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Force & Motion
Newton’s Laws of Motion
Motion
 Motion
 An object is in motion
if the object changes
position relative to a
reference point.
Speed with a direction is Velocity
 Speed
 The speed of an
object is the distance
it travels divided by
the time it takes to
travel the distance.
Speed = Distance/ Time
 Velocity
 The speed of an
object moving in a
particular direction is
called its velocity.
Acceleration
 Acceleration
 The rate at which the
velocity of an object
changes is called
acceleration.
Force is a push or pull exerted on an
object. When you exert a force on an
object, you can change the object’s
motion.
 Unbalanced Forces
 Balanced Forces
 Cause an object to
speed up, slow down,
start/stop moving, or
change direction.
 Balanced forces do
not change an
object’s direction.
Work = Force X Distance
 When you exert a
force on an object
that causes the
object to move,
you have done
work
Introduction to
Forces and Motion
Forces at work at an
Amusement Park
•Potential Energy
 Stored energy
 It can be released later to do work
 Two types
 Gravitational – energy due to
position
 Example: yo-yo in your hand
 Elastic – energy due to compression
or stretching.
 Example: wound up toy
• Kinetic Energy
 Energy of moving objects
 Examples: moving bike, running
water
Newton’s First Law:
Also Known as “The Law of Inertia”
Every object in a state of uniform motion tends to remain
in that state of motion unless an external force is applied
to it.
 Inertia put a planet in
motion and it will always
remain in motion unless
an external force acts
upon it.
 Gravity pulls the planet
towards the Sun to keep
it in orbit.
Newton's Second Law of Motion:
 The relationship
between an
object's mass m,
its acceleration
a, and the
applied force F
is F = ma.
Newton's Third Law of Motion:
 For every action there is an
equal and opposite reaction.
 An equal and
opposite reaction.