Forces+&+Newton's+Laws


 * Forces and Newton's** **Law**

The tendency of an object to resist being moved, or if the object is moving, to resist change in speed and direction.
 * __ 1st law: __**
 * An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.**
 * -**** Inertia:

- Two examples from life: 1. (moving) While riding a bike, you fly forward of your bike when hitting a curb, which abruptly stops the motion of the bike. 2. (not moving) When you press the gas petal in your car you notice that the coffee in your mug begins to move in the opposite direction of the way you are traveling.

__2nd Law__ - N **** et force (2 definitions) - the sum of forces acting on an object ** **- Resultant Vector :a single force whose external effects on a rigid body are the same as the effects of several actual forces acting on the body.**

- ** D ** **   ifferences between weight vs. mass The mass of an object refers to the amount of matter that is contained by the object; while the weight of an object is the force of gravity acting upon that object. Weight is related to the pull of the earth on an object while mass is related to the density of an object. The mass of an object never changes, while weight can vary depending on where in the universe the object is located.

Ex. If an object with a mass of 3kg on earth was taken up to the moon it would still contain a mass of 3kg but it would weight less because gravity is not as strong on the moon.** ** __ 3rd law  __ - If two objects interact, the magnitude of the force exerted on object 1 by oject 2 is equal to the magnitude of the force simultaneously exerted on object 2 by object 1, and these two forces are opposite in direction.** **(For every action, there is an equal and opposite reaction)** The normal force is the support force exerted upon an object which is in contact with another stable object. (ex. You see a book sitting on a table. Normal force is the gravitational force exerted on the book by the table.)
 * -  Normal Force: Fnorm   **

I**n every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object __equals__ the size of the force on the second object. The direction of the force on the first object is __opposite__ to the direction of the force on the second object. **Forces always come in pairs - equal and opposite action-reaction force pairs.**
 * - Action reaction pairs

A force opposing motion. As soon as there is movement there is friction.
 * - Friction:

-** **C** **oefficient of Friction** The ratio of friction between two objects and the forces pushing them together. The coefficient of friction depends on the materials used; for example, ice on steel has a low coefficient of friction, while rubber on pavement has a high coefficient of friction.

The type of surfaces and the amount of force used to push the objects together
 * -** **Two things friction depends on?**


 * -** **Kinetic vs. Static**

Static friction
Static friction is friction between two solid objects that are not moving relative to each other. For example, static friction can prevent an object from sliding down a sloped surface. The static friction force must be overcome by an applied force before an object can move. The maximum possible friction force between two surfaces before sliding begins is the product of the coefficient of static friction and the normal force: //f// = μ//s////F////n//. When there is no sliding occurring, the friction force can have any value from zero up to //F////m////a////x//. Any force smaller than //F////m////a////x//  attempting to slide one surface over the other is opposed by a frictional force of equal magnitude and opposite direction. Any force larger than //F////m////a////x//  overcomes the force of static friction and causes sliding to occur. The instant sliding occurs, static friction is no longer applicable and kinetic friction becomes applicable. An example of static friction is the force that prevents a car wheel from slipping as it rolls on the ground. Even though the wheel is in motion, the patch of the tire in contact with the ground is stationary relative to the ground, so it is static rather than kinetic friction. (Wikipedia)

Kinetic friction
Kinetic friction occurs when two objects are moving relative to each other and rub together (like a sled on the ground). The coefficient of kinetic friction is typically denoted as //μ//k, and is usually less than the coefficient of static friction for the same materials. Kinetic friction is when two objects are rubbing against each other. Putting a book flat on a desk and moving it around is an example of kinetic friction. Or a book sliding off of a desk is another example of kinetic friction. (Wikipedia)