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I. _________ m is the ______________________ that
an object contains. It is a ______________ .
A. units of mass: SI:
_________________
 are _____________________ units
 have the ____________________________
Other mass units:
1/ _____________
This is the approximate mass of a small
_________________ or of a ___________________
Conversions:
1 kg = ________ g = _________ g
1 g = _________ kg
Note:
In:
m = 10 g  g stands for _________________
In
g = 9.8 m/s2  g = ___________________
___________________
2/ The _______________ mass unit u is defined as:
(1/12) the mass of a ____________________
Conversion: 1 u = _______________ (see PhysRT)
1 proton or neutron mass = __________
3/ British: __________ (don’t need to know) ≈15 kg
II. __________w is the ____________________ (Fg)
(usually due to a planet) acting on an object.
It is a _____________ b/c is has _____________
____________________________________________
A. Units of weight are the same as for __________:
SI:
_________________  derived
British:
_________________
B. The weight of an object depends on:
1/ the ____________ of the object itself;
2/ the ___________ from the center of the planet;
3/ the ___________ of the planet.
w
more mass 
________________
or
Fg
mass of object
For the same object at 3 different _____________ :
_______ m
mass m
planet
w
_______ m
denser
planet
Mass m is___________________________.
It is a ____________________ of an object.
w is different in different locations because
_________________________________________
Remember: _____________ = __________________
C. Its magnitude can be found from:
Fg =
PhysRT:
or:
where m is the mass of the object _________
and g is the _____________________________ .
On Earth’s surface, g = _________________
Farther from the surface or on other planets,
_____________________________________________ .
Ex: Find the weight of a 45-kg goblin.
What is the force of gravity acting on the goblin?
Ex: The weight of a stick of butter is about 1.0 N.
What is its mass?
Ex: What is the weight of a 600-N student?
I. A force, F, is a ____________________________ .
A. Forces are ______________ .
•magnitude – how ___________________
•direction –_________ shows dir. of push/pull
Ex 1: F =
Ex 2: w =
Sketch:
SI force units__________________ (derived)
1N=
1 N ≈ weight of 1______________________
Ex. John pushes Jane with a 25 N force to the
right. Joan pulls Jane with a 25 N force to the
right. Draw and label both forces using a scale
of 1 cm = 5 N.
Jane
John
Joan
These two forces are drawn ____________________
b/c they have the same __________ & ___________ .
John and Joan are said to __________ a force on
or ____________ a force to Jane. We say the forces
____________ Jane. Sometimes, forces are called
____________ .
B. ____________________________ forces:
• most _____________ forces known
• can push or pull ______________physical contact.
• aka “___________________” or “ __________ ” forces
Ex. Even though ___________ is separated from
__________________ by a ____________ (nothing),
both objects are able to _____________________
on each other.
E
m
The 4 __________________ forces are listed below
from strongest to weakest:
1._________ (nuclear) –force that binds __________
and ____________ within the ______________
2._____________________ (e&m)- the force that acts
between _____________ charges; the source of
______________ ; responsible for chemical ________
between _________ or between __________________
3. _________ (nuclear)– causes nuclear __________
4.__________ – (Fg) a force between ____________
holds planets, solar systems, and galaxies
together, but is the __________________________
aka the _____________ (w)
of an object when it is on
or near a_____________ .
C. ________________ forces between 2 objects:
•result from___________________________
•occur when there is _________________
1.___________________, T:
• the _______ of wires, ropes, strings, cables, etc
• _____________ is the direction of the wire, etc
• ______________ of wire, rope, etc, not important
• results from ________________________ between
atoms and molecules __________ the wire itself.
Ex:
ceiling
wire
weight
The ___________ is the force
exerted by the wire as it
_______________on the weight.
2. ______________, Ff :
• usually ____________ motion (or ____________
motion)
• direction - usually _____________ of velocity
• acts _____________________ between 2 objects
• sliding friction: results as electron ________
between the molecules along the surface
__________________________ .
Ex: block sliding
along floor to the
right.
