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Chapter 6
Forces in Motion
Which would fall faster off a cliff, Wile E. Coyote or a boulder?
Acceleration due to Gravity: ________________________________________
Objects fall to the ground at the same rate
_______________________________________________________________
because the acceleration due to gravity is the same for all objects
Objects accelerate towards earth at a ________________
rate of acceleration
constant
9.8 m/s/s
second
equal to _____________.
For every ________________
an object is falling,
9.8 m/s
its downward velocity increases by ________________.
Why does a sheet of paper fall more slowly
than the same sheet of paper crumpled into
air resistance
a ball? _____________________________
Air (a _________)
gas
is also a ____________,
fluid
so an object falling through it would be
fluid
friction
affected by ___________
______________
opposing its motion. This is called _______
air
resistance
___________________.
A flat piece of paper
has more air resistance than a crumpled
piece of paper.
Terminal Velocity: Because the air resistance _______________
increases
as an object’s
upward
increases
speed _________________,
eventually the _______________
force of air
downward
resistance will equal the __________________
force of gravity and the
acceleration will be ___________.
The object will then fall at _______________
zero
constant
terminal
velocity
velocity, which is called _______________
_______________.
Free fall: An object is in free fall only if _________________
gravity
is the only force
vacuum
acting on it. This can only occur in a _________________
(where there is no
air resistance).
Orbiting: An object is orbiting when it is traveling in a _______________
circular
path
around another object. It is moving by the combination of ___
2 motions: it is
forward
speed
free
moving _____________
at constant ___________
and also ___________
falling
______________
because of __________________
pulling it toward the object
gravity
orbit
at the center of the ____________.
These two motions cause the path the object
travels to be _______________.
curved
The unbalanced force that causes objects to
move in a circular path is called a __________________
force, provided by
centripetal
gravity
________________.
Projectile motion: the ______________
curved
path an object follows when thrown
or propelled near the ______________
____
This is
surface
of _____
the _____________.
Earth
forward
horizontal
a combination of the ________________
(__________________)
motion which
is _________________
combined with the ________________
velocity because
constant
vertical
__________________
accelerates it ____________________.
gravity
downward
Which will fall faster from the top of a tall building, an elephant or a feather?
They will land at the same time because
Option 1: ___________________________________
acceleration due to gravity is the same
___________________________________________
for all objects.
___________________________________________
The elephant will land first because it
Option 2: ___________________________________
has a larger mass.
___________________________________________
___________________________________________
The feather will land first because it
Option 3: ___________________________________
has less air resistance.
___________________________________________
___________________________________________
Scenario 1: This happens in air. Therefore we must
consider ____________________.
This depends on
air resistance
1. __________________________________
the speed of the falling object
2. __________________________________
the surface area of the falling object
Which would have the greater surface area, the elephant or the feather?
_____________________
So which should land first? __________________
the feather?
the elephant
speed
But air resistance also depends on the _____________
at which the object falls.
The faster it falls, the greater the __________________
it encounters. An object
air resistance
accelerate
will continue to __________________
as it falls until the upward force of
____________________
equals the downward force of ________________.
air resistance
gravity
After that, the object will fall at a constant speed, called ___________
_________.
terminal velocity
air resistance
The feather reaches the speed where _______________
equals the force of
________________
much sooner (and at a slower speed) than the elephant, so
gravity
its terminal velocity is much less and it falls to earth more slowly. The elephant
mass
has a greater __________
and therefore a greater force due to gravity, and must
reach a higher speed before air resistance pushing up can balance the force
of gravity pulling down. Actually, it never reaches this point, so it never reaches
_____________________.
It continues to________________
for the entire fall.
terminal velocity
accelerate
Conclusion for falling in air: The _____________
elephant
falls faster than the
feather
terminal velocity
______________
because it never reaches a ___________
____________,
but continues to _______________
as it falls. The feather reaches terminal
accelerate
velocity very early in its fall, so the remainder of its fall will occur with a
__________
slower _____________.
velocity
Newton’s Laws of Motion
rest
rest
Newton’s First Law of Motion: An object at _________
remains at __________
motion
and an object in _____________
remains in ______________
at constant
motion
speed
straight
line
_______________
and in a ________________
____________
unless acted
on by an ___________________
force.
unbalanced
Question: If you are sitting still in your seat on a bus that is traveling 100 km/h
in motion
on a highway, is your body at rest or in motion?________________________
What force usually stops an object from remaining in motion? ______________
friction
tendency
Inertia: the _______________
of all objects to ____________
resist
any change in
mass
inertia
motion. The more _________
an object has, the more _______________
it has.
