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toc = Definitions: = __**Circular Motion**:__ The movement of an object at constant speed around a circle with fixed radius. __**Newton and Gravity**:__ Newton concluded that any two objects in the Universe exert gravitational attraction on each other. __**Coulomb's Law**;__ = the relationship among electrical forces, charges and distances.
 * Physics **
 * Axis: Straight line around which rotation takes place.
 * Rotation: Object turns around an internal axis.
 * Revolution: Object turns around the external axis.
 * Rotational Speed: number of rotations per unit of time. Ex Carousel horses travel at same rotation speed but different trangential speed.
 * Trangential Speed: Is radical distance times the rotational speed. V=rw
 * Centripetal Force: Force that causes an object to follow a circular path.
 * Centrpental Acceleration: Always points toward the center of the circular motion.
 * Gravity: is a constant force exerted by objects that have mass.
 * Weight: is the pull of gravity
 * Universal Gravitational and Mass: As the mass of either object or both object increases, the force of gravitational attraction increase.
 * Universal Gravitational Distance: As the distance seperating two objects increase, the force of attraction is exponentially smaller.
 * Electrical Field; A vector guantity that relates the force exerted on a charge to the size of the charge. The magnitude of the electric field is measured in N/C (Newtons/Coulomb)
 * Electrical Lines: Direction of arrows indicate the charge of the lines.
 * Grounding: Touching a body to earth to eliminate excess charge.
 * Electric Current; Flow of charge particles. Current always flows from a higher potential difference (voltage) to lower potential difference. The flow will stop when the potential difference is zero.
 * Electrical Energy Source; Voltaic or galvanic cells (dry cells) converts chemical energy to electrical energy.

Explanations:
**Circular Motion**: When a car is going straight at constant speed, the forward and backward forces on it are canceling out, producing a total force of zero. When it moves in a circle at constant speed, there are three forces on it, but the forward and backward forces cancel out, so the vector sum is an inward force. 1. In the turning truck's frame of reference, the ball appears to violate Newton's laws, displaying a sideways acceleration that is not the result of a force-interaction with any other object. 2. In an inertial frame of reference, such as the frame fixed to the earth's surface, the ball obeys Newton's first law. No forces are acting on it, and it continues moving in a straight line. It is the truck that is participating in an interaction with the asphalt, the truck that accelerates as it should according to Newton's second law. In an inertial frame everything makes more sense. The ball has no force on it, and goes straight as required by Newton's first law. The truck has a force on it from the asphalt, and responds to it by accelerating (changing the direction of its velocity vector) as Newton's second law says it should. A body that travels an equal distances in equal amounts of time along a circular path has a constant speed but not constant velocity. This is because velocity is a vector and thus it has magnitude as well as direction. The velocity of P is directed along the tangent at P. The speed remains constant but the velocity has changed. We know that if the velocity changes with time then the ball on the string is accelerating as well. Carpusel horses travel at the same rotation speed but differeent tangential speed. An example of centripetal force is a rotating carnival ride. media type="custom" key="7675203"

__ **Law of Universal Gravitation** __ Most people thought that the forces causing motions on earth and the forces causing the stars and planets to move were differnet forces. Isaac Newton realized that the forces and the same laws of physics apply everywhere in the universe. So his law of gravity is called Law of Universal Gravitation. Newtons law of Universal Gravitation apllies to all objects. __ Force of Gravity: __ Newton concluded that any two objects in the universe exert gravitational attraction on each other. __ Gravitaional Force and Mass: __ The more the masses of the objects, the larger the gravitatonal force between them. Finding the gravitational force between you and Earth, which is your weight would double. If earth were to become twice as massive, without changing its size, your weight would also double. Increasing either mass, increase the gravitational force between two objects; decreasing their mass decreases the gravitational force.
 * Newton and Gravity: **

__ Gravitational Force and Distance __ As the distance between two objects gets larger, the gravitational force between them gets smaller. It never gets to zero; it just gets too small to matter. If you were suddenly suspended in space twice as far from the center of the earth as you are now the gravitational force would be one fourth as much as it is on Earth's surface. media type="custom" key="7675291"

- Inversely proportional to the square of the distance r between the particles and is directed along the line that joins them. - Proportional to the product of the charges q1 and q2. - Attracted if the charges have opposite electrical sign and repulsed if the charges have equal sign. Coulomb 's Law can be expressed in the form of an equation : The validity of Coulomb's Law has been verified with modern devices that have detected that the exponent 2 has an exactitude of one part in 1016.
 * __ Coulomb's Law: __**
 * Coulomb demonstrated that the electric force between two stationary charged particles is : **

Ke is a constant known as the Coulomb 's constant, which in the International System units has the value Ke = 8.987x109 Nm2/C2.

The International System unit for charge is the Coulomb. The smallest known charge in nature is the charge of an electron or proton, which has an absolute value of e = 1.60219x10-19 C. Thus, a 1 Coulomb charge is approximately equal to a charge of 6.24x1018 (= 1C/e) electrons or protons. We should notice that the force is a vectorial quantity, that is, has magnitude and direction. Coulomb 's Law expressed in vectorial form for the electric force F12 exerted by a charge q1 over a second charge q2 is (bold type is used to denote vectorial quantities):

As every force obeys Newton's third Law, the electric force exerted by q2 over q1 is equal in magnitude to the force exerted by q1 over q2 and in the opposite direction, that is F21= - F12. If q1 and q2 have the same sign, F12 takes the direction of r. If q1 and q2 have opposite sign, the product q1q2 is negative and F12 points opposite to r. When two or more charges are present, the force between any pair of them is given by the above equation. Hence, the resultant force on any of them is equal to the vectorial sum of the forces exerted by the different individual charges. For example, with three charges, the resultant force exerted by particles 2 and 3 over 1 is  F1 = F21 + F31

Citation:
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 * Physics notebook pages 28-35
 * www. splung .com
 * www. suite101 .com