The surface _______________
to the ________ on the block.
v
block
Ex: block being pulled
up an incline (ramp)
Ex: block at rest
on an incline
v
v=0
____________ friction, the block would slide down.
This would be its "_______________ " motion.
Friction ____________ that motion from happening,
so friction must be directed ____________________ .
3. The ________________ force, FN :
• occurs when 2 ________________ are in contact
• direction is _________________ ( ) to both
surfaces
• results when electron bonds _____________ as
surfaces _______________________ each other
Ex: standing
on floor
The floor _________
on _______________.
Ex: block
at rest
on an
incline
The incline _________
on _______________.
D. Usually __________________ force acts on an
object at a time. ________________ diagrams make
it easier to solve these problems.
Rules for drawing free-body diagrams:
1. Imagine a _____________ surrounding the object.
2. List all:
a/ "______________" forces that cut through it
b/ "_________________" forces that cut through it
3. Draw a _______________ to represent the object.
4. Draw each force in step 2 as an ___________
whose tail begins at that _____________ .
5. Only draw _____ . Do NOT draw _____________ !
Ex: A student holds herself on a hillside
by pulling on a rope.
Drawing or sketch of
object with many forces
acting on it:
hill
Free body diagram
(FBD) of same object:
Draw a FBD of the forces acting on the
blocks in each case below.
Ex 1: block in free fall
(no air resistance)
Ex 2: block on table
at rest
Ex 3: block hanging
from a wire:
ceiling
Ex 4: block pulled
to left on frictionless
table by a pull P
P
Ex 5: block on table
sliding to the left, no
pull, but with friction
v
Notice: v is _______________ !
Ex 6: block on floor
being pulled to left by
a rope but not moving
E. Forces can be added like any other vectors:
Add:
head
to tail:
F1
and:
F2
parallelogram:
F2
F1
Magnitude of resultant force: F =
Direction of resultant force: q =
F2
F1
Ex: The resultant of two forces, 3 N
and
4N
as a function of q between them:
q (0)
Resultant
Magnitude of
resultant F:
Biggest possible magnitude  __________ the magnitudes
Smallest possible magnitude  __________ the magnitudes
As q increases, the magnitude ________________ .
F. Forces can be _______________ (broken down
into _____________________ )like any other vectors:
F
q
PhysRT:
(Mechanics
section)
Fy =
Fx =
Ex: Find the x and y components of the F below:
120 N
300
Fy =
Fx =
Newton’s 1st Law of Motion:
If the ____________________ force, Fnet, acting
on an object equals ________, then that object has
____________________ . Its acceleration a = _____ .
It is said to be in __________________ .
Because forces are ______________ and have
____________ , the x and y _______________ of the
forces often must be added up _______________
when there are forces along different _________.
Fnet = 0 really means:
________ = 0
________ = 0
Ex: A 20-N box on a table
at rest
Free body diagrams:
20-N
"At rest"  __________
Ex: A 20-N box at rest on a table being pushed
down with a 5 N force.
5-N
20-N
"At rest"  _______________
Both of these boxes are in ___________________ .
Ex: Same box sliding to the right on a horizontal
frictionless table at a constant velocity 2.0 m/s
v = 2.0 m/s
20-N
"constant velocity"  __________
Draw only the __________ , not the ____________
Notice:
1/ The free body diagram is the _________ as the
first example. Both are in ___________________ .
2/ No force is ___________ to keep box moving.
The box will continue its motion ________________.
Ex: The forces acting on
a 20-N box are shown
at right:
This box is in ___________________. It is either:
1/ _____________ (constant velocity = _____);
2/ or _____________ at a constant velocity.
Unless other information is given, it is
_______________ to tell if it is at rest or moving.
Ex. The three forces below are the only ones
acting on an 2.0-kg object. What is the
acceleration of the object?
