mechanics
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What is mechanics in physics?
In physics, mechanics studies how objects move (or don't move) when forces act on them. Classical mechanics includes kinematics, which describes motion, and dynamics, which studies how forces cause motion or static equilibrium. Isaac Newton's three laws of motion form the basis of classical mechanics.
Mechanics has three branches:
* Statics examines forces on a resting body.
* Kinematics describes a body's possible motions.
* Kinetics predicts the motion in a situation.The principles of mechanics apply to celestial bodies, ordinary objects, and atomic and subatomic phenomena.
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What is a force?
In mechanics, a force is any influence that causes an object to undergo a change in movement, direction, or shape. It is commonly explained using Newton's laws of motion. A body at rest or in uniform motion stays that way unless a force acts on it. When a force acts on a body, it accelerates in the direction of the force. Every action has an equal and opposite reaction.
Force is measured using the newton, the standard unit in the International System. Itâs the force required to accelerate one kilogram by one meter per second squared.
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What are Newton's three laws of motion?
Isaac Newton, an English physicist and mathematician, introduced his three laws of motion, which form the basis of classical mechanics. These laws explain the relationship between a body's motion and the forces acting upon it.
Newton's laws of motion:
1. First law (law of inertia) A body remains at rest or in uniform motion in a straight line unless acted upon by a force.
2. Second law The change of motion (momentum) of an object is proportional to the force impressed and occurs in the direction of the force. This law is often expressed as the equation (F = ma), where F is the force, m is the mass, and a is the acceleration.
3. Third law To every action, there is always an equal and opposite reaction.5 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does friction affect movement?
Friction is a force that resists the sliding or rolling of one solid object over another. It opposes motion and can be both beneficial and detrimental. For example, friction is needed for walking and gripping objects, but it also consumes about 20% of an automobile's engine power.
The amount of friction is nearly independent of the contact area but is proportional to the load pressing the surfaces together. The frictional force is directed oppositely to the motion of the object.
Kinetic friction arises between surfaces in relative motion, while static friction acts between surfaces at rest. Rolling friction occurs when a wheel rolls over a surface. Coefficients of sliding friction are generally greater than coefficients of rolling friction.
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What is work in physics, and how is it calculated?
In physics, work is the measure of energy transfer when an object is moved over a distance by an external force, with at least a part of the force applied along the displacement direction. When the force is constant, work ( W) is calculated by multiplying the length of the path by the component of the force (f) acting along the path or distance (d).
The equation can be expressed as (W = fd). If the force is exerted at an angle (\theta) to the displacement, the work done is (W = fd \cos \theta).
Work done on a body equates to the increase in its energy. However, if the applied force opposes the object's motion, the work is negative, meaning energy is taken from the object.
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How does the law of conservation of energy apply to mechanics?
The law of conservation of energy states that in a closed system, the total energy remains constant, though it may transform between forms. In mechanics, this principle is seen in the interconversion of kinetic and potential energy. For instance, a pendulum's energy shifts from kinetic (motion) to potential (stored) as it swings upwards, but the total sum remains constant, disregarding friction.
When a block slides down a slope, potential energy converts to kinetic energy. Friction, however, can convert some of this energy into thermal energy, but the total energy is still conserved because it changes form rather than being lost. This principle extends to various forms of energy, including chemical, electrical, and magnetic energy.
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mechanics, science concerned with the motion of bodies under the action of forces, including the special case in which a body remains at rest. Of first concern in the problem of motion are the forces that bodies exert on one another. This leads to the study of such topics as gravity, electricity, and magnetism, according to the nature of the forces involved. Given the forces, one can seek the manner in which bodies move under the action of forces; this is the subject matter of mechanics proper.
Historically, mechanics was among the first of the exact sciences to be developed. Its internal beauty as a mathematical discipline and its early remarkable success in accounting in quantitative detail for the motions of the Moon, Earth, and other planetary bodies had enormous influence on philosophical thought and provided impetus for the systematic development of science.
