Ch+4+-+Laws+of+Motion

Force: a vector, is the "push or pull" on an object, two types: =Newton's Three Laws=
 * Contact - in physical contact with object it pushes
 * Field - area or region where a force acts

2. Law of Acceleration 3. Law of Interactions **
 * 1. Law on Inertia

**Newton's First Law:**
Law on Inertia 

By Definition: "A body at rest will remain at rest and a body in motion will remain in motion at a **constant velocity ** unless acted upon by an unbalanced external force."

In Other Words: If an object is chillin' it wants to stay chillin', otherwise it will keep on keeping on. media type="file" key="Newton's 1st Law.mov" width="340" height="340" Inertia- an objects unwillingness to change
 * Big masses resist changing their motion more than smaller masses.

**Newton's Second Law:**
Law of Acceleration 


 * Definition:** "The acceleration produced by a net force on a body is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the body."


 * In Other Words:** If the acceleration gets bigger than the displacement gets bigger, if mass gets bigger than the acceleration gets smaller. The opposite also applies.


 * New equations:** F = ma, with force and acceleration in the same direction. a∞F, acceleration an force are directly proportional. a ∞ 1/m, acceleration and mass are indirectly proportional.


 * Freebody Diagrams (Forces):** Types of forces include Tension, Gravitational(Weight), Normal(upward support force from surface and it is perpendicular to the surface), and Friction(opposite the direction the object is moving).


 * Law of Universal Gravitation:**Every body attracts every other body in the universe with a force that is directly proportional to the product of the masses and inversely proportional to the square of the separation of their centers.


 * Equations:**Fg ∞ m1m2, Fg ∞ 1/r^2, W=mg...weight is eqaul to the force of gravity..as an object falls gravity is the only force acting upon it.



media type="file" key="acceleration2.m4v" width="348" height="348"

Example Problems:
Object 1 has a mass of //m//1 = 4.00 kg, object 1 is sitting on a frictionless table completely horizontal and is connected through a cable that is ober a pulley that is frictionless to the second object with the mass of 12.0 kg. find the amount of acceleration of both objects.

Force of Gravity = weight W = mg always points down(towards the center of the planet)

Law of Interactions 
 * Newton's Third Law:**


 * Definition:** "For every force on one body, there is an equal (in magnitude) and opposite (in direction) force on another body."


 * In Other Words:** For every action there is an opposite and equal reaction.

media type="file" key="Newton's 3rd Law.mov" width="321" height="321"

Forces will always come in pairs, equal and opposite action-reaction forces.

(The pencil is applying the same force down on the the deck of cards, that the cards are applying up onto the pencil. The forces are equal in opposite directions because the pencil doesn't fly upward and the cards don't crush under the pencil.)

Applying the 3rd Law
Bugs on Windshield Cars on the Road Tail Wagging the Dog Bullet in a Gun

static vs. kinetic friction brought to you by msn images -resistance to motion between two points -parallel but opposite to motion
 * FRICTION**
 * Force of Friction**

-static(object is not moving because of friction) -sliding or kinetic -rolling
 * Types of Friction**

-Normal Force (usually equal to weight) -Surfaces involved- coefficient of friction (the rougher the surface the more friction is created)
 * What affects the force of friction?**

__Coefficient of Friction__ µ-no units the greater the µ, the greater the friction

F = µN (FUN)

Finding the Normal Force - Level Surface Horizontal Forces do not impact the normal force Object Moving with Constant Velocity ∑F = 0

T-µk-m1g = m1a V² = Vo² + 2xg V = Vo + at
 * Other Equations:**

To Solve the Problems 1. Draw Freebody Diagrams 2. Write Sum of Forces 3. Sum of forces = 0 4. Sum of forces = ma Need to be done in x and y directions Look at what is known and unknown for possible solutions Force on the hill, use sine and cosine