Newton’s First Law

Newton’s Second law

Newton’s Third law

Force is a push or pull Force can be exerted in different ways

A magnet can exert a force on a paper clip, gravity pulls that paper clip to center of earth, and there is a force that acts on the paper clip when you pick it up

All forces acting on an object is called the net force

Net force acting on a book might be gravity pulling it toward center of earth and the book pushing up on book. It doesn’t move therefore it is balanced

If two forces are in the same direction, they are added together to form the net force

If two forces are acting in opposite direction, the net for is the difference between the two forces and is in the direction of the larger force

When two forces are exerted on an object, and the net force is zero their effects cancel each other out and they do not change velocity it is a balanced force

Unbalanced forces are a result when forces on an object are not zero and the effects don’t cancel each other and their velocity changes

Page 551 figure 2

Sir Issac Newton (1642-1727) developed laws of motion

First law describes how an object moves when the net force acting on it is zero

First law states that an object at rest will remain at rest, or an object in motion will continue in motion unless an outside force acts on it. This occurs when a balanced force is applied

Inertia is an example of Newtons First Law

Friction is a force that brings all objects to rest

Before Newton people didn’t know about friction or the force that acts in opposite direction of movement

When he realized objects in motion are slowed down by an unbalanced force his first law began to make sense

An object in motion will continue forever unless an unbalanced force acts on it(like friction) or it will remain at rest unless an outside force acts on it

Static Friction: resistance of objects to begin to move… must overcome static friction to move a book across a table

Sliding friction: resistance of objects once an object is moving. Moves in opposite direction of motion

Rolling friction: less force in opposite direction than sliding friction

Force: a push or pull on an object Acceleration occurs any time there is a

change of velocity or direction of an object Newton’s Second law deals with the

acceleration of an object that will equal the net force divided by the mass and is in the direction of the net force

A=Fnet F= ma m Unit of force is in Newtons kg*m/s2

Gravity is the attraction between any two objects

It is dependent on the size of the objects and the distance between them

Weight: is the size of the gravitational force exerted on an object It can change as you move farther

from center of the earthW= m (9.8 M/S2) Where 9.8 m/sec2 is

the acceleration rate on earth

Weight and mass are different Weight is a force and is measured in

newtons It is a record of the pull of earth’s

gravity and can change depending on distance to center of earth

Mass is the amount of matter in an object and doesn’t depend on location

Speeding up: when an unbalanced force is moving in the same direction as an object …it will speed up

Slowing down: if the unbalanced force is in the opposite direction as objects velocity it will slow down

Can calculate acceleration a=fnet/m Page 559

Curved path is a result of forces that are neither in same or opposite direction acting on an object

Circular motion: movement in a circle like a merry-go-round

Your direction of motion is constantly changing which also means you are constantly acceleratingIn order to cause an object to move in circular motion at constant speed, the net force must be at right angles to the velocityCentripetal force is the net force on an object moving in a circle and is toward center of path

Satellites circle the earth and are kept in motion because of the speed they travel in orbit

They must travel at least 8 km/sec or 29,000 km/h other wise it will fall back

to earth

When an objects moves, there is air resistance

The greater the velocity, the greater the air resistance

Terminal velocity is a result of balancing the gravitational pull and air resistance and the object’s velocity remain the same

Center of mass is the point in an object that moves as if all the object’s mass were concentrated at that point

The center of mass on an oblong shape is the point if followed in a straight line (Figure 12)

3rd law states that for every action there is an equal and opposite reaction

Forces exerted by two objects on each other are often called an action-reaction force

They can be action forces or reaction forces because normally they aren’t equal

Only time they are equal is if forces act on the same object

Bird flying utilizes 3rd law

Depending on mass of objects you may not know that there is an equal but opposite reaction ie: jumping off diving board

Rocket launches uses 3rd law to push rocket upward with gases burning in opposite direction

Weightlessness is the condition that occurs in free fall when the weight of an object seems to be zero

A falling object is in free fall when the only force acting on the object is gravity and for that split second weightlessness occurs

In orbit all objects are in free fall and falling in a curved path

http://www.google.com/url?sa=t&source=web&cd=5&ved=0CCMQtwIwBA&url=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Do-265xTz2zA&ei=h4FgTOzzIY3EsAOm8uipCw&usg=AFQjCNEcUQiApBhlvScU0rRkcjwxlGrdWg