revisedforce friction physical science

8/10/2019 RevisedForce Friction Physical Science

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Do Now: What do you think when you hear the word

force- in science terms?

Objective: Compare the motion of an object acted on

by a balanced force and one acted on by anunbalanced force.


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Force andFriction


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A force is simply a push

or a pull.All forces have both size

and direction.


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Measured in Newtons (n)by a spring scale

4.4 N= 1lbs

BrainPop: Force video clip
http://www.brainpop.com/science/motionsforcesandtime/force/http://www.brainpop.com/science/motionsforcesandtime/force/http://www.brainpop.com/science/motionsforcesandtime/force/


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NET FORCES

When two or more

forces are

combined!


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1. Forces in the same direction-add

the two forces together.

+ =

1. Forces in different directions-subtract the two and figure out

which direction was the stronger of

the two.

- =


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Forces in combination

1. same direction (balanced) 50N50N= 100N

2. opposite direction (unbalanced) 100N25N=75N


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Balanced vs. unbalanced forces

Unbalanced: when the netforce on an object is not zero.

These produce a change inmotion.

Balanced: when the net force

on an object equals zero.

These do NOTproduce

change in motion.


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Balanced Force

Equal forces in oppositedirections produce no motion


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Unbalanced Forces

Unequal opposing forces

produce an unbalanced force

causing motion


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Do Now: John and Sarah are pushing on opposite ends

of a table, John 100N is pushing on the left side of the

table and Sarah is 65N. What will the net force of

opposite forces be?

SWBAT- Identify the factors that determine the friction

force between two surfaces


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Source of Friction Friction occurs

because the

surfaces of any

object is rough.

Even surfaces

that appear

smooth cause

friction.


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Rougher Surfaces

The rougher thesurface, the greaterthe friction.

Ex. Pavement ismuch rougher thangrass, more frictionis produced whenyou slide on the

pavement than ongrass.


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Mass and Friction

Objects with more

mass need more

force to overcome

friction, objects

with less mass

need less force to

overcome friction.


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Rolling Friction

RollingFriction-

Important when it

comes to means of

transportation.

Anything with

wheels using

rolling friction.


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Fluid Friction

Fluid Frictionincludes liquids andgases.

For example thefriction between airand a fast movingcar is the largest

force opposing themotion of the car.


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Static Friction

Static Friction is when

a force is applied to

the object but the

object does not move.

Static friction

disappears as soon

as the object moves.


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Do Now: Two kids sledding down a snow covered hill is

an example of what type of Friction?

Sliding friction

SWBAT- Demonstrate there understanding of the Laws

of motion


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Newtons Laws of Motion

BrainPop: Newtons Laws of Motion

video clip

1

2

3
http://www.brainpop.com/science/motionsforcesandtime/newtonslawsofmotion/http://www.brainpop.com/science/motionsforcesandtime/newtonslawsofmotion/http://www.brainpop.com/science/motionsforcesandtime/newtonslawsofmotion/http://www.brainpop.com/science/motionsforcesandtime/newtonslawsofmotion/http://www.brainpop.com/science/motionsforcesandtime/newtonslawsofmotion/http://www.brainpop.com/science/motionsforcesandtime/newtonslawsofmotion/


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Newtons First Law

(law of inertia)

An object at rest tends to stay at rest

and an object in motion tends to stayin motion unless acted upon by an

unbalanced force.

1


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Balanced Force

Equal forces in oppositedirections produce no motion


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There are fourmain types of friction: Sliding friction: ex. ice skating

Rolling friction: ex. bowling

Fluid friction (air or liquid): ex. air orwater resistance

Static friction: ex. initial friction when

moving an object

What is this unbalanced force that acts

on an object in motion?


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This will help up remember:Newtons First Law videoclip
http://www.teachertube.com/viewVideo.php?video_id=21642http://www.teachertube.com/viewVideo.php?video_id=21642http://www.teachertube.com/viewVideo.php?video_id=21642http://www.teachertube.com/viewVideo.php?video_id=21642


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Newtons Second Law

Force = Mass x Acceleration Force is measured in Newtons

ACCELERATION of GRAVITY Earth) = 9.8

m/s2

WEIGHT is a measure of the force of gravity

on the mass of an object

Weight (force) = mass x gravity (Earth)

BrainPop: Gravity video clip
http://www.brainpop.com/science/motionsforcesandtime/gravity/http://www.brainpop.com/science/motionsforcesandtime/gravity/http://www.brainpop.com/science/motionsforcesandtime/gravity/


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This will help up remember:

Newtons Second Law videoclip
http://www.teachertube.com/viewVideo.php?video_id=21643http://www.teachertube.com/viewVideo.php?video_id=21643http://www.teachertube.com/viewVideo.php?video_id=21643http://www.teachertube.com/viewVideo.php?video_id=21643


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Newtons Third Law

For every action there is an equal andopposite reaction.

3


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Newtons 3rdLaw

For every actionthere is an equal andopposite reaction.

ook to

earth

Table to

book


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Think about it . . .

What happens if you are standing on a skateboard or

a slippery floor and push against a wall? You slide in

the opposite direction (away from the wall), because

you pushed on the wall but the wall pushed back on

you with equal and opposite force.

Why does it hurt so much when you stub your toe?

When your toe exerts a force on a rock, the rock

exerts an equal force back on your toe. Theharder you hit your toe against it, the more force

the rock exerts back on your toe (and the more

your toe hurts).


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Action: earth pulls on you

Reaction: you pull on earth

Action and Reaction on Different Masses

Consider you and the earth


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Action: rocket pushes on gases

Reaction: gases push on rocket


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This will help up remember:

Newtons Third Law video clip
http://www.teachertube.com/viewVideo.php?video_id=21646http://www.teachertube.com/viewVideo.php?video_id=21646


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Now its time to create your own

You will each be assigned a specific topic within Force

and Motion.

You with be responsible for creating a 2-3 minute review

video for your topic. Each of you are about to receivethe rubric for how your video will be graded.

Using the information you have just reviewed, develop a

plan for how you want to present your material.

You will have the rest of the class period to work on this

project.

revisedforce friction physical science

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