Motion and Motion and ForcesForces

MOTIONMOTION

S8P3. Students will investigate relationship between force, mass, and the motion of objects. a. Determine the relationship between velocity and acceleration.

How are forces and How are forces and motion related?motion related?

A force is a A force is a pushpush or a or a pullpull that can result in that can result in motion. motion. When a When a forceforce has been has been applied to an object applied to an object and the object and the object movesmoves, , workwork is being done. is being done.

How can motion be How can motion be described?described?

By using a By using a referencereference pointpoint – A (usually) – A (usually)

stationary object that stationary object that helps you detect the helps you detect the motion of an object. motion of an object. (Ex. tree, house etc.)(Ex. tree, house etc.)

Once the reference Once the reference point is determined you point is determined you

can define motion by can define motion by speedspeed, , positionposition, and , and

directiondirection..

What is speed?What is speed?

Speed refers to how Speed refers to how fastfast an object travels. (Rate at an object travels. (Rate at which an object moves.) which an object moves.)

Depends on:Depends on:

–DistanceDistance

–TimeTime

Various forms of speed: Various forms of speed:

–InstantaneousInstantaneous– speed at a – speed at a given moment (speedometer) given moment (speedometer)

–ConstantConstant– speed that doesn’t – speed that doesn’t change (cruise control)change (cruise control)

–ChangingChanging– speed that varies – speed that varies (running a mile)(running a mile)

–Average Average – speed used – speed used when objects are when objects are notnot moving at a moving at a constantconstant rate. rate.

–Formula: Formula:

Speed = Speed = distancedistance

timetime

Ex. If you ran the distance Ex. If you ran the distance of a football field (91 meters) of a football field (91 meters) in 30s, would you run the in 30s, would you run the same speed from start to same speed from start to finish?finish?

No, you find the average No, you find the average speed you ran.speed you ran.

s = d/ts = d/t

s = s = 91m91m

30s30s

3.03 m/s3.03 m/s

How can you graph speed?How can you graph speed?

Make up a scenario Make up a scenario about what's taking about what's taking

place for each line on place for each line on the graphthe graph

Two cars traveled at 50 Two cars traveled at 50 km/h on the same km/h on the same

highway. After 2 hours highway. After 2 hours the cars are 200 km away the cars are 200 km away from each other. How is from each other. How is

this possible?this possible?THEY HAVE DIFFERENT THEY HAVE DIFFERENT

VELOCITIESVELOCITIES

What is velocity?What is velocity?

Would you rather know the hurricane’s speed or

velocity?

VelocityVelocity – speed of an object – speed of an object in a particular direction. in a particular direction.

Velocity changes when Velocity changes when speedspeed or or directiondirection of an object of an object changes. changes.

Unit would look like: 5 Unit would look like: 5 m/s NWm/s NW

Can you have a constant Can you have a constant speed but a changing velocity?speed but a changing velocity?

YesYes, the Ferris wheel can , the Ferris wheel can be moving at a constant be moving at a constant speedspeed but its constantly but its constantly changing changing directiondirection!!

How is acceleration How is acceleration related to velocity?related to velocity?

AccelerationAcceleration – rate of change – rate of change of speed (velocity)of speed (velocity)

Occurs when an object Occurs when an object changes: changes:

1.1.SpeedSpeed

2.2.DirectionDirection

3.3.BothBoth

What are the types What are the types of acceleration?of acceleration?

PositivePositive Acceleration Acceleration – – speeding upspeeding up

NegativeNegative Acceleration Acceleration – slowing down– slowing down

How do you find How do you find acceleration?acceleration?

Formula:Formula: a= a= vvff –v –vii

tt

What are velocity/time What are velocity/time graphs?graphs?

Shows change in Shows change in velocity over time velocity over time ((accelerationacceleration).).

Moving at a constant velocity

Moving at a positive acceleration – velocity changing

at constant rate.

Moving at a negative acceleration – velocity changing

at constant rate.

