Download (Force/Mass/Accel) ppt

Force, Mass, &
Acceleration
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Sir Isaac Newton
Lived in England from 1642 to 1727
Physicist & mathematician
Formulated the basic laws of mechanics
(motion)
Discovered the universal law of
gravitation
Invented calculus (math used to solve
physics problems)
Before he was 30 years old
Newton’s Laws
A Short Biography
Elements of Physics: Motion, Force, and Gravity. United Learning. 2003. unitedstreaming. 3 October 2005 <http://www.unitedstreaming.com/>
Newton’s Laws of Motion
In the actual words:
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First Law: An object at rest will remain
at rest unless acted on by an
unbalanced force. An object in motion
will remain in motion with constant
speed and direction unless acted on by
an unbalanced force.
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law = INERTIA
Newton’s 1st Law is also known as the
law of inertia.
Inertia is the property of an object to
resist changing its state of motion.
The amount of inertia depends on the
mass of the object.
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Let's take a closer look at inertia
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Newton's Laws videos!
INERTIA
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An object with more
mass has more
inertia, or more
resistance to changes
in motion
an object with less
mass has less inertia,
or less resistance to
change in motion
DEMO TIME!!!
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Watch as the book stays on the table
even though the paper moves!
How does this show inertia?
Newton’s Laws of Motion
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Second Law: When there is a force
acting on an object, it will move in the
direction of the force:
 force increases acceleration
 mass resists acceleration
Newton’s Laws of Motion
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Second Law: The acceleration of an
object is directly proportional to the
force acting on it and inversely
proportional to its mass.
Acceleration
(m/s2)
a= F
m
Force (N)
mass (kg)
nd
2
Law
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Let's Watch the second Law
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Video!!
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Three things you can get from the
equation:
Force (newtons) causes acceleration.
 Mass (kg) resists acceleration.
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 The acceleration(m/s ) you get is equal
to the ratio of force over mass.
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DEMO TIME
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Volunteer to sit in the chair?
Watch as the volunteer moves in the
direction of my force?
How does this relate to law 2?
LAW 3
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Third Law: For every action force,
there is an equal and opposite
reaction force.
If you push off on the wall
The wall will exert an equal and
opposite force on you
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What does
Newton's 3rd law
say?? Video
DEMO TIME!!
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Another volunteer??
This time they will push themselves.
Which way did they move… opposite of
the force or in the same direction of
their force?
How does this relate to law 3?
Group ACTIVITY!!!
Try to match the motion with the
correct law.
What is a FORCE?
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A force is a push or a pull, or any
action that has the ability to
change motion.
Examples:
Contraction (pulling) of
muscles that make bones
move
pushing a grocery cart
lifting your backpack.
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Force Video
What is the difference
between Force & Weight
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Force is a push or a pull that can
change the motion of an object. It
is measured in Newtons.
Weight is the force caused by
Earth’s gravity that acts on the mass
of an object. It is measured in
Newtons.
How are Force and
Mass related?
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Force is a push or a pull that can
change the motion of an object.
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It is created when a mass is accelerated by
something like gravity
Mass is the amount of matter (stuff) in
an object
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mass is a basic property of all objects
mass resists the action of forces by making
objects harder to accelerate.
What is the difference
between Mass & Weight
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Mass is the amount of matter (stuff) in
an object
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Mass is the same everywhere in the
universe – it does not change
Weight is the force of Earth’s gravity
acting on the mass of an object.
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Weight can change at different places in
the universe depending on the gravity
Balanced forces
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When the forces
on an object are
balanced, the
force in one
direction exactly
matches the force
in the opposite
direction
Unbalanced forces
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forces are
unbalanced
when the force
acting in one
direction is
greater than the
force acting in
another
direction.
Equilibrium
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An object is in
equilibrium when
the forces acting
on it are balanced,
the net force is
zero, and there is
no change in
motion.
NET FORCE
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The net force is the sum of all the
forces acting on an object.
The net force on an object that is not
moving is zero.
This means that the forces acting on the
object are balanced
 the motion is not changing
 NO acceleration is occurring.
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REFLECTION QUESTIONS
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Describe each of Newton’s 3 laws of
motion
1lb = ______ newtons?
F= ? (equation?)
Give the units for force and acceleration
What happens when something is at
equilibrium?
What is a Net force?
Conversion from
pounds to newtons
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One pound is equal to
4.48 newtons.
Your weight in pounds =
______ lbs. x 4.48N/1lb.
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______ N (your weight in
newtons.)
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