PHYSICSPHYSICS20142014

Sir Isaac NewtonSir Isaac Newton

Proposed 3 laws of motion in the 1600’sProposed 3 laws of motion in the 1600’s Laws explain the relationship among forces, Laws explain the relationship among forces,

matter, and motionmatter, and motion

Lesson 1Lesson 1

MotionMotion

MotionMotion

An object is in motion if the object changes An object is in motion if the object changes position relative to a reference point.position relative to a reference point.

Once an object’s reference point is known, you Once an object’s reference point is known, you can calculate:can calculate:

SpeedSpeed VelocityVelocity AccelerationAcceleration

Speed – the distance an object travels divided Speed – the distance an object travels divided by the time it takes to travel that distanceby the time it takes to travel that distance

SPEED= SPEED= distance/timedistance/time

Velocity Velocity – the speed of an object with – the speed of an object with the direction the object is moving inthe direction the object is moving in

Calculate the same as speed.Calculate the same as speed.

Measurement units are the same but Measurement units are the same but the direction is added.the direction is added.

AccelerationAcceleration – rate at which the – rate at which the velocity of an object changesvelocity of an object changes

Acceleration includes:Acceleration includes: Speeding upSpeeding up Slowing downSlowing down Changing directionChanging direction

GRAVITYGRAVITY

The force of The force of attraction between all attraction between all masses in the masses in the universe; especially universe; especially the attraction of the the attraction of the earth's mass for earth's mass for bodies near its bodies near its surface .surface .

ForcesForces

Force: Force: a push or pull on an objecta push or pull on an object

When an object is speeding up, slowing When an object is speeding up, slowing down or changing direction, a force is down or changing direction, a force is acting upon the objectacting upon the object

Types of ForcesTypes of Forces

1. 1. Balanced ForcesBalanced Forces

*do not change an object’s motion*do not change an object’s motion

*all forces acting on the object are *all forces acting on the object are equalequal

Types of ForcesTypes of Forces

2. 2. Unbalanced ForcesUnbalanced Forces

*can cause an object to start *can cause an object to start moving, stop moving, or change moving, stop moving, or change directiondirection

*one force is greater than another *one force is greater than another force acting upon the objectforce acting upon the object

Lesson 2Lesson 2

Newton’s Laws of MotionNewton’s Laws of Motion

InertiaInertia

The First Law is the law of inertiaThe First Law is the law of inertia

Inertia is an objects tendency to resist a change Inertia is an objects tendency to resist a change in motionin motion

First Law of MotionFirst Law of Motion

An object at rest will stay at rest An object at rest will stay at rest

ANDANDAn object in motion will stay in motion An object in motion will stay in motion

UNLESS UNLESS

acted upon by an unbalanced force.acted upon by an unbalanced force.

Examples of forces: push or pull, friction, air Examples of forces: push or pull, friction, air resistanceresistance

FrictionFriction Slows an object until it stopsSlows an object until it stops Produces heatProduces heat Wears the object downWears the object down

Second Law of MotionSecond Law of Motion

The force of an object is equal to its mass times The force of an object is equal to its mass times its accelerationits acceleration..

F = M x AF = M x A

(force) (mass) (acceleration)(force) (mass) (acceleration)

                                    

                                                                        

                                                                                

•The greater the FORCE the greater the The greater the FORCE the greater the acceleration. acceleration.

•The larger the MASS of an object the greater The larger the MASS of an object the greater the force required to accelerate or slow down the force required to accelerate or slow down the objectthe object

It’s easier to move a soccer ball than it is to It’s easier to move a soccer ball than it is to move a brick wallmove a brick wall

Third Law of MotionThird Law of Motion

For every action there is an For every action there is an equal and opposite reaction.equal and opposite reaction.

Consider the flying motion of birds. A bird flies Consider the flying motion of birds. A bird flies by use of its wings. The wings of a bird by use of its wings. The wings of a bird push push air downwardsair downwards. Since forces result from . Since forces result from mutual interactions, the air must also be mutual interactions, the air must also be pushing the bird upwardspushing the bird upwards

the direction of the force on the air the direction of the force on the air (downwards) is opposite the direction of the (downwards) is opposite the direction of the force on the bird (upwards).. force on the bird (upwards)..

A person paddling a boatA person paddling a boat

pushes backward, causing pushes backward, causing

the canoe to move forwardthe canoe to move forward

What enables us to walk? To move forward What enables us to walk? To move forward parallel to the floor we must parallel to the floor we must push backward on push backward on the floorthe floor with one foot. By the third law, the with one foot. By the third law, the floor pushes forwardfloor pushes forward, moving us forward. Then , moving us forward. Then the process is repeated with the other foot, etc. the process is repeated with the other foot, etc. This This cannot occur unless there is friction cannot occur unless there is friction between the foot and floorbetween the foot and floor and on a frictionless and on a frictionless surface we would not be able to walk. surface we would not be able to walk.

Consider the motion of a car on the way to school. Consider the motion of a car on the way to school. A car is equipped with wheels which spin A car is equipped with wheels which spin backwards. backwards.

As the As the wheels spin backwardswheels spin backwards, they grip the road , they grip the road and and push the road backwardspush the road backwards. The road must also . The road must also be be pushing the wheels forwardpushing the wheels forward..

For every action, there is an equal (in size) and For every action, there is an equal (in size) and opposite (in direction) reaction. Action-reaction opposite (in direction) reaction. Action-reaction force pairs make it possible for cars to move along force pairs make it possible for cars to move along a roadway surface. a roadway surface.

Lesson 3Lesson 3

Work and EnergyWork and Energy

WorkWork

WorkWork – the exertion of a force that causes an – the exertion of a force that causes an object to moveobject to move

W = F x DW = F x D

(work) (force) (distance)(work) (force) (distance)

EnergyEnergy

EnergyEnergy – the ability to do work– the ability to do work

Work can be thought of as a transfer of energy.Work can be thought of as a transfer of energy.

Two types of energy:Two types of energy:

1. 1. PotentialPotential

2. 2. KineticKinetic

Types of EnergyTypes of Energy

Potential EnergyPotential Energy Energy that is stored Energy that is stored Has the potential to do workHas the potential to do work

Kinetic EnergyKinetic Energy Energy in motion (of moving objects)Energy in motion (of moving objects) In process of doing the workIn process of doing the work

Light, Sound and Heat Energy move Light, Sound and Heat Energy move in Wavesin Waves