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Forces Notes
“Any influence that can cause a body to be
.”
It is measured in
A
second
A
.
is the force needed to accelerate one kg one meter per second per
or
exerted by an object to/on another object
Always occurs in
(Sometimes referred to as Agent & Receiver)
It can alter the
or
of an object
It is represented by
that show
Demos
and size
What it demonstrates
Rolling Ball
Pushing a closed door
Standing on the floor
Clay ball
Tennis ball
Pushing on a table
Newton’s Laws of Motion
Law #1:
“Every body continues in its state
of
, or of
uniform motion in a straight line,
unless it is compelled to
by forces impressed upon it.”
that state
Sometimes called the Law of
Who is this?
What is Inertia?
“The sluggishness or apparent
a body offers to changes in its state of motion”
The larger the
, the larger its
A body with less
is easier to get moving
A body with more mass is
to get moving
Demos
What it demonstrates
Ping pong ball
Bowling ball
Granny
Mack Truck driven by Granny 
Mass
Defined as “The quantity of
in a body”
It is the measurement of
m = mass; F = force; a = acceleration
= F/a
= m(a)
Why should Eeyore ALWAYS wear a
seatbelt?
= F/m
Momentum
The product of
It is
Demos
Car on a ramp
Eeyore on a car on a ramp
and
in motion
What it demonstrates
Conservation of Momentum
All energy stored in a moving object is not
, but only
form
Stated by:
Demos
What it demonstrates
Newton’s Cradle
Swinging Rock
Mass in a Circular Motion
When an object moves in circular path, it has a property called
AKA:
Inertia
Inertia
“An object rotating about an
tends to remain rotating about that same axis
unless it is interfered with by some external force.”
This definition is similar to Newton’s
Demos
What it demonstrates
Bicycle tire
Gyroscope
Top
Frisbee
Football
Moment of Inertia
Angular Momentum
It is a measure of an object’s rotation
about a particular
For an object small compared to the radial distance, it is
the product of mass, velocity and radius (
x
x
It is the measure of the rotational property
of
It is
the centripetal force
to
)
Describe what’s happening in this diagram:
Demos
What it demonstrates
Rolling objects
Washer on a string
Slingshot (old-fashioned!)
Bucket with water spun in vertical circles
Q: What holds the water in the bucket?
Spin cycle of washing machine
“Whizzer”
Brendan on the Scrambler
Carnival Ride Know-How
It’s better to take the
of the car if you’re riding alone
If you’re riding with someone
else, take the
seat
seat
The following formula is similar to those
for Newton’s
, but
deals with mass in motion in a circular path: mvr = mvr
m=
What was demonstrated to show what happened
here?
v=
r=
What happens in this situation?
mv
r = mvr
… The mass is not affected by a smaller radius, while
is.
Centripetal Force
A center-seeking
that causes an object to follow a circular path.
“Any force that is directed at
produces circular motion.”
to the path of the moving body and
Name the centripetal force that keeps the moon
revolving around the earth:
Centrifugal Force
A fictitious
due to rotation
force
It is a
to centripetal
force but there is no agent, therefore it is experienced
relative to position
What we are really experiencing is
!
Newton’s Second Law
The acceleration of a body is
the body and
proportional to the net force acting on
proportional to the mass of the body and is in the
direction of the NET
Formulas:
= F/m
5N
Acceleration = 6 kph
= m (a)
= F/a
5N
5N
Acceleration = _____
Acceleration = _____
N
Newton’s Third Law
Whenever one body exerts a
on a second body, the
second body exerts an
and opposite force on the first
For every
, there is an equal and opposite reaction
You cannot
without being
Common Forces
Gravitational – non contact
5 Every object exerts an
N
Buoyancy - contact
The tendency to
Acceler
ation = ?
force on every other object
in a fluid
Friction - contact
The
to motion where two objects touch
Magnetic – non contact
The repelling or
of a magnet and ferromagnetic material
Elastic - contact
Ability to
to its original size, shape, or position after
being stretched, squeezed, flexed, expanded, etc.
Electrical – non contact
Flow or gathering of a negative charge by
P
K
P
K
Other Physics concepts of interest:
Energy
The quality of an object that enables it to do
Power
Work/ Time
Potential Energy
The
energy that a body
possesses because of its position with respect to other bodies
Kinetic Energy
The energy of
Kinetic Energy = 1/2 mv2
At which point is potential and kinetic
energy equal?