Science Project

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PROJECT DONE BY - GAUTAM FRICTION

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FRICTION

INTRODUCTION ON FRICTION : 

INTRODUCTION ON FRICTION Friction is the force resisting the relative lateral (tangential) motion of solid surfaces, fluid layers, or material elements in contact.

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Friction occurs in part because rough surfaces tend to catch on one another as they slide past each other. Even surfaces that are apparently smooth can be rough at the microscopic level. They have many ridges and grooves. The ridges of each surface can get stuck in the grooves of the other, effectively creating a type of mechanical bond, or glue, between the surfaces. CAUSES OF FRICTION

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Different kinds of motion give rise to different types of friction between objects. Static friction occurs between stationary objects, while sliding friction occurs between objects as they slide against each other. Other types of friction include rolling friction and fluid friction. The coefficient of friction for two materials may differ depending on the type of friction involved. DIFFERENT KINDS OF FRICTION

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Static friction prevents an object from moving against a surface. It is the force that keeps a book from sliding off a desk, even when the desk is slightly tilted, and that allows you to pick up an object without the object slipping through your fingers. In order to move something, you must first overcome the force of static friction between the object and the surface on which it is resting. This force depends on the coefficient of static friction (µs) between the object and the surface and the normal force (N) of the object. STACTIC FRICTION

PICTURE OF STACTIC FRICTION : 

PICTURE OF STACTIC FRICTION

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A book sliding off a desk or brakes slowing down a wheel are both examples of sliding friction, also called kinetic friction. Sliding friction acts in the direction opposite the direction of motion. It prevents the book or wheel from moving as fast as it would without friction. When sliding friction is acting, another force must be present to keep an object moving. In the case of a book sliding off a desk, this force is gravity. The force of kinetic friction depends on the coefficient of kinetic friction between the object and the surface on which it is moving (µk) and the normal force (N) of the object. For any pair of objects, the coefficient of kinetic friction is usually less than the coefficient of static friction. This means that it takes more force to start a book sliding than it does to keep the book sliding. KINETIC FRICTION

PICTURE OF KINETIC FRICTION : 

PICTURE OF KINETIC FRICTION

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Dry friction resists relative lateral motion of two solid surfaces in contact. Dry friction is also subdivided into static friction between non-moving surfaces, and kinetic friction (sometimes called sliding friction or dynamic friction) between moving surfaces. DRY FRICTION

PICTURE OF DRY FRICTION : 

PICTURE OF DRY FRICTION

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Rolling friction hinders the motion of an object rolling along a surface. Rolling friction slows down a ball rolling on a basketball court or softball field, and it slows down the motion of a tire rolling along the ground. Another force must be present to keep an object rolling. For example, a pedaling bicyclist provides the force necessary to the keep a bike in motion. Rolling friction depends on the coefficient of rolling friction between the two materials (µr) and the normal force (N) of the object. The coefficient of rolling friction is usually about t that of sliding friction. Wheels and other round objects will roll along the ground much more easily than they will slide along it. ROLLING FRICTION

PICTURE OF ROLLING FRICTION : 

PICTURE OF ROLLING FRICTION

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Lubricated friction or fluid friction resists relative lateral motion of two solid surfaces separated by a layer of gas or liquid LUBRICATED FRICTION

PICTURE OF LUBRICATED FRICTION : 

PICTURE OF LUBRICATED FRICTION

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Fluid friction is also used to describe the friction between layers within a fluid that are moving relative to each other FLUID FRICTION

PICTURE OF FLUID FRICTION : 

PICTURE OF FLUID FRICTION

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Skin friction is a component of drag, the force resisting the motion of a solid body through a fluid. SKIN FRICTION

PICTURE OF SKIN FRICTION : 

PICTURE OF SKIN FRICTION

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Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation INTERNAL FRICTION

PICTURE OF INTERNAL FRICTION : 

