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Types of Forces
A Time for Physics First
Summer 2010
What is a Force?
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A force is nothing else than a push or a
pull.
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A force applied to an object might change
its shape (deformation)
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A force applied to an object might affect
the object’s motion
Categories of Forces
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Contact forces – require the agent that
causes the force to be in contact with the
object.
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Field Forces – act at a distance.
Field Forces
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Gravity (Fg) – force created by the mass
of an object being affected by gravity
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holds stars, planets together; depends on the
mass of objects.
Electromagnetic (Fm)(magnetic)–
responsible for binding of atoms and
molecules; depends on the charge on
objects.
Static-Electric (Fs) An accumulation of electric charge on an
insulated body.
Gravitational Forces
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Gravitational forces occur because
objects have mass
Gravitational forces act
on all objects!
Contact Forces
Friction Force (Ff)
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Frictional forces between two objects
depend on the type of surfaces that are in
contact with each other
Air Resistance Force (Fair)

Frictional forces between an object and
the air going over the object.
https://www.youtube.com/watch?v=o2xmAWS4akE
Elastic Force (Fe)

An elastic force applied to an object
deforms the object but once removed
allows the object to recover its original
form, length, shape.
Tension Force (Ft)

The force that shows up in a string/rope
as the result of pulling it is called tension
force
Buoyant Force (Fb)

When a solid object is submerged in a
fluid (completely or partially), there exits
an upward force on the object that is
equal to the weight of the fluid that keeps
the object floating.
Normal or Support Force (Fn)

Support force between and object and a
surface; it is always perpendicular to the
surface at the point where the object
touches it
Push/Pull Force (Fp)

Any force on an object that is resulted by
one object pushing or pulling on another
object.
Forces - summary
FG or Fg
Fm
Fs
Fw
Fe
Fair
Ff
Fp
FT
FB
FN or Fn
Gravitational force
Magnetic
Static-electric
Weight
Elastic force
Air Resistance Force
Friction force
Push/Pull force
Tension force
Buoyant force
Normal force
Field force
Field force
Field force
Field force
Contact force
Contact force
Contact force
Contact force
Contact force
Contact force
Contact force
Analyzing forces

A force is produced by an agent.
No agent, means no force!!!

A force acts on an object – the receiver.

The force causes something to happen –
the effect.
Analyzing Forces – Example 1
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Receiver: child
Agent: Earth
Force: gravity
Effect: comes down
Receiver: child
Agent: slide
Force: friction
Effect: slows down
Analyzing Forces – Example 2
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Receiver:
Agent:
Force:
Effect:
dog
man
tension
pulling
Receiver:
Agent:
Force:
Effect:
dog
ground
normal
holds up the dog
Analyzing Forces
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Determine the object that is the receiver.
Identify the agents (objects that apply forces to
the receiver).
For each agent, identify the force it applies.
Represent the direction of the force with an
arrow starting on the receiver.
Describe the effect of the identified forces on
the receiver.
Analyzing Forces – Practice 1
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Receiver:
Agent:
Force:
Effect:
table
Earth
gravity
Table pulled
down
Analyzing Forces – Practice 2
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Receiver:
Agent:
Force:
Effect:
boy
chair
normal
Boy is
supported