Unit+3+Energy+and+Conservation+of+Energy

**Unit 3: Energy and Conservation of Energy**
__Notes by Melissa Quinn__
 * Nov. 11**
 * __UNIVERSAL GRAVITATION__**

__Key Concepts__
 * The formula for universal gravitation was determined by Sir Isaac Newton
 * It is [[image:http://upload.wikimedia.org/wikipedia/en/math/0/f/3/0f36df929ac9d711a8ba8c5658c3bfee.png caption="F = G frac{m_1 m_2}{r^2} "]]
 * Where G is a constant that equals 6.67 X 10^ -11
 * m1 and m2 are the mass of the two objects being considered
 * r is the distance between these two objects
 * As the distance between the two objects increases the size of the force of gravity gets increasingly smaller ( follows the inverse square law)
 * Fg can never equal 0 and can never be negative because the Earth's gravitational force extends an infinite distance to the universe
 * All objects in our solar system exert a force of gravity on the earth but they are so far away that it has no effect

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 * The formula for centripetal acceleration is :


 * Earth's gravity is always pulling objects inwards
 * Therefore objects in orbit don't fall straight down because objects have inertia so they want to continue in their current path of motion
 * So when they fall out of orbit they don't immediately fall at the same time

__Notes by Melissa Quinn__
 * Nov. 18**
 * __FORCES QUIZ__**


 * today in class we had our forces quiz
 * The quiz consisted of forces questions dealing with objects not in motion, objects moving in parallel directions, and objects on an inclined surface
 * for each of these types of questions the following formulas and concepts were needed:
 * sum of the forces = mass x acceleration
 * Fg = m x a ( force of gravity = mass x acceleration )
 * if an object isn't moving than than the sum of the forces acting in the parallel direction - the sum of the forces in the perpendicular direction will equal 0
 * it is necessary to break the vector diagram into components and solve ( especially when the object is on an inclined plane)
 * the only change from the flat surface is that gravity becomes a component. The normal force ( FN) remains perpendicular to the object
 * if a tension question is provided you solve for acceleration using THE WHOLE SYSTEM first. you then solve for the individual tensions using the specific masses involved.
 * Tension = ma + Fr ( tension is mass multiplied by acceleration plus the force of friction)
 * if there is a tension question when the object is suspended you can solve by using components OR by a closed vector diagram
 * it will be static equilibrium because it will be hanging and therefore not moving

__Notes by Melissa Quinn__
 * Nov. 25**
 * __MOMENTUM__**

* helpful link : http://www.physics247.com/physics-help/momentum.shtml
 * Momentum : a measure of an object's tendency to move in a straight line with constant speed. It is the product of mass and velocity. In as much as velocity is relative, momentum depends on the frame of reference used to observe events.
 * to solve momentum problems using the component method you draw a vector diagram of the 2 masses
 * you then use conservation of energy ( sum of the forces in the parallel direction = the sum of the forces in the perpendicular direction
 * 2-D collisions
 * to solve these problems you draw a vector diagram of the objects
 * the vector diagrams for initial and final momentum will give the total momentum because momentum is always   conserved
 * P1= P2
 * m1v1= m2v2
 * P1 + P 2 = PT ( total momentum )