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Newton’s Laws
An object at rest will stay at rest. An object in
motion stays in motion with the same speed and
direction unless acted upon by an unbalanced force.
The acceleration of an object is dependent upon
two variables. The net force acting upon the object
and the mass of the object.
For every action there is an equal and opposite
reaction.
Sir Isaac Newton
Newton’s First Law
An object at rest will stay at rest. An object in motion
stays in motion with the same speed and direction
unless acted upon by an unbalanced force.
For additional information visit:
http://www.physicsclassroom.com/mmedia/newtlaws/cci.html
Newton’s First Law Examples
•To dislodge ketchup from the bottom of a ketchup bottle, it is
often turned upside down and thrust downward at high speeds
and then abruptly halted.
•Headrests are placed in cars to prevent whiplash injuries
during rear-end collisions.
•While riding a skateboard (or wagon or bicycle), you fly
forward off the board when hitting a curb or rock or other
object that abruptly halts the motion of the skateboard.
• Can you think of more???
Newton’s First Law
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Newton’s Second Law
Newton's second law states that
the acceleration of an object is
directly related to the net force
and inversely related to its mass.
Force
Acceleration =
Mass
For additional information visit:
http://www.physicsclassroom.com/mmedia/newtlaws/efff.html
Newton’s Second Law
If the elephant weighs more and
experiences a greater downwards pull
of gravity compared to the feather,
why then does it hit the ground at the
same time as the feather?
2nd Law Explained
Remember the second law - the acceleration of
an object is directly related to the net force and
inversely related to its mass. When figuring
the acceleration of object, there are two factors
to consider - force and mass. The elephant
experiences a much greater force which will
produce larger accelerations. BUT the mass of
an object resists acceleration. Thus, the greater
mass of the elephant offsets the influence of
the greater force. It is the force/mass ratio
which determines the acceleration.
Newton’s Second Law
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Newton’s Third Law
For every action
there is an equal and opposite reaction.
For additional information visit:
http://www.allstar.fiu.edu/aerojava/rocket1a.htm
Newton’s Third Law
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Quick Demonstration
Try this:
•Press the side of your hand against the edge of a table.
Notice how your hand becomes distorted.
•Clearly, a force is being exerted on it. You can see the edge
of the desk pressing into your hand; you can feel the desk
exerting a force on your hand.
•Now press harder. The harder you press the harder the desk
pushes back on your hand.
•Remember this important point: You can only feel the
forces being exerted on you, not the forces you exert on
something else. So, it is the force the desk is exerting on you
that you see and feel in your hand.
Law application
Bob the Beaker hit a
rock while moving
on his skateboard.
Newton’s 1st Law
Newton’s 2nd Law
Newton’s 3rd Law
He tumbled and
broke.
Which law of
physics applies to
this situation?
Why Newton’s
st
1
Law?
Bob the beaker is traveling 10 miles an
hour on his skateboard and being in
motion, he wants to stay in motion.
When his skateboard stops due to the
rock, Bob still wants to carry on the
motion and he falls.
An object in motion stays in motion with the same speed
and direction unless acted upon by an unbalanced force.
Law application
Newton’s 1st Law
Newton’s 2nd Law
Newton’s 3rd Law
During the 9th inning of the
World Series, New York
Yankee Roger Clemens
pitches the ball and Atlanta
Brave Kevin Millwood hits
the ball out of the park for a
homerun.
Which law of physics applies
to this situation?
Why Newton’s
rd
3
Clemmons’ baseball forces
Millwood’s bat to the right
(an action) when they meet;
the bat forces the ball to the
left (the reaction).
For every action there is an
equal and opposite reaction.
Law?
Law application
Newton’s 1st Law
Newton’s 2nd Law
Newton’s 3rd Law
You are helping rearrange your
living room furniture. You
push with all you strength and
easily move the chair to it’s
new spot in the corner. You
then push with all you might to
move the couch to it’s new spot
but it barely moves. Which law
of physics applies to this
situation?
Why Newton’s 2nd law?
Newton’s 2nd law of motion states that
acceleration depends on two factors – force &
mass.
Acceleration = Force / Mass.
This means the mass of an object has a negative
effect on acceleration. Simply put if an object
has more mass it will be harder to move.
(force has a positive relationship; more force more acceleration)