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Forces
Force
•A force is a push or pull on an object
resulting from the object's interaction with
another object.
•This push or pull results in a change of
direction and/or velocity (speed).
Types of Force
•The normal force is the force that opposes
the force of gravity, and keeps you from
falling through the floor. It is perpendicular to
the surface.
Types of Force
• Gravity is a force that
pulls objects downwards
towards the center of the
earth. It is a fundamental
force.
Going down hill on
skis, a bike or a
skateboard is a result
of gravitational force.
Types of Force
• Friction is the
resistance between
two surfaces that
are in contact with
each other.
Frictional force is
what keeps this rock
climber from slipping
off the rock.
Types of Force
• Air resistance pushes against things which are
moving.
The wind you feel on your face when you
ride a bike is a result of air resistance force.
Types of Force
• Pressure is the force that acts on a unit area of
surface due to compression of fluids.
The feeling in your ears when you dive to
the bottom of a pool, fly in an airplane or drive
over a mountain pass is a result of pressure
force.
14,000’
9000’
1000’
This plastic bottle, filled
with air, was sealed at
14,000’ above sea level
and then taken down to
1000’ above sea level.
Types of Force
• Buoyant force is the force of a fluid that
pushes an object up and makes it seem to lose
weight in that fluid.
The feeling of weightlessness in water is a
result of buoyant force
Types of Force
• Tension is the force which is transmitted
through a string, rope, or wire when it is pulled
tight by forces acting from each end.
Tension force is the force responsible for
you winning (or losing) a game of tug-of-war.
Types of Force
• Spring force is the force exerted by a
compressed or stretched spring upon any object
which is attached to it. An object which
compresses or stretches a spring is always
acted upon by a force which restores the object
to its original position.
The fun you have on a trampoline or pogo
stick or the soft ride on a bike with shock
absorbers is a result of spring force.
Types of Force
• Electromagnetic Force is the force exerted by
polar charges. It is a fundamental force.
EM Force holds together atoms and
molecules and gives strength, shape and
hardness to matter.
Balanced Forces
• Balanced forces act equally and opposite of
each other. Objects don’t change velocity or
direction because of balanced forces
Unbalanced Forces
• Unbalanced forces are needed to make
things change velocity and/or direction.