Newton’s Second Law of Motion: The ____________________
acceleration
of an object
mass
force
depends on the ___________
of the object and the amount of _____________
applied.
increases
For the same force, an object’s acceleration ________________
as its mass
decreases
decreases
_______________
and its acceleration ________________
as its mass
________________.
increases
For constant mass, an object’s acceleration ___________
increases
as the force on it _________________,
and its acceleration ______________
increases
decreases
as the force on it _________________.
decreases
Newton’s Second Law of Motion – mathematical formula:
F
a = _______
m
acceleration = _______________
Force
mass
Algebraically, this formula can be rearranged to solve for each of the 3
variables: F = ma
m= F
a
Example: If you hit an object of unknown mass with a force of 15 N, and the
3 kg
object 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 is
the 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 ___________
force
on a second object, the second object exerts an _____________
and
equal
opposite
__________________
force on the first object.
All forces act in ___________,
pairs
one force pushing one way, and another
opposite
force pushing in the ________________
direction. This happens whether there
is motion or no motion.
Examples of opposite force pairs:
red
A student sitting on a chair. The________
arrow shows the force of the student’s
body pushing on the chair, and the ______________
yellow
arrow shows the force of the chair pushing up on the
equal
student. Since the forces are __________,
there is
no motion.
When a hunter shoots a ____________
bullet
from his
gun, the gun powder explosion pushes
forward
the bullet _______________,
exerting a backwards force into the
gun
_______,
which causes the gun to
push back into the hunter’s
shoulder
_____________,
which is exerting
gun
another force on the ________.
property
Momentum: a _______________
of a moving object that depends on the
object’s _____________
and __________________.
The more momentum
mass
velocity
harder
stop
an object has, the ________________
it is to __________
it or change its
___________________.
direction
Conservation of Momentum: Any time two or more objects interact, they may
momentum
_________________
momentum, but the total amount of ________________
exchange
stays the same.
pool
Example: playing _____________.
When the cue ball hits another ball which
is stationary, the cue ball ___________
or ________________
and the other ball
stops
slows down
starts ________________.
moving
The equation for
momentum (p) is
p= mxv
.
What is the momentum of
an 80 kg basketball player
driving to the basket with a
constant velocity of 8 m/s?
p = m x v = 80 kg x 8 m/s = 640 kg.m/s
Conservation of Momentum can be explained by Newton’s __________
Third
_______.
Law
In the example of the pool balls, the cue ball hit the other ball with a certain amount
force
action
reaction
of ____________,
which was the __________
force. The _____________
force
was the ___________
but _____________
force exerted on the cue ball by the
equal
opposite
moving
pool ball. The ___________
force made the pool ball start _______________
and
action
the ________________
reaction
force made the cue ball ______________.
stop
How does Newton’s second law explain why it is easier to push a bicycle than to
push a car with the same acceleration? The bicycle has a smaller mass, so
a smaller force is required to give it the
same acceleration as the car.
What are two ways that you can increase the acceleration of a loaded grocery
cart? 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 feather
reach the ground first?
gravity
The only force acting on the objects is the force of ____________.
The
force the elephant experiences is much ___________
than the force the
greater
feather experiences, so the elephant should experience greater acceleration.
mass
But according to Newton’s First Law of Motion, the _________
of an object
acceleration
mass
resists _______________.
Therefore, the greater __________
of the
small
elephant (which tends to produce __________
acceleration) offsets the
influence of the greater _____________.
