Chapter 6

Forces in Motion

Acceleration due to Gravity: _______________________________________________________________________________________________________Objects accelerate towards earth at a ________________ rate of accelerationequal to _____________. For every ________________ an object is falling,its downward velocity increases by ________________.

Objects fall to the ground at the same ratebecause the acceleration due to gravity is the same for all objects

Which would fall faster off a cliff, Wile E. Coyote or a boulder?

constant9.8 m/s/s second

9.8 m/s

Why does a sheet of paper fall more slowlythan the same sheet of paper crumpled intoa ball? _____________________________air resistance

Air (a _________) is also a ____________,so an object falling through it would be affected by ___________ ______________opposing its motion. This is called __________________________. A flat piece of paperhas more air resistance than a crumpledpiece of paper.

gas fluid

fluid frictionair

resistance

Terminal Velocity: Because the air resistance _______________ as an object’sspeed _________________, eventually the _______________ force of airresistance will equal the __________________ force of gravity and the acceleration will be ___________. The object will then fall at _______________velocity, which is called _______________ _______________.

increasesincreases upward

downwardzero constant

terminal velocity

Free fall: An object is in free fall only if _________________ is the only forceacting on it. This can only occur in a _________________ (where there is noair resistance).

gravityvacuum

Orbiting: An object is orbiting when it is traveling in a _______________ patharound another object. It is moving by the combination of ___ motions: it ismoving _____________ at constant ___________ and also _________________________ because of __________________ pulling it toward the objectat the center of the ____________. These two motions cause the path the objecttravels to be _______________. The unbalanced force that causes objects tomove in a circular path is called a __________________ force, provided by________________.

circular2

forward speed freefalling gravity

orbitcurved

centripetalgravity

Projectile motion: the ______________ path an object follows when thrownor propelled near the ______________ ____ _____ _____________. This is a combination of the ________________ (__________________) motion whichis _________________ combined with the ________________ velocity because__________________ accelerates it ____________________.

curvedsurface of the Earthforward horizontal

constant verticalgravity downward

Which will fall faster from the top of a tall building, an elephant or a feather?

Option 1: _________________________________________________________________________________________________________________________Option 2: _________________________________________________________________________________________________________________________Option 3: _________________________________________________________________________________________________________________________

Scenario 1: This happens in air. Therefore we must consider ____________________. This depends on

1. __________________________________2. __________________________________

They will land at the same time becauseacceleration due to gravity is the same for all objects.The elephant will land first because ithas a larger mass.

The feather will land first because ithas less air resistance.

air resistancethe speed of the falling objectthe surface area of the falling object

Which would have the greater surface area, the elephant or the feather?_____________________ So which should land first? __________________But air resistance also depends on the _____________ at which the object falls.The faster it falls, the greater the __________________ it encounters. An objectwill continue to __________________ as it falls until the upward force of____________________ equals the downward force of ________________. After that, the object will fall at a constant speed, called ___________ _________.The feather reaches the speed where _______________ equals the force of________________ much sooner (and at a slower speed) than the elephant, soits terminal velocity is much less and it falls to earth more slowly. The elephanthas a greater __________ and therefore a greater force due to gravity, and mustreach a higher speed before air resistance pushing up can balance the forceof gravity pulling down. Actually, it never reaches this point, so it never reaches_____________________. It continues to________________ for the entire fall.

the elephant the feather?speed

air resistanceaccelerate

air resistance gravityterminal velocity

air resistance

gravity

mass

terminal velocity accelerate

Conclusion for falling in air: The _____________ falls faster than the ______________ because it never reaches a ___________ ____________,but continues to _______________ as it falls. The feather reaches terminalvelocity very early in its fall, so the remainder of its fall will occur with a __________ _____________.

elephantfeather terminal velocity

accelerate

slower velocity

Newton’s Laws of Motion

Newton’s First Law of Motion: An object at _________ remains at __________and an object in _____________ remains in ______________ at constant_______________ and in a ________________ ____________ unless actedon by an ___________________ force.

rest rest

motion motionspeed straight line

unbalanced

Question: If you are sitting still in your seat on a bus that is traveling 100 km/hon a highway, is your body at rest or in motion?________________________

What force usually stops an object from remaining in motion? ______________

in motion

friction

Inertia: the _______________ of all objects to ____________ any change inmotion. The more _________ an object has, the more _______________ it has.

tendency resistmass inertia

Newton’s Second Law of Motion: The ____________________ of an objectdepends on the ___________ of the object and the amount of _____________applied. For the same force, an object’s acceleration ________________ as its mass_______________ and its acceleration ________________ as its mass________________. For constant mass, an object’s acceleration ___________as the force on it _________________, and its acceleration ______________as the force on it _________________.

accelerationmass force

increasesdecreases decreasesincreases increases

increases decreasesdecreases

Newton’s Second Law of Motion – mathematical formula:

a = _______

Fm

acceleration = _______________Forcemass

Algebraically, this formula can be rearranged to solve for each of the 3variables: F = m = ma F

a

Example: If you hit an object of unknown mass with a force of 15 N, and theobject then accelerates at 5 m/s/s, what is the mass of the object? ________3 kg