PICTURE OF INTERNAL FRICTION

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FORCE

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A force is a push or pull that can cause an object with mass to change itsvelocity.  Force has both magnitude anddirection, making it a vector quantity.  Newton's second law states that an object with a constant mass will accelerate in proportion to the net force acting upon and in inverse proportion to its mass. Equivalently, the net force on an object equals the rate at which its momentum changes. INTRODUCTION ON FORCE

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Forces are often described as pushes or pulls. They can be due to phenomena such as gravity, magnetism, or anything else that causes a mass to accelerate. FORCE

A PICTURE OF FORCE : 

A PICTURE OF FORCE

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Since forces are perceived as pushes or pulls, this can provide an intuitive understanding for describing forces. As with other physical concepts (e.g. temperature), the intuitive understanding of forces is quantified using precise operational definitions that are consistent with direct observations and compared to a standard measurement scale. Through experimentation, it is determined that laboratory measurements of forces are fully consistent with the conceptual definition of force offered by Newtonian mechanics. DISCRIPTIONS

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Equilibrium occurs when the resultant force acting on a point particle is zero (that is, the vector sum of all forces is zero). When dealing with an extense body, it is also necessary that the net torque in it is 0. There are two kinds of equilibrium: static equilibrium and dynamic equilibrium. Equilibria

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Static equilibrium was understood well before the invention of classical mechanics. Objects which are at rest have zero net force acting on them. The simplest case of static equilibrium occurs when two forces are equal in magnitude but opposite in direction. For example, an object on a level surface is pulled (attracted) downward toward the center of the Earth by the force of gravity. At the same time, surface forces resist the downward force with equal upward force (called the normal force). The situation is one of zero net force and no acceleration. STATIC EQUILIBRIUM

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Dynamical equilibrium was first described by Galileo who noticed that certain assumptions of Aristotelian physics were contradicted by observations and logic. Galileo realized that simple velocity additiondemands that the concept of an "absolute rest frame" did not exist. DYNAMICAL EQUILIBRIUM

GALELIO : 

GALELIO Galileo Galilei was the first to point out the inherent contradictions contained in Aristotle's description of forces.

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The electrostatic force was first described in 1784 by Coulomb as a force which existed intrinsically between two charges. The properties of the electrostatic force were that it varied as an inverse square law directed in the radial direction, was both attractive and repulsive (there was intrinsic polarity), was independent of the mass of the charged objects, and followed the law of superposition. Coulomb's Law unifies all these observations into one succinct statement. ELECTROMAGNETIC FORCES

COULOMB : 

COULOMB

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There are two "nuclear forces" which today are usually described as interactions that take place in quantum theories of particle physics. The strong nuclear force[38] is the force responsible for the structural integrity of atomic nuclei while the weak nuclear force[39] is responsible for the decay of certainnucleons into leptons and other types of hadrons.[3] NUCLEAR FORCES

PICTURE OF ELECTRO MAGNETIC & NUCLEAR FORCES : 

PICTURE OF ELECTRO MAGNETIC & NUCLEAR FORCES ELECTRO MAGNETIC FORCE NUCLEAR FORCE

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Some forces are consequences of fundamental. In such situations, idealized models can be utilized to gain physical insight. NON-FUNDAMENTAL FORCES

NORMAL FORCE : 

NORMAL FORCE The normal force is the repulsive force of interaction between atoms at close contact. When their electron clouds overlap, Pauli repulsion (due to fermionicnature of electrons) follows resulting in the force which acts normal to the surface interface between two objects.[41] The normal force, for example, is responsible for the structural integrity of tables and floors as well as being the force that responds whenever an external force pushes on a solid object. An example of the normal force in action is the impact force on an object crashing into an immobile surface

PICTURE OF NORMAL FORCE : 

PICTURE OF NORMAL FORCE

ELASTIC FORCE : 

ELASTIC FORCE An elastic force acts to return a spring to its natural length. An ideal spring is taken to be mass less, frictionless, unbreakable, and infinitely stretchable. Such springs exert forces that push when contracted, or pull when extended, in proportion to the displacement of the spring from its equilibrium position.[44] This linear relationship was described by Robert Hooke in 1676, for whom Hooke's law is named.