Mechanics may be divided into three branches: statics, which deals with forces acting on and in a body at rest; kinematics, which describes the possible motions of a body or system of bodies; and kinetics, which attempts to explain or predict the motion that will occur in a given situation. Alternatively, mechanics may be divided according to the kind of system studied. The simplest mechanical system is the particle, defined as a body so small that its shape and internal structure are of no consequence in the given problem. More complicated is the motion of a system of two or more particles that exert forces on one another and possibly undergo forces exerted by bodies outside of the system.
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The principles of mechanics have been applied to three general realms of phenomena. The motions of such celestial bodies as stars, planets, and satellites can be predicted with great accuracy thousands of years before they occur. (The theory of relativity predicts some deviations from the motion according to classical, or Newtonian, mechanics; however, these are so small as to be observable only with very accurate techniques, except in problems involving all or a large portion of the detectable universe.) As the second realm, ordinary objects on Earth down to microscopic size (moving at speeds much lower than that of light) are properly described by classical mechanics without significant corrections. The engineer who designs bridges or aircraft may use the Newtonian laws of classical mechanics with confidence, even though the forces may be very complicated, and the calculations lack the beautiful simplicity of celestial mechanics. The third realm of phenomena comprises the behaviour of matter and electromagnetic radiation on the atomic and subatomic scale. Although there were some limited early successes in describing the behaviour of atoms in terms of classical mechanics, these phenomena are properly treated in quantum mechanics.
Classical mechanics deals with the motion of bodies under the influence of forces or with the equilibrium of bodies when all forces are balanced. The subject may be thought of as the elaboration and application of basic postulates first enunciated by Isaac Newton in his Philosophiae Naturalis Principia Mathematica (1687), commonly known as the Principia. These postulates, called Newtonâs laws of motion, are set forth below. They may be used to predict with great precision a wide variety of phenomena ranging from the motion of individual particles to the interactions of highly complex systems. A variety of these applications are discussed in this article.
In the framework of modern physics, classical mechanics can be understood to be an approximation arising out of the more profound laws of quantum mechanics and the theory of relativity. However, that view of the subjectâs place greatly undervalues its importance in forming the context, language, and intuition of modern science and scientists. Our present-day view of the world and manâs place in it is firmly rooted in classical mechanics. Moreover, many ideas and results of classical mechanics survive and play an important part in the new physics.
The central concepts in classical mechanics are force, mass, and motion. Neither force nor mass is very clearly defined by Newton, and both have been the subject of much philosophical speculation since Newton. Both of them are best known by their effects. Mass is a measure of the tendency of a body to resist changes in its state of motion. Forces, on the other hand, accelerate bodies, which is to say, they change the state of motion of bodies to which they are applied. The interplay of these effects is the principal theme of classical mechanics.
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Although Newtonâs laws focus attention on force and mass, three other quantities take on special importance because their total amount never changes. These three quantities are energy, (linear) momentum, and angular momentum. Any one of these can be shifted from one body or system of bodies to another. In addition, energy may change form while associated with a single system, appearing as kinetic energy, the energy of motion; potential energy, the energy of position; heat, or internal energy, associated with the random motions of the atoms or molecules composing any real body; or any combination of the three. Nevertheless, the total energy, momentum, and angular momentum in the universe never changes. This fact is expressed in physics by saying that energy, momentum, and angular momentum are conserved. These three conservation laws arise out of Newtonâs laws, but Newton himself did not express them. They had to be discovered later.
It is a remarkable fact that, although Newtonâs laws are no longer considered to be fundamental, nor even exactly correct, the three conservation laws derived from Newtonâs lawsâthe conservation of energy, momentum, and angular momentumâremain exactly true even in quantum mechanics and relativity. In fact, in modern physics, force is no longer a central concept, and mass is only one of a number of attributes of matter. Energy, momentum, and angular momentum, however, still firmly hold centre stage. The continuing importance of these ideas inherited from classical mechanics may help to explain why this subject retains such great importance in science today.