It is the __________________
force
force/mass
ratio which determines the ___________________.
acceleration
=a=g
All objects (regardless of
their mass) experience the
acceleration
same __________________
when in a state of free fall.
gravity
When the only force is _________,
the acceleration is the _________
same
value for all objects.
Chapter 6
Forces in Motion
Which would fall faster off a cliff, Wile E. Coyote or a boulder?
Acceleration due to Gravity: ________________________________________
_______________________________________________________________
Objects accelerate towards earth at a ________________ rate of acceleration
equal to _____________. For every ________________ an object is falling,
its downward velocity increases by ________________.
Why does a sheet of paper fall more slowly
than the same sheet of paper crumpled into
a 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 paper
has more air resistance than a crumpled
piece of paper.
Terminal Velocity: Because the air resistance _______________ as an object’s
speed _________________, eventually the _______________ force of air
resistance 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 force
acting on it. This can only occur in a _________________ (where there is no
air resistance).
Orbiting: An object is orbiting when it is traveling in a _______________ path
around another object. It is moving by the combination of ___ motions: it is
moving _____________ at constant ___________ and also ___________
______________ because of __________________ pulling it toward the object
at the center of the ____________. These two motions cause the path the object
travels to be _______________. The unbalanced force that causes objects to
move in a circular path is called a __________________ force, provided by
________________.
Projectile motion: the ______________ path an object follows when thrown
or propelled near the ______________ ____ _____ _____________. This is
a combination of the ________________ (__________________) motion which
is _________________ 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 object
will 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, so
its terminal velocity is much less and it falls to earth more slowly. The elephant
has a greater __________ and therefore a greater force due to gravity, and must
reach a higher speed before air resistance pushing up can balance the force
of 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 _____________
elephant
falls faster than the
feather
terminal velocity
______________
because it never reaches a ___________
____________,
but continues to _______________
as it falls. The feather reaches terminal
accelerate
velocity very early in its fall, so the remainder of its fall will occur with a
__________
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 acted
on by an ___________________ force.
Question: If you are sitting still in your seat on a bus that is traveling 100 km/h
on 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 in
motion. The more _________ an object has, the more _______________ it has.
Newton’s Second Law of Motion: The ____________________ of an object
depends 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 3
variables: F =
m=
Example: If you hit an object of unknown mass with a force of 15 N, and the
object 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 is
the 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 another
force pushing in the ________________ direction. This happens whether there
is 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 the
student. Since the forces are __________, there is
no motion.
When a hunter shoots a ____________ from his
gun, the gun powder explosion pushes
the bullet _______________,
exerting a backwards force into the
_______, which causes the gun to
push back into the hunter’s
_____________, which is exerting
another force on the ________.
Momentum: a _______________ of a moving object that depends on the
object’s _____________ and __________________. The more momentum
an 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 which
is stationary, the cue ball ___________ or ________________ and the other ball
starts ________________.
The equation for
momentum (p) is
p=
.
What is the momentum of
an 80 kg basketball player
driving to the basket with a
constant 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 amount
of ____________, which was the __________ force. The _____________ force
was the ___________ but _____________ force exerted on the cue ball by the
pool ball. The ___________ force made the pool ball start _______________ and
the ________________ force made the cue ball ______________.
How does Newton’s second law explain why it is easier to push a bicycle than to
push a car with the same acceleration?
What are two ways that you can increase the acceleration of a loaded grocery
cart?
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 feather
reach the ground first?
The only force acting on the objects is the force of ____________. The
force the elephant experiences is much ___________ than the force the
feather experiences, so the elephant should experience greater acceleration.
But according to Newton’s First Law of Motion, the _________ of an object
resists _______________. Therefore, the greater __________ of the
elephant (which tends to produce __________ acceleration) offsets the
influence of the greater _____________. It is the __________________
ratio which determines the ___________________.
=a=g
All objects (regardless of
their mass) experience the
same __________________
when in a state of free fall.
When the only force is _________,
the acceleration is the _________
value for all objects.