ROBERT HOOKE : 

ROBERT HOOKE

PICTURE OF ELASTIC FORCE : 

PICTURE OF ELASTIC FORCE

Centripetal force : 

Centripetal force For an object accelerating in circular motion, the unbalanced force acting on the object equals:

PICTURE OF CENTRIPETAL FORCE : 

PICTURE OF CENTRIPETAL FORCE

Conservative forces : 

Conservative forces A conservative force that acts on a closed system has an associated mechanical work that allows energy to convert only between kinetic or potential forms. This means that for a closed system, the netmechanical energy is conserved whenever a conservative force acts on the system. The force, therefore, is related directly to the difference in potential energy between two different locations in space,[51] and can be considered to be an artifact of the potential field in the same way that the direction and amount of a flow of water can be considered to be an artifact of the contour map of the elevation of an area

PICTURE OF CONSERVATIVE FORCE : 

PICTURE OF CONSERVATIVE FORCE

Nonconservative forces : 

Nonconservative forces For certain physical scenarios, it is impossible to model forces as being due to gradient of potentials. This is often due to macrophysical considerations which yield forces as arising from a macroscopic statistical average of microstates. For example, friction is caused by the gradients of numerous electrostatic potentials between the atoms, but manifests as a force model which is independent of any macroscale position vector. Nonconservative forces other than friction include other contact forces,tension, compression, and drag. However, for any sufficiently detailed description, all these forces are the results of conservative ones since each of these macroscopic forces are the net results of the gradients of microscopic potentials

PICTURE OF NON-CONSERVATIVE FORCE : 

PICTURE OF NON-CONSERVATIVE FORCE

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PRESSURE

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INTRODUCTION ON PRESSURE Pressure (symbol: p or sometimes P) is the force per unit area applied to an object in a direction perpendicular to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.

Negative pressures : 

Negative pressures While pressures are generally positive, there are several situations in which negative pressures may be encountered: When dealing in relative (gauge) pressures. For instance, an absolute pressure of 80 kPa may be described as a gauge pressure of -21 kPa (i.e., 21 kPa below an atmospheric pressure of 101 kPa). When attractive forces (e.g., Van der Waals forces) between the particles of a fluid exceed repulsive forces. Such scenarios are generally unstable since the particles will move closer together until repulsive forces balance attractive forces. Negative pressure exists in the transpiration pull of plants. The Casimir effect can create a small attractive force due to interactions with vacuum energy; this force is sometimes termed 'vacuum pressure' (not to be confused with the negative gauge pressure of a vacuum). Depending on how the orientation of a surface is chosen, the same distribution of forces may be described either as a positive pressure along one surface normal, or as a negative pressure acting along the opposite surface normal. In the cosmological constant.

PICTURE OF NEGATIVE PRESSURE : 

PICTURE OF NEGATIVE PRESSURE

SURFACE PRESSURE : 

SURFACE PRESSURE There is a two-dimensional analog of pressure – the lateral force per unit length applied on a line perpendicular to the force. Surface pressure is denoted by p and shares many similar properties with three-dimensional pressure.

PICTURE OF SURFACE FORCE : 

PICTURE OF SURFACE FORCE

ATMOSPHERIC PRESSURE : 

ATMOSPHERIC PRESSURE Atmospheric pressure is sometimes defined as the force per unit area exerted against a surface by the weight of air above that surface at any given point in the Earth's atmosphere. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of airabove the measurement point. Low pressure areas have less atmospheric mass above their location, whereas high pressure areas have more atmospheric mass above their location. Similarly, as elevationincreases there is less overlying atmospheric mass, so that pressure decreases with increasing elevation

PICTURE OF ATMOSPHERIC PRESSURE : 

PICTURE OF ATMOSPHERIC PRESSURE

THE END : 

THE END

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THE END