What is centripetal What is centripetal acceleration?acceleration?

Acceleration that occurs Acceleration that occurs in a in a circularcircular motion; motion; object traveling in a circle object traveling in a circle is constantly changing is constantly changing directionsdirections; so acceleration ; so acceleration occurs continuouslyoccurs continuously

FORCESFORCES

S8P3. Students will investigate relationship between force, mass, and the motion of objects.

b. Demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia, and friction.

What is a What is a forceforce??

A force is a A force is a pushpush or or pullpull that one body that one body exerts on another. exerts on another.

Ex. Friction, Ex. Friction, gravitygravity, , kicking a football. kicking a football.

Unit: Unit: NewtonNewton (N) (N)

What is a What is a net forcenet force??

The The sumsum of the of the forces acting on forces acting on

an object.an object.

What is a What is a balanced force?balanced force?

When the forces acting on When the forces acting on the object are the object are equalequal in size in size and and oppositeopposite in direction. in direction.Net force = Net force = 00 (forces (forces cancel each other out)cancel each other out)NoNo change in motion change in motion occurs!! occurs!!

What is an What is an unbalanced forceunbalanced force??

Occurs when forces Occurs when forces acting on the object are acting on the object are unequalunequal..

Net Force is in the Net Force is in the direction of the direction of the largerlarger force. (object will force. (object will movemove in in that direction)that direction)

What is the difference between What is the difference between balanced and unbalanced balanced and unbalanced

forces?forces?

What is What is InertiaInertia??

The tendency of an The tendency of an object to object to resistresist change.change.

Which has a greater Which has a greater inertia?inertia?

ElephantElephant – inertia – inertia depends on depends on massmass!!!!

What is What is Newton’s Newton’s 11stst Law of Law of

Motion Motion state?state?

An object in An object in motionmotion will will stay in stay in motionmotion unless an unless an outside outside forceforce acts upon it. acts upon it.

An object at An object at restrest will stay will stay at at restrest unless an outside unless an outside forceforce acts upon it. acts upon it.

What is another name What is another name for the 1for the 1stst Law? Law?

The Law of The Law of InertiaInertia

What is the relationship What is the relationship between force, mass, and between force, mass, and

acceleration?acceleration?

Force and AccelerationForce and Acceleration

The greater the The greater the forceforce applied to an object applied to an object the greater the the greater the accelerationacceleration will be. will be.

Force and MassForce and Mass

Acceleration will be less Acceleration will be less on a object that is heavier.on a object that is heavier.–Ex. Softball v. BaseballEx. Softball v. Baseball

What does Newton’s 2What does Newton’s 2ndnd Law state?Law state?

An object will An object will accelerateaccelerate in the direction of the in the direction of the netnet

force.force.

F = m x a, a = F/m, F = m x a, a = F/m, m = F/am = F/a

What is the unit for What is the unit for force?force?

NewtonNewton

kg x m/s/skg x m/s/s

Types of ForcesTypes of Forces

What is a force that opposes What is a force that opposes motion between 2 moving motion between 2 moving

objects?objects?

FRICTIONFRICTION

What does the amount What does the amount of friction depend on?of friction depend on?

1.Kind of 1.Kind of surfacesurface

2. 2. ForceForce pressing pressing surfaces together.surfaces together.

What is static What is static friction?friction?

Friction between Friction between two surfaces that two surfaces that are are notnot movingmoving past one another.past one another.

What is sliding What is sliding friction?friction?

ForceForce that opposes that opposes motion of 2 objects motion of 2 objects slidingsliding past one past one another.another.

What is Rolling What is Rolling Friction?Friction?

Opposing motion Opposing motion between two objects between two objects rollingrolling past each past each other.other.

How is friction helpful?How is friction helpful?

Without friction the tires Without friction the tires could not could not pushpush against against the ground to move the the ground to move the car forward and car forward and brakesbrakes couldn’t stop the car.couldn’t stop the car.