Add up the forces:
3.0
N
4.0 N
5.0 N
The net force Fnet = _____ so a must = ____ .
This object could be _______________ or
moving with ____________________________ .
Restatement of 1st Law:
If an object is ____________ or moving with
_____________________, it is_________________.
Then the net force (Fnet ) acting on it _________ .
Ex: A B-2 bomber flying
at constant velocity:
weight ≈ 1.3 x 106 N
thrust ≈ 75 x 103 N/engine
x 4 engines
Ex. The two forces shown below act on an
object. What third force is needed to produce
equilibrium?
F1
F2
First way to solve:
• Find resultant force F
• The answer is -F:
-F ___________________ the other two forces.
Second way to solve:
1. Add the two forces using head to tail method.
2. Add a force to "bring the total force to zero."
F1
head to tail:
original
F1
F2
F2
Notice:
• Both ways give ________________________
• -F is NOT the ________________ of the other
vectors. It is the force that ________________
the other vectors, making Fnet =________. It is
sometimes called the ________________ because it
is what is needed to produce ___________________ .
Ex. Draw the vector that represents the force
that the beam exerts on point A.
building
T
A
beam
weight
A
w
The beam force is the ________________ . It must
be added to the other forces so that ___________
Ex. Increasing angle between 2 wires supporting a picture:
Case 1: vertical
wires
1
2
1
2
T = ____
in each
wire
10 N
w = 10 N
Case 2: greater
angle
2
1
2
1
10 N
T = ____
in each
wire
w = 10 N
Case 3: even
greater
angle
1
10 N
2
1
2
w = 10 N
As q increases, the tension _______________ .
T = ____
in each
wire
Ex. What has more inertia,
a truck or a baseball?
more __________
more___________
inertia
A net force is ________________ to maintain
motion. An object will maintain its motion in
the ________________ of a net force. This idea
was discovered by _____________. An object in
motion tends to ____________________ , and an
object at rest tends to _________________ . The
_______________________ that “makes” this
true is called its ___________ .
mass
Inertia is the tendency of an object to
_________________________ . More inertia (mass)
means it is __________________ for an object to…
1/ …_____________________ when it is at rest;
2/ … __________ when it is already moving; and,
3/ … ____________________ from a straight path.
In other words, ______________ is why an object
needs __________________
to maintain its motion.
This is why Newton's
Law
of
_____________ is called
Inertia
the ________________ .
a
F
net
Newton’s _____ Law:
If a net force Fnet acts on an object of mass m,
the object’s acceleration a will be:
a=
Net forces ___________________
mass ________________________
a
a
Fnet
Compare: a = Δv/t
m
is a _________________ of a
a = Fnet/m tells the _____________ of a
1/ Units:
a =
Fnet
m
=
units:
=
=
1 N = the _____________ that produces an acceleration
of __________ when applied to a mass of _________
1 kg
1N
frictionless surface
2/ a is a vector: a = 5.0 m/s2, east
a/ The magnitude of a is also called
the________________________.
Ex. Names of vectors and their magnitudes.
vector
displacement
velocity
acceleration
magnitude
b/ The direction of a is ________________ the
direction of Fnet.
Ex: In free fall, the weight w equals ________
What is the acceleration at
all five points shown?
magn.: a = __ = ___________
dir.: __________ because it is
the same direction as ______.
The acceleration is ____ 0
at the top because Fnet ____ 0
there (and everywhere else).
3/ Compare:
Newton’s 1st Law:
Newton’s 2nd Law:
FN = 20N
FN = 20N
Ff =
10 N
pull
= 10N
w = 20 N
Fnet = __________
Ff = 2 N
pull
= 10N
w = 20 N
Fnet = __________
a = ___  ___________ v
a = __________
or v = ______
F's are _______________
F's are _____________
____________________
__________________
The First Law is really just a _____________________ of
the Second Law that is true when ____________________ .
