Transcript FORCES - Mr. Maloney

Objectives
You will be able to …
 Differentiate and describe the various
types of forces we will be using in class.
Examples of Forces

Contact
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
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
Applied Force (Fa, F#)
Tension (FT, T)
Normal Force (FN, N)
Friction Force (Ff, f)
Air Resistance (Fair)
Spring Force (Fsp)
At a Distance
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Gravitational Force (Fg)
Electrical Force (FE)
Magnetic Force (FM)
Nuclear Forces
Examples of Forces

Contact







Applied Force (Fa, F#)
Tension (FT, T)
Normal Force (FN, N)
Friction Force (Ff, f)
Air Resistance (Fair)
Spring Force (Fsp)
At a Distance




Gravitational Force (Fg)
Electrical Force (FE)
Magnetic Force (FM)
Nuclear Forces
Applied force [f#, fa, fb, f??]
 Just
any generic force in a problem
 Usually named after the object
FJeska
applying it.
 FBob
 FJeska
 Fdog
 Fpole
 Fwall
 FA …
FB … F17
Tension force [t, ft]
 An
applied force where the
force is applied through a
string, cable, rope, etc.
 Special in the fact that a
tension force can only pull, it
cannot push.
 We usually assume the tension
in a cable is the same
everywhere in the cable.
Normal force [fN]
 Contact
interaction force
between surfaces.
 Always acts
perpendicular to the
surfaces and out of the
surface.
 Comes from the
microscopic deformation
of molecules modeling a
system of springs.
FN
Friction force [ff]

Comes from interactions with a surface as an
object moves (kinetic) or tries to move (static)
relative to the surface.
 Depends on the normal force and a surface
interaction constant called the coefficient of
friction [].
Ff    FN

Always acts opposite the direction of motion.
Ff
Ff
Surface
Air resistance force [fair]

Force that acts in a
direction opposite
motion through a gas.
 Comes from
cumulative interaction
with air molecules.
 Increases as the
velocity through the
gas increases.
 Increases as the area
normal to the direction
of motion increases.
Spring force [fsp]

Comes from displacement of molecules.
 Spring Force is always opposite the
displacement of the spring.
 A Force from a Hookean Spring is proportional


to the displacement of the spring [x]
to the spring constant [k] (stiffness)


Fsp  k  x
Gravitational force [fg]

At a Distance Force of
attraction between ALL
massive objects.
FG  m  g

Local gravitational
constants
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gEarth: 10 N/kg.
gMoon: 1.6 N/kg
gJupiter: 26 N/kg
gyou: ~0.000000005 N/kg
FG,blue
FG,orange
FG,red
FG,green