1_Force

Annotations:

• The resistance that a surface or object encounters when moving over another.

1. Sliding Friction

   Annotations:

   • The friction between two objects that are in sliding contact. Also known as kinetic friction.
2. Static Friction

   Annotations:

   • Friction between two or more solid objects that are not moving relative to each other.
3. Fluid Friction

   Annotations:

   • Occurs between layers within a fluid are moving relative to each other.
4. Rolling Friction

   Annotations:

   • The force resisting the motion when a body rolls on a surface.
5. Air Resistance

   Annotations:

   • A force that is caused by air. The forces act in the opposite direction to an object moving through the air.
6. Terminal Velocity

   Annotations:

   • The constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration.

Annotations:

• Newton is a unit in the International System of Units. It is defined as a force necessary to provide a mass of one kilogram with an acceleration of one meter per second per second. One newton is equal to 100,000 dynes in the centimeter-gram-second system. The newton was names for Sir Isaac Newton, whose second law of motion describes the changes that a force can produce in the motion of a body.

Annotations:

• Gravity is described by the general theory of relativity which describes gravity, not as a force, but as a consequence of the curvature of spacetime caused by the uneven distribution of mass/energy. Gravity is well approximated by Newton's law of universal gravitation, which postulates that the gravitational force of two bodies of mass is directly proportional to the product of their message and inversely proportional to the square of the distance between them Gravity is the weakest of the four fundamental interactions of nature. The gravitational force is approximately 10-38 times the strength of the strong force, 10-36 times the strength of the electromagnetic force, and 10-29 times the strength of the weak force. As a consequence, gravity has a negligible influence on the behavior sub-atomic particles, and plays no role in determining the internal properties of everyday matter. On the other hand, gravity is the dominant force at the macroscopic scale that is the cause of the formation, shape, and trajectory of astronomical bodies, including those of asteroids, comets, planets, stars, and galaxies. It is responsible for causing the Earth and the other planets to orbit the sun; for causing the Moon to orbit the Earth; for the formation of tides; for natural convection, by which fluid flow occurs under the influence of forming stars and planets to very high temperatures; for the solar system and the galaxy forming and evolving.

1. Universal Gravity

   Annotations:

   • In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. In his own words, "I deduced that the forces which keep the planets in their orbs must [be] reciprocally as the squares of their distances from the centers about which they revolve: and thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the Earth; and found them answer pretty nearly."[3] The equation is the following: Where F is the force, m1 and m2 are the masses of the objects interacting, r is the distance between the centers of the masses and G is thegravitational constant. Newton's theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the general position of the planet, and Le Verrier's calculations are what led Johann Gottfried Galle to the discovery of Neptune. A discrepancy in Mercury's orbit pointed out flaws in Newton's theory. By the end of the 19th century, it was known that its orbit showed slight perturbations that could not be accounted for entirely under Newton's theory, but all searches for another perturbing body (such as a planet orbiting the Sun even closer than Mercury) had been fruitless. The issue was resolved in 1915 by Albert Einstein's new theory ofgeneral relativity, which accounted for the small discrepancy in Mercury's orbit. Although Newton's theory has been superseded by the Einstein's general relativity, most modern non-relativistic gravitational calculations are still made using the Newton's theory because it is simpler to work with and it gives sufficiently accurate results for most applications involving sufficiently small masses, speeds and energies.
2. Factors Affecting Gravity
3. Weight and Mass

   Annotations:

   • Mass is a measurement of how much mater is in am object.  Your mass is the same wherever you are -- on Earth, on the moon, floating in space -- because the amount of stuff you're made of doesn't change. 
   • Weight is a measurement of how hard gravity is pulling on that object. Your weight depends on how much gravity is acting on you at the moment; you'd weigh less on the moon than on earth, and in interstellar space you'd weigh almost nothing.

Annotations:

• The overall force acting on an object.

1. Balanced Forces

   Annotations:

   • Equal forces that are acting upon an object in different directions.
2. Unbalanced Forces

   Annotations:

   • Causes an object to start moving, stop, or change direction.
3. Free Fall

   Annotations:

   • A downwards movement under the force of gravity only.

Annotations:

• Any object that is cast, fired, flung, heaved, hurled, pitched,tossed, or thrown.