Ex: A force of 16 N pushes horizontally on a
2.0 kg mass on a frictionless surface. Draw all the
forces acting on the mass. Then find Fnet and a.
2.0
kg
Fnet =
______________
w = mg = _________________
≈ _____________ = _____
or ___________
a =
Fnet
m
=
=
=
Ex: Add a friction force of 4.0 N to the previous
example. Again, draw all forces acting on the
mass, find Fnet and find a.
2.0
kg
Now, Fnet =
____________
a =
Fnet
m
a is _________ now b/c Fnet is___________ .
Which way is the mass in the previous problem moving?
___________. Why? Because Fnet is to the right, a is _____
_______. But a only tells the direction of _______, not ____ .
Case 1:
positive v
Fnet
vi
2.0
kg
2.0
kg
vf ___ vi so Dv = vf - vi ___ 0 and so a = Dv/t __ 0
Case 2:
negative v
vi
2.0
kg
Fnet
2.0
kg
vf ___ vi so Dv = vf - vi ___ 0 and so a = Dv/t __ 0
In both cases, Fnet is ________, so Dv and a are ________
but, in Case 2, v is ________________ .
Ex: A 2.0 kg box slides to the right over a surface
with a constant frictional force of 2 N. Draw all
forces acting on the mass, find Fnet and a.
v
2.0
kg
Fnet = __________
= ________
a =
Fnet
m
The box is _________________ , because Fnet
and v are in ______________________________ .
Ex: Why do all objects fall with same acceleration
in free fall (no air resistance)?
small mass
Newton's
2nd Law :
big mass:
a=
a=
=
=
a=
=
=
Which object gets pulled down with a greater force?
Which object resists more?
Which accelerates most?
Ex. A block is pulled along a frictionless table by a
force that makes an angle q to the horizontal.
F
q
2.0
kg
a/ Find the x- and y-________________ of F.
b/ Replace F in the free body diagram with them:
F
y-direction: Because the block is not accelerating
up or down, the y-forces are ________________.
equilibrium:
w=
Notice: w _____ FN
x-direction: Only 1 force _________________
ax =
What will happen to a
if q is increased?
F
q
F
Fx ___creases,
so a ________
_____________.
Newton’s ______ Law:
In plain words:
For every_____________ ,
there is an equal and opposite____________.
In physics speak:
If object A exerts a __________ (the action) on
object B, then object B exerts a ___________ (the
reaction) that is ________________________ but
__________________________ on object A.”
A
B
Ex. Punching things:
Case 1: punching paper
force of paper
on fist:
force of fist
on paper:
Which object exerts a greater force?
Case 2: punching a cement block
force of block
on fist:
force of fist
on block:
Which object exerts a greater force?
Action-reaction forces are ______________ in
case 2, but both cases are opposite and _________ .
 Forces ALWAYS occur in __________ .
 Either force could be called the ___________.
 One force does not happen _____________
 Both forces occur at the ___________________.
A/ Both forces are the exact same ___________ .
Ex 1: F: Earth ________ you down with _________.
-F: You _______ Earth up with _________.
Notice the "same types:"
Both forces are ____________ .
Both forces are ____________
Ex 2:
F: You ________ right on wall
with a __________________.
-F: Wall __________ left on you
with a __________________.
Ex 3:
F: Wire ________ up on picture
with a _______________.
-F: Picture _________ down on wire
with a________________.
wall
hand
B/ Action:reaction pairs act on ______________
objects in _____________ directions.
 Action:
A exerts a F on
 Reaction:
___ exerts a -F on ____.
subject
Ex 1:
B.
object
direction
F:
Earth pulls you down with gravity.
-F:
______ pull _______ ____ with gravity.
____________
direction
Notice how subject and object are _____________ ,
and the directions are ________________ .
Ex 2:
F: You push right on wall with a normal force.
-F: ______ pushes ______ on ______ with a
normal force.
Ex 3:
F: Wire pulls up on picture with a tension.
-F: __________ pulls _________ on ________with
a tension.
