Februar
nd
y 22
ACAP
Review 1
(Google
Form)
ALCOS 8, 9,
10:
•
•
1.ACAP Review form
(Do Now)
2.Discuss project and
ask questions about
project
3.Begin NL notes
BHM Research projects are due Sunday!
4.Begin
incompleting
class ACAP
Make sure you are
the review
slides (ACAP Review)
review
Newton’s Laws of
Motion
Things to look for in your
notes:
• Vocabulary words are going to
be green
Newton’s Laws of Motion
• 1st Law – An object at rest will stay at
rest, and an object in motion will stay in
motion at constant velocity, unless acted
upon by an unbalanced force.
• 2nd Law – Force equals mass times
acceleration.
• 3rd Law – For every action there is an
equal and opposite reaction.
Newton’s First Law
“The velocity of an object will remain constant
unless a net force acts on it.”
1st Law – An object at rest will stay at
rest, and an object in motion will stay in
motion at constant velocity, unless acted
upon by an unbalanced force.
Basically, an object will “keep doing what it was
doing” in the same direction at the same speed
unless acted on by an unbalanced force.
• If the object was sitting still, it will remain
motionless. If it was moving at a constant
velocity, it will keep moving.
• It takes force to change the motion of an
object.
What is meant by unbalanced
force?
• If the forces on an object are equal and
opposite, they are said to be balanced, and the
object experiences no change in motion.
• If they are not equal and opposite, then the
forces are unbalanced and the motion of the
object changes.
Newton’s First Law is also called the
Law of Inertia
Inertia: the tendency of an object to
resist changes in its state of motion
• The First Law states that all
objects have inertia.
• The more mass an object has, the
more inertia it has (and the harder
it is to change its motion).
**Therefore, inertia depends on mass.**
Mass & Inertia
If an object has a large amount of
inertia (due to a large mass)
1. It will be hard to slow it down or
speed it up of it is moving.
2. It will be hard to make it start
moving if it is at rest.
3. It will be hard to make it change
direction.
INERTIA DOES NOT DEPEND ON
GRAVITY
• An object’s inertia is the same on Earth
as it is in space.
Examples of the effects of inertia
might also include:
1. Inertia causes a passenger in a
car to continue to move forward even
though the car stops. This is the
reason that seat belts are so important
for the safety of passengers.
NOTE: Inertia is the reason that it is
impossible for vehicles to stop
instantaneously.
Don’t let this be you. Wear seat belts.
Because of inertia, objects (including you)
resist changes in their motion. When the car
going 80 m/hour is stopped by the brick
wall, your body keeps moving at 80 m/hour.
2. Inertia is the reason that it is harder
to
start pushing a wheelbarrow
full of bricks than to start pushing an
empty wheelbarrow.
The filled wheelbarrow has more mass and therefore, more inertia.
3. Inertia is also the reason that it is
harder to stop a loaded truck going 55
miles per hour than to stop a car going
55 miles per hour.
The truck has more mass resisting the change of its motion and
therefore, more inertia.
If objects in motion tend to stay in
motion, why don’t moving objects keep
moving forever?
Things don’t keep moving forever because
there’s almost always an unbalanced force
acting upon it.
A book sliding across a table slows
down and stops because of the force
of friction.
If you throw a ball upwards it will
eventually slow down and fall
because of the force of gravity.
What is this unbalanced force that acts on an
object in motion?
• There are four main types of friction:
– Sliding friction: ice skating
– Rolling friction: bowling
– Fluid friction (air or liquid): air or water
resistance
– Static friction: initial friction when
moving an object
In outer space,
away from
gravity and any
sources of
friction, a
rocket launched
with a certain
speed and
direction would
keep going in
that same
direction and at
that same speed
forever.
Momentum
Momentum
• Momentum is what Newton called the
“quantity of motion” of an object.
• Momentum is a characteristic of a
moving object that is related to the
mass and the velocity of the object.
Momentum
• The momentum of an object:
• Depends on the object’s mass
and velocity
–What is velocity?
• Velocity includes the speed and
the direction. Ex: 10mph north
How does momentum
relate to inertia?
• Momentum is similar to inertia.
Like inertia, the momentum of
an object depends on its mass.
• Unlike inertia, however,
momentum considers how fast
the object is moving.
Newton’s
ND
(2 )
Second Law
Force equals mass times acceleration.
Acceleration: a measurement of how
quickly an object is changing speed
and direction (velocity) per unit time.
__________
__________
MORE MASS NEEDS MORE FORCE
FOR GREATER ACCELERATION
Newton’s Third Law
“Law of Action and Reaction”
For every action, there is an
equal and opposite reaction.
3rd Law- Meaning????
According to Newton,
whenever objects A and B
interact with each other,
they exert forces upon
each other. When you sit
in your chair, your body
exerts a downward force
on the chair and the
chair exerts an upward
force on your body.
3rd Law in Action
• Birds depend on
Newton’s third law
of motion.
•
As the birds push
down on the air with
their wings, the air
pushes their wings
up and gives them
lift.
Think about it . . .
What happens if you are standing on a
skateboard on a slippery floor and push
against a wall? You slide in the
opposite direction (away from the
wall), because you pushed on the wall
but the wall pushed back on you with
equal and opposite force.
Why does it hurt so much when you
stub your toe? When your toe exerts
a force on a rock, the rock exerts
an equal force back on your toe.
The harder you hit your toe against it,
the more force the rock exerts back on
your toe (and the more your toe
hurts).
Other Examples of Newton’s
3rd Law of Motion
More Examples of the 3rd Law
Let’s Recap The Laws of
Motion