definition of force
DESCRIPTION
Definition of Force. Drawing the Force. Dimensions and Units of Force. Tension. Elastic Force. Gravity. Normal Force. Friction. Drag. Pulleys. Force That which causes a particle to accelerate. It is a vector! Knight’s Definition A force … is a push or a pull on an object. - PowerPoint PPT PresentationTRANSCRIPT
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
1
Definition of Force
Drawing the Force
Dimensions and Units of Force
Tension
Elastic Force
Gravity
Normal Force
Friction
Drag
Pulleys
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
2
Force
That which causes a particle to accelerate.It is a vector!
Knight’s Definition
A force …
is a push or a pull on an object.It is a vector. It has both magnitude and direction.It requires an agent. Something does the pushing or pulling.It is either a contact force or a long-range force (gravity).
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
3
Force, like any vector is drawn as an arrow with the symbol or magnitude and units.
The tail of the force is placed on the part of the object that is experiencing the force.
In a free-body diagram, the tail is placed on the point representing the particle.
The direction of the force and its magnitude are determined by the type of force it is.
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
4
Force
The SI unit of force is the Newton (abbreviated as N).
One Newton is the same as one kilogram-meter per second squared.
Another unit of force is the pound.
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
5
Tension
The magnitude of the tension is the same everywhere in the rope.
T
T
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
6
Name of Force
Symbol
When does this force occur?
Where does this force occur?
Magnitude
Direction
Associated Energy
Tension
If an object that is experiencing the force is pulling but not stretching another object
On the object that is experiencing the force at the point where the pulling occurs
Determined using Newton’s Second Law
Toward the center of the object being pulled (rope, wire, etc.)
No associated energy
T
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
7
Spring Force
xk
spF
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
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Name of Force
Symbol
When does this force occur?
Where does this force occur?
Magnitude
Direction
Associated Energy
Spring Force
On the object experiencing the force where it connects to the object that stretches/compresses
Toward the center of the object that stretches or away from the center of the object that compresses
Elastic Potential Energy
If an object that is experiencing the force is stretching (or compressing) another object
springF
xk
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
9
Gravity
GF
GF
r
1m
2m
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
10
Name of Force
Symbol
When does this force occur?
Where does this force occur?
Magnitude
Direction
Associated Energy
Gravity
or
At the center-of-mass of the object receiving the force
or
Toward the center of mass of the other massive object
Gravitational Potential Energy
If there are two massive objects present
GF
w
221
r
mmG mg
2
211
kg
Nm 1067.6 G
2s
m 81.9g
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
11
Gravity (near the earth’s surface)
m
Mass of the earth 6x1024 kgRadius of the earth 6.375x106 m
mgm
m
R
mGMF
e
e
226
242
211
2 s
m81.9
m 106.38
m 1099.5kgNm
1067.6
ˆ w mg j
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
12
Normal Force
m
N
m
N
w
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
13
Name of Force
Symbol
When does this force occur?
Where does this force occur?
Magnitude
Direction
Associated Energy
Normal Force
or
If an object touches the surface of another object
On the object receiving the force at the point(s) where it touches the surface
Determined using Newton’s Second Law
Perpendicular to the surface and from the object exerting the force to the object experiencing it
No associated energy
NFn
, N
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
14
Friction
m
N
f
Direction of motion
or possible motion m
N
f
Direction of motion
or possible motion
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
15
Name of Force
Symbol
When does this force occur?
Where does this force occur?
Magnitude
Direction
Associated Energy
Friction
or
If an object touches the surface of another object
On the object receiving the force at the point(s) where it touches the surface
or
In a direction that opposes the motion or the possibility of motion
Thermal Energy
sf
kf
Ns Nk
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
16
Drag
D
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
17
Name of Force
Symbol
When does this force occur?
Where does this force occur?
Magnitude
Direction
Associated Energy
Drag
If an object is moving through a liquid or gas.
On the object receiving the force at the point(s) where it touches the liquid or gas
In a direction that opposes the motion
Thermal Energy
D
2
2 kg/m 4
1Av
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
18
Pulleys
Pulleys simply change the DIRECTION of a force.
T
T
College and Engineering Physics
Types, Directions and Magnitudes of the Forces
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