Example: Calculate the force of gravity acting on your 6 kg backpack. (This isthe weight of your backpack.) F = ma = 6 kg x 9.8 m/s/s = 58.8 N

Example: A 50 g skater pushes off from a wall with a force of 200N. What is the skater’s acceleration? a = F/m = 200 N/50 g = 4 m/s/s

Newton’s Third Law of Motion: Whenever one object exerts a ___________on a second object, the second object exerts an _____________ and __________________ force on the first object.

forceequal

opposite

All forces act in ___________, one force pushing one way, and anotherforce pushing in the ________________ direction. This happens whether thereis motion or no motion.Examples of opposite force pairs:A student sitting on a chair. The________ arrow shows the force of the student’s

body pushing on the chair, and the ______________arrow shows the force of the chair pushing up on thestudent. Since the forces are __________, there isno motion.

pairsopposite

redyellow

equal

When a hunter shoots a ____________ from hisgun, the gun powder explosion pushesthe bullet _______________, exerting a backwards force into the_______, which causes the gun to push back into the hunter’s_____________, which is exertinganother force on the ________.

bullet

forward

gun

shouldergun

Momentum: a _______________ of a moving object that depends on theobject’s _____________ and __________________. The more momentuman object has, the ________________ it is to __________ it or change its___________________.

Conservation of Momentum: Any time two or more objects interact, they may_________________ momentum, but the total amount of ________________stays the same.Example: playing _____________. When the cue ball hits another ball whichis stationary, the cue ball ___________ or ________________ and the other ball

starts ________________.

property

mass velocityharder stop

direction

exchange momentum

pool

stops slows down

The equation formomentum (p) isp = .

What is the momentum ofan 80 kg basketball playerdriving to the basket with aconstant velocity of 8 m/s?

m x v

p = m x v = 80 kg x 8 m/s = 640 kg.m/s

moving

Conservation of Momentum can be explained by Newton’s __________ _______.In the example of the pool balls, the cue ball hit the other ball with a certain amountof ____________, which was the __________ force. The _____________ forcewas the ___________ but _____________ force exerted on the cue ball by thepool ball. The ___________ force made the pool ball start _______________ andthe ________________ force made the cue ball ______________.

Third Law

force action reactionequal opposite

action movingreaction stop

How does Newton’s second law explain why it is easier to push a bicycle than topush a car with the same acceleration? The bicycle has a smaller mass, so

a smaller force is required to give it thesame acceleration as the car.

What are two ways that you can increase the acceleration of a loaded grocerycart? You can increase the force applied to the cart, or you can decrease the

mass of the cart by removing some of the objects from it.

How does Newton’s third law explain how a rocket takes off?The hot gases expelled from the back of the rocket produce a reaction force on the rocket that lifts and accelerates the rocket.

In the case of no air (or air resistance), will the elephant or the featherreach the ground first?

The only force acting on the objects is the force of ____________. Theforce the elephant experiences is much ___________ than the force thefeather experiences, so the elephant should experience greater acceleration.But according to Newton’s First Law of Motion, the _________ of an objectresists _______________. Therefore, the greater __________ of the elephant (which tends to produce __________ acceleration) offsets theinfluence of the greater _____________. It is the __________________ratio which determines the ___________________.

= a = g

gravity

greater

massacceleration mass

small

force force/massacceleration

All objects (regardless oftheir mass) experience the same __________________when in a state of free fall. When the only force is _________,the acceleration is the _________value for all objects.

acceleration

gravity

same

Chapter 6

Forces in Motion

Acceleration due to Gravity: _______________________________________________________________________________________________________Objects accelerate towards earth at a ________________ rate of accelerationequal to _____________. For every ________________ an object is falling,its downward velocity increases by ________________.

Which would fall faster off a cliff, Wile E. Coyote or a boulder?

Why does a sheet of paper fall more slowlythan the same sheet of paper crumpled intoa ball? _____________________________

Air (a _________) is also a ____________,so an object falling through it would be affected by ___________ ______________opposing its motion. This is called __________________________. A flat piece of paperhas more air resistance than a crumpledpiece of paper.

Terminal Velocity: Because the air resistance _______________ as an object’sspeed _________________, eventually the _______________ force of airresistance will equal the __________________ force of gravity and the acceleration will be ___________. The object will then fall at _______________velocity, which is called _______________ _______________.

Free fall: An object is in free fall only if _________________ is the only forceacting on it. This can only occur in a _________________ (where there is noair resistance).

Orbiting: An object is orbiting when it is traveling in a _______________ patharound another object. It is moving by the combination of ___ motions: it ismoving _____________ at constant ___________ and also _________________________ because of __________________ pulling it toward the objectat the center of the ____________. These two motions cause the path the objecttravels to be _______________. The unbalanced force that causes objects tomove in a circular path is called a __________________ force, provided by________________.

Projectile motion: the ______________ path an object follows when thrownor propelled near the ______________ ____ _____ _____________. This is a combination of the ________________ (__________________) motion whichis _________________ combined with the ________________ velocity because__________________ accelerates it ____________________.

