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Factors Influencing Movement
1. Magnitude of F or T
2. Inertial characteristics of object such as it’s
mass, friction factors
3. Pathway available
Linear Speed
Scalar quantity
how fast only
s = d/t
Donavan Bailey 100m
9.84
Michael Johnson 200m
10.11 + 9.12
Linear Velocity
Vector quantity
how fast and in what
direction
v = d/t
stride length x stride
frequency
Stride Length & Stride Frequency
changes
with running velocity
FIGURE 10-3 on page 324
“Basic Biomechanics” 4th edition by Susan J. Hall
Page 280 from course text
Johnson vs Bailey
• at 5.6 seconds in 150m Match Race:
Bailey 25 strides (4.46 strides per sec)
Johnson 27 strides (4.48 strides per sec)
• at 1996 Olympics:
Bailey 9.84 for 100m
(avg v = 10.16mps)
Johnson 9.22 for 2nd 100m (avg v = 10.84mps)
• Fastest recorded 10m segment in 100m race is 0.83
seconds giving a velocity of 12.1mps / 43.5km per hr
Linear Acceleration
•
•
•
•
•
Vector quantity
changing speed OR changing direction
a = (v2 - v1)  (t2 - t1)
2 is final and 1 is initial (velocity & time)
a is directly related to Force and only occurs
when Force is applied or ceases
• speeding up =
+ slowing down = -
Universal Gravitation - Newton
1. Direct relationship between mass of 2 bodies
and force of attraction between them
2. Indirect relationship between distance squared
between 2 bodies and force of attraction
between them
3. Falling bodies “attracted” to the ground by
gaining speed @ 9.8mps per second
4. Upward projected bodies slow as above
Zero Velocity
Zero Acceleration
Body at rest
1. Body at rest
OR
No motion
2. Body moving @ constant v
OR
3. Body not changing direction
Constant v
No change
rare in sport
Figure F.2 page 280
Terminal v
skydiving
air = resistive Force
g = motive Force
F resistive = F motive
Average v
usually not a concern
in study of motion
v = d/t
40-50m in 1.11sec.
average v = 9.01mps
1000m in 3:30min.
average v = 4.76mps
Instantaneous v
at a given point
takeoff
release
impact
Figure F.3 page 281
INERTIA - Newton’s 1st Law
• “resistance then persistence”
1. body at rest remains so until a net Force acts to
accelerate the body
2. body moves in the direction of applied Force @
constant v until
- that Force is changed in magnitude or
- a Force from another direction is applied
Projecting Objects
Muscle torques are motive Force
Air resistance is a resistive Force
gravity resistive Force then motive Force
friction may be a resistive Force
ACCELERATION
Newton’s 2nd Law
 Inertia = sluggishness/resistance to change
 Inertia is directly related to mass
 a = F/m
 a has a direct relationship with F
 a has an indirect relationship with m
F centripetal
Reaction
• Inward seeking
•
• exerted along the
path of the radius of
the arc
•
• Fc = ma (radial)
Body wants to continue
on original path
greater m or v requires
greater friction/grip
Pushing outward to get sufficient inward
F centripetal to stay on the desired curved path