In Sum: To find a reaction force, re-write with:
1. the same _________ of force (push/pull
and gravity/normal/tension, friction, etc); but,
2. reverse _____________ and _____________
and the _______________ of the force.
Action:
Reaction:
"A (subject)
" ____ (subject)
pulls/pushes
_________________
in a certain direction
in ___________ direction
on
on
B (object)
___ (object)
with a certain force."
with _____________force."
Which force, action or reaction, has a greater
magnitude?
Ex: Write the action (A) and reaction (R) pairs.
block
table
Case 1/ Between block and table:
A:
R:
Case 2/ Between block and Earth:
A:
R:
Which of these are contact forces?
Which are "at a distance" forces?
Ex: Weight is the force of Earth’s
___________ pulling ______________
on an object:
w = ____ = Earth pulls__________
on cat with a
________________ force.
What is the reaction force to a
cat's weight, w?
The _______ _______ _______
on ________ with a
__________________ force.”
Ex. Don’t confuse ___________ (which are always
equal and opposite) with ___________________
(which depend on _________ and usually are NOT
equal and opposite).
Ex: An apple and the Earth (not to scale)
gravitational F of
Earth on ________
apple: a =
gravitational F
of apple on _________
Earth: a =
=
≈
Same _____ but different _____ b/c different _____ !
________________:
A. Find the acceleration of a block of mass m
on a ______________ ramp that makes an angle q
with the horizontal.
a=
To determine a, you need ______, which means
you need the ___________ that act on the block.
To find the force that accelerates the block down
the incline, you need to choose new axes that are
______________ ( ) and __________________ ( )
to the plane’s surface.
Notice:
New
Axes:
FN
w
q
The incline
angle ____
is _________
as this one.
The__________________ and _________________
components of ____ are the sides of a ___________
triangle:
q
w
side
side
adj =
hyp
= ______ 
w┴ = ________
opp =
hyp
= ______ 
w|| = _________
Now return to the full
free body diagram
and replace ____ by
its ________________.
FN
w|| =
________
q
w┴ =
_______
w
____ is balanced by _____:  ___ = _________
___ is unbalanced and equals Fnet = ______________
So what is the acceleration a?
a = Fnet =
m
_______ =
m
_______
m
=
Notice that the result is independent of ________ .
Ex: Find the acceleration of a 0.4-N block down
a frictionless incline if the angle is 100.
a=
a=
a=
Test: release from rest:
d = vit + (1/2)at2
d=
a=
a=
a=
To see if the equation a = _________ makes
sense for the incline, see what happens when
q has the "_______________ " values:
Case 1: What is a if q = 900?
a=
_____
_____
=
=
Case 2: What is a if q = 00?
a=
=
=
900
B. Now solve the problem, but with the block
_________ or moving with __________________due to
_____________.
q
w
q
If the block is not moving, Fnet = ___ , which
means all forces must ____________________ .
FN = ____ = _________ (equilibrium as before).
Ff = ____ = _________ (now in __________________).
Ex. A 3.0-kg block rests on an incline that makes
an angle 300 to the horizontal. Determine the
magnitude of the normal force and the friction
force acting on the block.
w=
300
____ = __________
__________
FN = ____ = _________ = _____________ = __________
Ff = ____ = _________ = _____________ = __________
C. Summary of inclined plane basics
Without friction:
With friction and at rest
or constant v:
FN
FN
Ff
q
q
w
w
FN = ____ = _________
FN = ____ = _________
Fnet = ____ = _________
Ff = ____ = _________
___ = _________
Fnet = __
Ex: If there is friction, but the
block is ____________________ ,
it must be that _____ > _____ .
In that case, the net force
Fnet = ________
FN
q
w
Ex: Notice that the incline __________ or weakens
gravity because it is not _______________ , but only
the ________________________
that is pulling the block
along the __________
of the incline.
