 Force- an action that has the ability to change motion (push, pull)  Units- pounds or Newtons  1N = 1kg x 1 m/sec 2  Mass- the amount of matter in an object  Units- grams or kilograms  Mass is the same everywhere  Weight- the amount of mass with gravitational pull  Units- pounds or Newton  Weight changes due to gravity

 Motion-a change in position.  Position- where something is compared with where it started, including direction  Ex. 7km North of Building A  Distance-interval of length without regarding direction  Ex. I walked 14km  An object at rest is a special case of motion in which there is not change in position

 How can the motion of an object be changed?  Change how fast it is moving  Starting  Stopping  Changing speeds  Change its direction

How does graphing fit in? (It’s never going to go away!)  Position vs. Time graphs show where things are at a different times which makes it easy to see how things have moved.  EX: Moving AwayMoving to StartStopped

 Newton’s 1 st Law- law of inertia  An object at rest will stay at rest and an object in motion will stay in motion unless an unbalanced force is acted upon it.  Inertia- the property of an object to resist changing its state of motion.  The amount of inertia an object has depends on its mass.

 Newton’s 2 nd Law  The acceleration of an object is directly proportional to the force acting on it and inversely proportional to its mass.  Force causes acceleration  Mass resists acceleration  The acceleration you get is equal to the ratio of force over mass  a=FF=ma m

 Force isn’t necessary to keep an object in motion at constant speed.  The motion of an object depends on the total of all forces acting on the object- net force.  When forces on an object are balanced, the net force is zero=equilibrium.

 Acceleration- the rate at which something speeds up or slows down  Formula: a=V f -V i /t

How does speed fit in?  Speed-the distance an object travels divided by the time it takes  Speed is the rate of motion  Rate-ratio between two different quantities (distance/time)  Units: m/s or km/hr  Formula: V=d/tspeed=distance/time  Constant speed-the speed does not change  Instantaneous speed- the speed at a single instant of time

Graphing…another connection!  Distance vs. Time graphs show how speed changes at different places. TIme Distance

 Velocity- the speed and direction of the object.  The velocity of an object is the rate at which its position changes over time and the direction of the change.  Ex:  Speed= 220 km per hour  Velocity= 220 km per hour due north  Velocity can change even if speed remains constant (because you could change direction)

 Gravity- a force that pulls every mass toward every other mass.  Gravity depends on how much mass,  Gravity= 9.8 N or 9.8 m/sec 2  Law of Universal Gravitation- gravity is a force of attraction that exists between any two objects that have mass.  Force of attraction increase when mass increases.  Force also increases when objects get closer.

 Calculating force between two objects  G= Gravitational constant  6.67x10 11 N· m 2 /kg 2

 Weight- force created by gravity on an object.  Depends on the objects mass  Calculating  Fw= mg  (9.8 m/sec 2 )  W= mg  Units- N or lbs NOT kg

 Friction- forces that result from relative motion between objects.  Friction forces always work against the motion that produces them.  Friction is opposite whatever force is causing it.  Wear- how moving parts can erode each other  Net Force- what is left after subtracting friction force from gravity. (total force)  Friction reduces acceleration  All machines have friction

4 types of Friction  Air Friction- air moving around moving objects creates an opposing force.  Sliding Friction- two surfaces rub against each other.  Viscous Friction- objects that move in water or other fluids, oil changes sliding friction to viscous friction.  Rolling Friction- one object rolling over another, like wheel rolling over a road.

 Newton’s Third Law  That for every action there is an equal and opposite reaction force.  The reaction force is equal in magnitude and opposite in direction  All forces come in pairs  The action/reaction forces act on separate objects not the same object

 Momentum- the mass of an object multiplied by its speed or velocity  Increase mass or speed, you increase its momentum  Units  Kg*m/sec momentum mass Velocity

 Law of Conservation of Momentum- if interaction objects are not influenced by outside forces (friction), the total amount of momentum cannot change.  The momentum gained by one body in an interaction is equal to the momentum lost by the other body.  That means momentum can also be positive (moving to the right) or negative (moving to the left).

 Momentum before collision= momentum after collision Momentum before Momentum After Mass Velocity