Download Laws of Force

Laws of Force
Mr. Dunnum
Physical Science
What is force?
 Force is simply a push or pull
 All forces have both size and direction
 Forces are everywhere
 Anytime you see something moving, you
can be sure that its motion created by a
force
How do we measure force?
 Scientist express force
by using a unit called
Newton's
 The more the
Newton's the greater
the force
Net force?
 What is net force?
 Net force is the result of combining all the forces
exerted on an object
 Same direction you add them
 Opposite directions you subtract them
Unbalanced and Balanced
Forces
 Unbalanced forces
 When the net forces
of an object is not
zero then it is an
unbalanced force.
 Unbalanced forces
cause nonmoving
objects to start
moving
Balanced forces
When the net forces
equal zero then the
forces are balanced
Balanced forces don’t
cause objects to move
Newton's first law
 If an object is at rest it will remain at rest
unless it is affected by an outside force, if
an object is moving it will remain moving
until it is stopped by an outside force.
Friction
 Force that opposes motion
between two surfaces
 Friction occurs because
the surface of any object
is rough
 A rougher surface creates
more friction
 The more force the more
friction
Sliding/ Rolling Friction
 Sliding Friction
 Takes more effort and
force to move objects
by sliding
 Ex. Moving furniture
Rolling Friction
Is important to all means
of transportation
The friction is smaller
and easier to move
than sliding
Fluid/Static Friction
 Fluid Friction
 Also less than sliding
friction
 Swimmers have to
overcome this when
swimming
Static Friction
Prevents an object from
moving when force is
applied
Ex. Moving a
refrigerator
Helpful/Harmful
Friction
 Helpful
 Car- friction helps push the car down the
road.
 It also helps us stop the car with the brakes
 Harmful
 Car- Cause wear and tear on the motor of
the car.
Newton's Second Law
 An object acted upon by a force will
accelerate in the direction of the force
 Acceleration= net force
mass
F=MA
What is Gravity?
 Gravity is the force of
attraction between
two objects
 All matter is affected
by gravity
 Gravity pulls you
down, air resistance
pushes you up
Gravity Con.
 Small masses have a small gravitational
force
 The larger masses have a larger
gravitational force
 If the distance between the two objects is
in creased then the gravitational force is
reduced
Weight and Mass
 Weight
 Weight is the
gravitational force
exerted on an object
 Weight changes when
the gravitational force
changes
 Weight is measured
on a spring scale
Mass
The amount of matter in an
object, and its value does
not change
If moved to Jupiter the
weight would change, but
not the mass
Measured by a balance
Newton's Third Law
 For every action there is an equal, but
opposite reaction
 Example when you push a wall it pushes
back with the same force
Examples of Newton’s 3rd Law
 Bumper cars
 Getting oil changed
 Diving in a pool
 Dunking a basketball
Free fall and Weightlessness
 Free Fall
 An object is in free
fall when the only
force acting on it is
gravity
Weightlessness
Is the condition that
occurs in free fall
when the weight of an
object seems to be
zero