Viviana's+Page;D

**//__Circular Motion __//**
= the movement of an object at constant speed around a circle with a rixed radius.

__Axis__- Straight line around which rotation take place. __Rotation__- Object turns around an internal axis. Ex: Ice Skater __Revolution__- Object turns on an external axis. Ex: Earth around the Sun

__**Rotational Speed**__

__Linear Speed__- Distance/Time __Tangential Speed__- Speed along a circular path. __Rotational Speed__- Number of rotations per unit of time. Ex: Carousel horses travel at same rotational speed, but different tangential speed.

__**Linking Tangential & Rotational**__

Tangential speed is radial distance times time rotational speed.

= force that causes an object to follow a circular path F ﻿net =mv 2 /r
 * __Centripetal Speed__**

= always points towards the center if the circular motion.
 * __Centripetal Accleration__**

__Period__ (T)= time needed for an object to make one complete revolution. __Distanced Traveled__= Circumference

Centripetal Acceleration equals the velocity squared divided by the radius. A c ﻿ =v 2 /r

The number of revolutions equals the distance traveled by the circumference. revolutions=distance/circumference.

**//__Newton's Law of Universal Gravitation __//**
* Isaac Newton believed that gravitation forces were responsible for the acceleration of objects on the Moon and the Earth. Ex: Suppose we fire a cannon horizontally from a high mountain; the projectile will eventually fall the Earth.
 * __ Newton & Gravity __**

*Newton reasoned that if the cannon projected the cannon ball with exactly the right velocity, the projectile would travel completely around the Earth, always falling in the gravitational field but never reaching Earth.

*Newton concluded that any two objects in the Universe exert gravitational attraction on each other.

*Newton's Law of Universal Gravitational applies to ALL objects.

**__Universal Gravitation & Mass__** = a the mass of either object or both objects increases, the force of gravitational attraction increases.

As the distance separating two objects increase, the force of attraction is exponentially smaller.
 * __Universal Gravitation & Distance__**

F ﻿grav =Gm ﻿1 m ﻿2 /d ﻿2
 * __Universal Gravitation Formula__**

G= Universal Gravitation Constant G= 6.67 x 10 -11 Nm ﻿2 / kg 2

//__SAMPLE PROBLEM __// Determine the force of gravitational attraction between the Earth (m=5.98 x 10 24 kg) and a 70-kg physics student if the student is standing at sea level, a distance of 6.37 x 10 ﻿6 m from Earth's center.

__SOLUTION: __ F ﻿grav =Gm ﻿1 m ﻿2 /d ﻿2

F= (6.67 x 10 -11 ) (5.98 x 10﻿ 24 ) (70) / (6.37 x 10 6 ) 2 F= 2.79 x 10 16 / 4.06 x 10 13 F= 688N

__//**Coulomb's Laws/Electric Feilds Notes **//__
= the realtionship among electrical forces, charges and distance. It is like Newton's Law of Gravity. But unlike gravity, electric forces can attractive or repulsive.
 * __Coulomb's Law__**

F= kq ﻿ A q B /d 2

F= Force (N) K= electrical proportionality constant =9.0 x 10 9 N x M 2 / C 2 q= Charge (C for Coulomb) d= Distance (m)

The SI unit of measure for electrical charge is a Coulomb (C) Charge of 1 proton is +1.6 x 10 -19 C Charge of 1 electron is -1.6 x 10 -19 C

The charges (q) of a particle is NOT a vector quanity. Therefore, when described as "POSITIVE" or "NEGATIVE" that tells whether it is a proton or electron, but is NOT of the magnitude of the charge. DO NOT PUT THE NEGATIVES IN THE FORMULA.

= a vector quanity that relates the force exerted on a charge to the size of the charge. The magnitude of the electric field is in electric field lines.
 * __Electric Fields__**

__**Electric Field Lines**__ = the direction of arrows indicate the charge of the field. Away from a positively charged object. Toward a negatively charged object. close lines= strong field

__**Grounding**__ = touching a body to Earth to eleminate excess charge.

__**Electric Current**__ = flow of charged particles

__**Electrical Energy Sources**__ Voltaic or galvanic cells (dry) converts chemical energy to electrical energy. A series of voltaic or galvanic cells connected together is called a battery. Photovoltiac cells change solar energy into electrical energy. Generators converts kinetic energy into electrical energy.
 * Current always flows from a higher potential difference (voltage) to a lower potential difference
 * The flow will stop when the potentail difference is zero.
 * For current to continue to flow, an electrical source is needed.