Download Newton`s laws of motion

Studying
Newton’s Three Laws of Motion
Sir Isaac Newton
(January 1643 –March 1727)

Newton's laws of
motion are three
physical laws which
provide relationships
between the forces
acting on a body and
the motion of the
body.
Newton’s First Law…
An object at rest will
remain at rest- unless
acted upon by an
outside force.
Newton’s First Law
An object in motion
will remain in motion
– unless acted upon
by an outside force.
Chapter 6
Newton’s First Law of Motion
An object at rest remains at rest, and an object in
motion remains in motion at a constant speed and in a
straight line unless acted on by an unbalanced force.
Chapter 6
Newton’s First Law of Motion, continued
The First Law is Also Called…
The
Law of Inertia
 Inertia
is a resistance to change in
motion.
Can You Explain ?
Examples…
An object at rest will
remain at rest.
1.
Activity # 1
2.
“Freefall”
The Tablecloth Trick
An object in motion will
continue to move in a
straight line.
For Example…
The Story of Fluffy
Poor Baby Barbie
Anti- Inertia Belts
Better known as
“Seatbelts” !
Chapter 6
Newton’s Second Law of Motion
The acceleration of an object depends on the mass of
the object and the amount of force applied.
• Newton’s second law describes the motion of an
object when an unbalanced force acts on the object.
Newton’s Second Law
This Law shows the
relationship between
mass, force, and
acceleration.
When a force is applied
to a mass, it
accelerates.
The larger the mass of an
object, the more force needed
to start it, stop it, or change its
direction.
A speeding bullet and a slow moving train both have tremendous force.
The force of the bullet can be attributed to its incredible acceleration
while the force of the train comes from its great mass.
Chapter 6
Newton’s Second Law of Motion
The acceleration of an object depends on the mass of
the object and the amount of force applied.
• Newton’s second law describes the motion of an
object when an unbalanced force acts on the object.
Chapter 6
Newton’s Second Law of Motion
• Part 1: Acceleration Depends on Mass The
acceleration of an object decreases as its mass
increases. Its acceleration increases as its mass
decreases.
• Part 2: Acceleration Depends on Force An object’s
acceleration increases as the force on the object
increases. The acceleration of an object is always in
the same direction as the force applied.
Chapter 6
Section 2 Newton’s Laws of Motion
Chapter 6
Section 2 Newton’s Laws of Motion
Newton’s Second Law
For Example:
A Bowling Ball vs a
ping pong ball.
Or Runaway Ramps
Choose Your Position..
Some Athletes are
long and lean, with
little body fat, and
little muscle.
Basketball players
and wide receivers
fit this category.
Choose Your Position…
Other athletes, on
the other hand, have
lots of body fat, lots
of muscle, and gain
weight easily.
Football lineman
and sumo wrestlers
are heavier and
rounder individuals
Momentum, Mass, and Velocity
• The momentum of an object is the product of the
object’s mass and velocity. Object at rest has zero
momentum.
Calculating Momentum The relationship of
momentum (p), mass (m) in kilograms, and velocity (v)
in meters per second, is shown in the equation below:
pmxv
What is
(i) the total kinetic energy before the collision;
(ii) the total kinetic energy after the collision.
(iii) the total loss in kinetic energy.
The Law of Conservation of Momentum
• The law of conservation of momentum states that any
time objects collide, the total amount of momentum
stays the same.
The Law of Conservation of Momentum
• The combined objects have a different velocity
because momentum is conserved and depends on
mass and velocity.
• So, when the mass changes, the velocity must
change, too.
The Law of Conservation of Momentum,
continued
• Objects Bouncing Off Each Other When two
objects bounce off each other, momentum is
transferred from one object to the other.
• The transfer of momentum causes the objects to
move in different directions at different speeds.
The Law of Conservation of Momentum,
continued
• Conservation of Momentum and Newton’s Third
Law Conservation of momentum can be explained
by Newton’s third law.
• Because action and reaction forces are equal and
opposite, momentum is neither gained or lost in a
collision.
Forces Always Come in Pairs
.
Newton’s Third Law of Motion
Whenever one object exerts a force on a second
object, the second object exerts an equal and opposite
force on the first.
• Newton’s third law of motion can be simply stated as
follows: All forces act in pairs.
Newton’s Third Law

For every action force,
there is an equal, but
opposite, reaction
force.
The Action Force is Equal in
size but Opposite in Direction.
Action and Reaction forces
always act on different
objects.
Action Force: The man
pushes against the
wall.
Reaction Force: the wall
pushes on the man.
Newton's third law does not mean that forces always cancel out
so that nothing can ever move. If these two figure skaters,
initially at rest, push against each other, they will both move.
Another example: Recoil of a
gun or cannon
Or…Launching a Rocket

Or… a Lawn Sprinkler