Final notes:
1/ On a horizontal
surface: FN = ____
w
BUT,
On an incline (either
with or w/o friction):
FN = w┴ = ______
and NOT:
FN = ____
q
w
2/ What happens to Ff and FN
if q is increased and the block
remains the same and at rest?
original
incline:
q
FN
w
Ff
w||
q
w
w┴
inc. q
FN __________
As _____
Ff ___________
increases:
w ____________
The force of_________________, Ff:
1. Ff = A ____________ force that ____________
motion. It is caused by the __________________
______________________________________ between
an object and _________________________.
2. Friction usually results in __________ when
motion energy is transferred to ______________ in
the object and its environment. This results in a
temperature _____________ or a _________________,
such as _____________.
Ex: car
skidding
on road
________ energy
heats up ______
and _________
molecules
Three basic types of friction:
A._____________ friction– due to collisions with
fluid molecules; increases with speed
Ex: _________________________________
B._____________ friction –reduces amount of
friction because there is less __________________
Ex: ___________________
C. ______________ friction – when two _______
_____________ slide past each other; what we
are going to learn most about.
most
least
force  __________  ___________  __________  force
All About ___________ Friction:
A 10-N object at rest:
10 N
Fnet =____
Now pull it with a 2 N
force but it doesn’t move:
10 N
pull
Fp = 2N
Fnet =____
Pull it with a 4 N force
and it still doesn’t move:
pull = 4 N
10 N
Fnet =____
When you increase the force
to 6.0 N, it _______________:
10 N
pull = 6 N
Fnet ___ 0
__________
_______ friction = _____
Once it starts moving, you only need a _______
pull to keep it moving at _____________________:
10 N
pull = 5 N
Fnet = ____
__________
__________ friction = _____
__________
friction Ff,k
___________
static Ff,max
Note:
1._____________ friction, Ff
friction when body is_______________
can be _____ amount up to _______________
static friction
2. Maximum static friction, __________
friction just before the object ________________
During static friction, the _________________
molecular _________ between the object and the
surface are ________________ microscopically, at
first a little, then __________________. As the
bonds reach the ________________ point,
_______________________ friction occurs.
3. _________ friction, Ff,k is the friction that occurs
when an object moves at ____________________ .
 always ___ the__________ static friction: Ff,max
 As it slides, the surface _________ are
constantly ____________ and________________
Ex: Same wooden box
a/ On different sides:
v
v
__________ Ff,k
b/ At different speeds:
v
v
__________ Ff,k
Ff,k is roughly independent of
a/ ________________ , and
b/ _______________ .
A graphical view of static vs. kinetic friction:
Ff
bonds
______
bonds ____________
and ______________
Static
___ can
be ____
value
in here
_________ Friction
Static _______ > _______
____________ Friction
In either static or kinetic friction, sliding friction
depends on two factors:
1. The____________________________ – waxed skis
on snow, rubber on dry concrete, etc
Usually, smoother surfaces  __________ friction
2. The force that________________________________
 This force is the ____________ force: ______
Block on
a table:
But press down
on the block:
F
FN = ______
FN =_________
These 2 factors are summed up in the equation:
Ff =
 m is called the _________________ of friction,
and is the Greek letter “______. ” It:
- describes effect of surface ______________ on Ff
- is usually _____________ for rougher surfaces
- has ____ units: m = _______  units _________
- has different values for:
1/ maximum static friction: _____
2/ kinetic friction : _____,
and with ____ > ____ .
From the PhysRT, page ___ :
Notice:
1.This should say
___________ Static
mk ___ ms
2.
For maximum static Ff,max, use:
For kinetic Ff,k, use:
Ff = ____ FN
Ff = ____FN
Ex: A 12,000-N crate is on waxed skis on snow.
Find the force needed to…1/ start it moving, and
2/ keep it moving at constant velocity
1/ max. static: Ff = mFN =
=
=
Ff = mFN =
2/ kinetic:
=
=
How would you answers change if another
2000 N were added to the sled?