the derivative of the linear momentum of the object with respect to time.
    
Third Law: action and reaction force of two objects have the same magnitude, the direction reversed, and the line. This means that if an object A, which gives a force of F on object B, then object B will give a force of-F to object A. F and-F have the same magnitude but different direction. This law is also known as the action-reaction law, with F called the action and-F is a reaction.The three laws of motion was first summarized by Isaac Newton in his Philosophiae Naturalis Principia Mathematica, first published on July 5, 1687. Newton used his work to explain and investigate the motion of a variety of physical objects and systems. For example, in the third volume of the text, Newton showed that the laws of motion combines with the general law of gravity, he can explain Kepler's laws of planetary movements belong.

 
Newton's first law



Law I: Every body will maintain a state of rest or moving uniformly straight, unless there is a force acting to change it.This law states that if the resultant force (the vector sum of all forces acting on the body) is zero, then the velocity is constant. Mathematically formulated to be:
\sum \mathbf{F} = 0 \Rightarrow \frac{d \mathbf{v} }{dt} = 0.
Meaning:

    
An object is stationary will remain stationary unless there is a non-zero resultant force acting on it.
    
An object is moving, it will not change speed unless there are non-zero resultant force acting on it.Newton's first law is the law of inertia explanation of the return that has been described by Galileo. In his book, Newton pays tribute to Galileo for this law. Aristotle argued that each object having an origin in the universe: a heavy object such as a stone would be on the ground and light objects like smoke in the sky. The stars will remain in heaven. He thought that an object is at its natural condition if it does not move, and for an object moving in a straight line at constant speed needed something from the outside that kept pushing the object, otherwise the object will stop moving. But Galileo realized that force is needed to change the speed of the object (acceleration), but speed is not necessary to maintain the style. Same with Newton's first law: Without force means no acceleration, then the object is at a constant speed.

 


Newton's second lawThe second law states that the total force on a particle is equal to the number of linear momentum p changes with time:
\mathbf{F} = \frac{\mathrm{d}\mathbf{p}}{\mathrm{d}t} = \frac{\mathrm{d}(m\mathbf v)}{\mathrm{d}t},
Because the law only applies to systems with constant mass, the mass variable (a constant) can be excluded from the differential operator using the rules of differentiation. Thus,
\mathbf{F} = m\,\frac{\mathrm{d}\mathbf{v}}{\mathrm{d}t} = m\mathbf{a},
With F is the total force acting, m is the mass of the object, and a is the acceleration of the object. The total force acting on a body produces a proportional acceleration.Increases or decreases the mass of the system will result in a change in momentum. Change of momentum is not the result of force. To calculate the mass of the system can change, it takes a different equation.In accordance with the first law, the time derivative of momentum is not zero when there is a change of direction, although no change of scale. An example is the uniform circular motion. This relationship also implies the conservation of momentum: When the resultant force acting on the object is zero, the momentum of the object is constant. Any change in the style proportional to the change in momentum per unit time.This second law needs to change if special relativity into account, because the speed is very high yield masses at speeds approaching no real momentum.Impulse
Impulse J occurs when a force F acting on a time interval Δt, and is given by
 \mathbf{J} = \int_{\Delta t} \mathbf F \,\mathrm{d}t .
Impulse is a concept used to analyze the collision.Systems with changing massSystems with changing mass, such as rocket fuel is used and the rest out of gas, not termasduk in a closed system and can not be calculated by simply changing the mass becomes a function of time in the second law. The reason, as it is written in An Introduction to Mechanics Kleppner and Kolenkow works, is that Newton's second law applies to fundamental particles. In classical mechanics, a particle has a constant mass. In the case of particles in a system that clearly defined, Newton's law can be used by adding up all the particles in the system:
\mathbf{F}_{\mathrm{total}} = M\mathbf{a}_\mathrm{pm}
with Ftotal is the total force acting on the system, M is the total mass of the system, and apm is the acceleration of the center of mass of the system.Systems with varying mass like a rocket or a perforated bucket can not usually be counted as the particle system, then Newton's second law can not be used directly. The new equation is used to solve such problems by rearranging the second law and calculate the momentum carried by the mass into or out of the system:
\mathbf F + \mathbf{u} \frac{\mathrm{d} m}{\mathrm{d}t} = m {\mathrm{d} \mathbf v \over \mathrm{d}t}
with u is the velocity of the mass into or out relative to the center of mass of the main object. In some conventions, big (u dm / dt) on the left side of the equation, which is also called a boost, is defined as the force (force issued by an object in accordance with the change in mass, such as rocket boost) and be included in the size of F. So by changing the definition of acceleration, the equation had beco
\mathbf F = m \mathbf a.
HistoryNewton's second law in its original language (Latin) reads:Lex II: Mutationem motus proportionalem esse vi motrici impressae, et Fieri secundum lineam rectam qua vis illa imprimitur.Diterjmahkan quite rightly by Motte in 1729 to:

Law II: The alteration of motion is ever proportional to the motive force impress'd; and is made in the direction of the right line in roomates that force is impress'd.Which in Indonesian means:

Second Law: The change of motion is always proportional to the force generated / work, and have the same direction with the normal of the point of tangency, and object styles.

Newton's third law'
Third Law: For every action there is always an equal reaction and the opposite direction: or styles of the two objects on each other are always equal and opposite directions.
'Any object push or pull other objects having the same pressure or traction of the objects are pressed or pulled. If you press a stone with your finger, your finger is also pressed by the stone. If a horse pulling a rock using a rope, the horse is also "interested" in the direction of the stone: for rope is used, it will also draw the horse in the direction he pulled the stone by stone in the direction of the horse.The third law explains that all forces are interactions between different objects, then there is no force acting on only one thing. If object A work force on the object B, object B will simultaneously work on the same style with the object A and the second line style. As shown in the diagram, the launcher Ice (Ice skater) gives the forces on each other with the same magnitude, but opposite directions. Although given the same force, the acceleration is happening is not the same. Launchers are a smaller mass will have a greater acceleration due to Newton's second law. The two forces acting on the third law is the same type style. For example, between the wheels with street alike friction.In simple, the style is always working on a pair of objects, and never only on an object. So for every style always has two ends. Every end of the style is the same but in the opposite direction. Or a tip of the style is a reflection of the other.Mathematically, this third law in the form of a one-dimensional vector equation, which can be written as follows. Assume object A and object B exerts a force against each other.

\sum \mathbf{F}_{a,b}  = - \sum \mathbf{F}_{b,a}
WithFa, b are the forces acting on A by B, andFb, a is the forces acting on B by A.Newton used the third law to reduce the law of conservation of momentum, but with a deeper observation, conservation of momentum is the more fundamental idea (derived via Noether's theorem of relativity Galileo compared to the third law, and remain in force in case that makes Newton's third law as if no apply. example when the magnetic field has momentum, and in quantum mechanics.




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