How can you reduce How can you reduce friction?friction?

LubricantsLubricants – are used to – are used to reduce friction. reduce friction. –Ex. Motor oil, wax, greaseEx. Motor oil, wax, grease

Switching from Switching from slidingsliding to to rollingrolling friction friction–Ex. Ball bearings between Ex. Ball bearings between wheel & axleswheel & axles

S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature.

a. Recognize that every object exerts gravitational force on every other object and that the force exerted depends on how much mass the objects have and how far apart they are.

What is Gravity?What is Gravity?

A A downwarddownward force force

Any 2 Any 2 massesmasses exert an exert an attractiveattractive force on each other. force on each other.

Strength of gravitational force Strength of gravitational force depend on:depend on:

1.) 1.) MassMass

2.) 2.) DistanceDistance

What is the law of universal What is the law of universal gravitation?gravitation?

AllAll objects are attracted to objects are attracted to each by each by gravitationalgravitational force. force.–The The largerlarger the object – The the object – The greatergreater the force the force

–The The closercloser together the together the object – the object – the greatergreater the force. the force.

Is weight a force?Is weight a force?

WeightWeight is considered is considered to be a gravitational to be a gravitational forceforce that decreases that decreases as you move from as you move from Earth.Earth.

How can you find How can you find weight?weight?

F = m x aF = m x a

W = m x 9.8 m/s/sW = m x 9.8 m/s/s

What is the What is the difference between difference between mass and weight?mass and weight?

MassMass – how much matter – how much matter makes up an objectmakes up an object

–((Doesn’tDoesn’t change as you move change as you move from the Earth to the moon.)from the Earth to the moon.)

WeightWeight – considered to be a – considered to be a gravitational forcegravitational force

–((DecreasesDecreases as you move from as you move from the Earth to the moon.)the Earth to the moon.)

What is acceleration What is acceleration due to gravity?due to gravity?

Anything that falls Anything that falls through the air falls at through the air falls at an acceleration of an acceleration of 9.8m/s/s9.8m/s/s..

What is Air What is Air Resistance?Resistance?

Effects anything that is in Effects anything that is in Earth’s Earth’s atmosphereatmosphere. .

UpwardUpward force that opposes force that opposes gravitygravity of anything falling of anything falling through the air.through the air.

Air Resistance Air Resistance Depends on 3 things:Depends on 3 things:

1. 1. SPEEDSPEED

2. SIZE2. SIZE

3. 3. SHAPESHAPE

of an object.of an object.

If there were If there were no air no air resistance a resistance a hammerhammer and and featherfeather would would fall at the fall at the same time. same time.

What is a projectile?What is a projectile?

Anything that Anything that is is thrownthrown or or shotshot through the air.through the air.

Why do projectiles Why do projectiles follow a curved follow a curved

path?path?

They follow a curved They follow a curved path due to pull of path due to pull of gravitygravity..–Ex: An arrow, Ex: An arrow, Bullet, Bullet, BasketballBasketball

What is Newton’s 3What is Newton’s 3rdrd Law Law of Motion?of Motion?

When one object exerts a When one object exerts a forceforce on a second object, the on a second object, the second one exerts a force second one exerts a force that is that is equalequal and in size and and in size and oppositeopposite in direction. in direction.

““Action/Reaction OccursAction/Reaction Occurs

What is Momentum?What is Momentum?

Momentum is related to how Momentum is related to how much much forceforce is needed to is needed to change an object’s motion.change an object’s motion.

Momentum = Momentum = massmass x x velocityvelocity

p= m x vp= m x v

What is the law of What is the law of conservation of momentum?conservation of momentum?

Momentum can be Momentum can be transferredtransferred from one from one object to anotherobject to another

What is the relationship What is the relationship between mass and velocity?between mass and velocity?

If two trucks have same If two trucks have same velocity, but different velocity, but different masses then . . . masses then . . .

the truck with the the truck with the largerlarger massmass has more has more momentummomentum