Which will fall faster from the top of a tall building, an elephant or a feather?

Option 1: _________________________________________________________________________________________________________________________Option 2: _________________________________________________________________________________________________________________________Option 3: _________________________________________________________________________________________________________________________

Scenario 1: This happens in air. Therefore we must consider ____________________. This depends on

1. __________________________________2. __________________________________

Which would have the greater surface area, the elephant or the feather?_____________________ So which should land first? __________________But air resistance also depends on the _____________ at which the object falls.The faster it falls, the greater the __________________ it encounters. An objectwill continue to __________________ as it falls until the upward force of____________________ equals the downward force of ________________. After that, the object will fall at a constant speed, called ___________ _________.The feather reaches the speed where _______________ equals the force of________________ much sooner (and at a slower speed) than the elephant, soits terminal velocity is much less and it falls to earth more slowly. The elephanthas a greater __________ and therefore a greater force due to gravity, and mustreach a higher speed before air resistance pushing up can balance the forceof gravity pulling down. Actually, it never reaches this point, so it never reaches_____________________. It continues to________________ for the entire fall.

Conclusion for falling in air: The _____________ falls faster than the ______________ because it never reaches a ___________ ____________,but continues to _______________ as it falls. The feather reaches terminalvelocity very early in its fall, so the remainder of its fall will occur with a __________ _____________.

elephantfeather terminal velocity

accelerate

slower velocity

Newton’s Laws of Motion

Newton’s First Law of Motion: An object at _________ remains at __________and an object in _____________ remains in ______________ at constant_______________ and in a ________________ ____________ unless actedon by an ___________________ force.

Question: If you are sitting still in your seat on a bus that is traveling 100 km/hon a highway, is your body at rest or in motion?________________________

What force usually stops an object from remaining in motion? ______________

Inertia: the _______________ of all objects to ____________ any change inmotion. The more _________ an object has, the more _______________ it has.

Newton’s Second Law of Motion: The ____________________ of an objectdepends on the ___________ of the object and the amount of _____________applied. For the same force, an object’s acceleration ________________ as its mass_______________ and its acceleration ________________ as its mass________________. For constant mass, an object’s acceleration ___________as the force on it _________________, and its acceleration ______________as the force on it _________________.

Newton’s Second Law of Motion – mathematical formula:

a = _______

acceleration = _______________

Algebraically, this formula can be rearranged to solve for each of the 3variables: F = m =

Example: If you hit an object of unknown mass with a force of 15 N, and theobject then accelerates at 5 m/s/s, what is the mass of the object? ________

Example: Calculate the force of gravity acting on your 6 kg backpack. (This isthe weight of your backpack.)

Example: A 50 g skater pushes off from a wall with a force of 200N. What is the skater’s acceleration?

Newton’s Third Law of Motion: Whenever one object exerts a ___________on a second object, the second object exerts an _____________ and __________________ force on the first object.

All forces act in ___________, one force pushing one way, and anotherforce pushing in the ________________ direction. This happens whether thereis motion or no motion.Examples of opposite force pairs:A student sitting on a chair. The________ arrow shows the force of the student’s

body pushing on the chair, and the ______________arrow shows the force of the chair pushing up on thestudent. Since the forces are __________, there isno motion.

When a hunter shoots a ____________ from hisgun, the gun powder explosion pushesthe bullet _______________, exerting a backwards force into the_______, which causes the gun to push back into the hunter’s_____________, which is exertinganother force on the ________.

Momentum: a _______________ of a moving object that depends on theobject’s _____________ and __________________. The more momentuman object has, the ________________ it is to __________ it or change its___________________.

Conservation of Momentum: Any time two or more objects interact, they may_________________ momentum, but the total amount of ________________stays the same.Example: playing _____________. When the cue ball hits another ball whichis stationary, the cue ball ___________ or ________________ and the other ball

starts ________________.

The equation formomentum (p) isp = .

What is the momentum ofan 80 kg basketball playerdriving to the basket with aconstant velocity of 8 m/s?

Conservation of Momentum can be explained by Newton’s __________ _______.In the example of the pool balls, the cue ball hit the other ball with a certain amountof ____________, which was the __________ force. The _____________ forcewas the ___________ but _____________ force exerted on the cue ball by thepool ball. The ___________ force made the pool ball start _______________ andthe ________________ force made the cue ball ______________.

How does Newton’s second law explain why it is easier to push a bicycle than topush a car with the same acceleration?

What are two ways that you can increase the acceleration of a loaded grocerycart?

How does Newton’s third law explain how a rocket takes off?

In the case of no air (or air resistance), will the elephant or the featherreach the ground first?

The only force acting on the objects is the force of ____________. Theforce the elephant experiences is much ___________ than the force thefeather experiences, so the elephant should experience greater acceleration.But according to Newton’s First Law of Motion, the _________ of an objectresists _______________. Therefore, the greater __________ of the elephant (which tends to produce __________ acceleration) offsets theinfluence of the greater _____________. It is the __________________ratio which determines the ___________________.

= a = g

All objects (regardless oftheir mass) experience the same __________________when in a state of free fall. When the only force is _________,the acceleration is the _________value for all objects.