Ball Bearings

external image ball-bearing.jpg external image images?q=tbn:ANd9GcQS8JgKhGk9LZZdQswKMFBtXMTBzHZI7CT1BOxnsT3IhOJ7XdIi

external image images?q=tbn:ANd9GcQ7EBkvjHk2zyJV_kQYHh_Ar_lzCB-vcMdxHsAySk4bd_Hd4gnAJw
Leonardo Da Vinci's ball bearing machine model
Leonardo Da Vinci's ball bearing machine model

Newton to grams:

1N = 100g

Definitions for Force:
1) Force is a push or pull
2) Force is the capacity to do work or cause physical change
3) Force= Mass times acceleration (F = ma)
4) A force is that which changes or tends to change the state of rest or motion of a body.
Examples:
For simplicity sake, all forces (interactions) between objects can be placed into two broad categories: contact forces, and forces resulting from action-at-a-distance.
Contact Forces include: frictional forces, buoyant forces, normal forces, and air resistance forces
Action-at-a-distance forces include: gravitation, electrostatic and magnetic forces.
Measuring Force:
Force is measured using either the English System of Measurements or the International System of Units (SI).
Common Units of Force
--->>SI: Newton (N) 1 N = 0.225 lb;
One Newton (N) of force is defined as the amount of force needed to accelerate 1 kilogram (kg) of mass at a rate of 1 meter per second squared (m/s2).
1 Newton = 1 kg m/sec2 (A kilogram is the amount of weight at which 1 N of force will accelerate at a rate of 1 m/s2.)
--->>English System: Pound (LB) 1 LB = 4.448 N
In English system of measurements, a slug is the amount of mass that 1 pound of force will accelerate at 1 ft/s2, and a pound mass is the amount of mass that 1 LB of force will accelerate at 32 feet/s2.

Friction is a force that acts between two objects. It has two different types, one allowing a moving object to stop, one allowing a stationary object to remain still. Here are some examples of both frictions in action:

..We are able to sit in a chair and not slide out because friction keeps us put.
..If I slide a ruler across a table friction will allow it to stop.

Type of forces:
- gravitational force
- elastic spring force
- magnetic force
- fritional force

References:
A complete guide to psle by rajeswarik.
http://wiki.answers.com/Q/What_is_friction
http://www.edinformatics.com/math_science/force.htm



Force


From Wikipedia, the free encyclopedia (Redirected from Forces)See also Force (disambiguation).external image 290px-Force_examples.svg.pngexternal image magnify-clip.pngForces are also described as a push or pull on an object. They can be due to phenomena such as gravity,magnetism, or anything that might cause a mass to accelerate.

Classical mechanics
mathbf{F} = frac{mathrm{d}}{mathrm{d}t}(m mathbf{v})
mathbf{F} = frac{mathrm{d}}{mathrm{d}t}(m mathbf{v})

Newton's Second Law
History of classical mechanics·Timeline of classical mechanics
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In physics, a force is any influence that causes a free body to undergo a change in speed, a change in direction, or a change in shape. Force can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., toaccelerate, or which can cause a flexible object to deform. A force has bothmagnitude and direction, making it a vector quantity. Newton's second law, F=ma, can be formulated to state that an object with a constant mass will accelerate in proportion to the net force acting upon and in inverse proportion to its mass, an approximation which breaks down near the speed of light. Newton's original formulation is exact, and does not break down: this version states that the net force acting upon an object is equal to the rate at which its momentum changes.[1] Related concepts to accelerating forces include thrust, increasing the velocity of the object, drag, decreasing the velocity of any object, and torque, causing changes in rotational speed about an axis. Forces which do not act uniformly on all parts of a body will also cause mechanical stresses,[2] a technical term for influences which cause deformation of matter. While mechanical stress can remain embedded in a solid object, gradually deforming it, mechanical stress in a fluid determines changes in its pressure and volume.[3][4] Philosophers in antiquity used the concept of force in the study of stationary andmoving objects and simple machines, but thinkers such as Aristotle and Archimedesretained fundamental errors in understanding force. In part this was due to an incomplete understanding of the sometimes non-obvious force of friction, and a consequently inadequate view of the nature of natural motion[5] A fundamental error was the belief that a force is required to maintain motion, even at a constant velocity. Most of the previous misunderstandings about motion and force were eventually corrected by Sir Isaac Newton; with his mathematical insight, he formulated laws of motion that remained unchanged for nearly three hundred years.[4] By the early 20th century, Einstein developed atheory of relativity that correctly predicted the action of forces on objects with increasing momenta near the speed of light, and also provided insight into the forces produced by gravitation and inertia. With modern insights into quantum mechanics and technology that can accelerate particles close to the speed of light, particle physics has devised a Standard Model to describe forces between particles smaller than atoms. The Standard Model predicts that exchanged particles called gauge bosons are the fundamental means by which forces are emitted and absorbed. Only four main interactions are known: in order of decreasing strength, they are: strong, electromagnetic, weak, and gravitational.[3] High-energy particle physics observations made during the 1970s and 1980s confirmed that the weak and electromagnetic forces are expressions of a more fundamental electroweak interaction.[6]


Teacher:
Student:
A force is not an act or a tangible thing, or a property of an object. A force is an interaction between two objects. It is correct that the act of pushing involves a force, but the act itself is not the force.
Beginning a discussion on force by describing the concept as an interaction may result in a different exchange between teacher and student:

Fundamental Concepts of Force

When we push or pull on a body, we are said to exert a force on it. Forces can also be exerted by inanimate objects. For example, a locomotive exerts a force on a train it is pulling or pushing.
Similarly, compressed air in a container exerts a force on the wall of the container.
The force may produce motion of the body or may cause the body to deform. Energy may be expended in the process, or the applied force may be balanced by an opposing force so that no energy is expended.
The distortion or the displacement that occurs when a body is subjected to a force occurs in accordance with Hooke's and Newton's laws governing the behavior of elastic and non-elastic bodies.
The distortion or the displacement that occurs when a body is subjected to a force occurs in accordance with Hooke's and Newton's laws governing the behavior of elastic and non-elastic bodies.

Sir Isaac Newton (1642-1727) was the first to state the basic laws of motion of bodies. He postulated three fundamental principles:
    • First Law: A body remains at rest or continues to move in a straight line with uniform velocity if there is no unbalanced force acting on it.
    • Second Law: An unbalanced force acting on a body will cause that body to accelerate in the direction of the force with an acceleration inversely proportional to the mass of the body.
    • Third Law: For every action there is an equal and opposite reaction.
References:
ilovephysics.com
http://www.nist.gov/pml/div681/grp15/whatis-force.cfm

.
In science. force, usually means a push or a pull.
external image tenpin2.jpg
Think of a game of ten pin bowling. The moving object - the ball, exerts a pushing force against anything it hits - the ten pins.
external image tugrope.jpg
Think of tugging on a rope. The person in the picture is exerting a pulling force on his end of the rope.
References:
http://www.zephyrus.co.uk/forces1.html