Factors Influencing Movement

1
Factors Influencing Movement

• 1. Magnitude of F or T
• 2. Inertial characteristics of object such as
  its mass, friction factors
• 3. Pathway available

2
Linear Speed Linear Velocity

• Scalar quantity
• how fast only
• s d/t
• Donavan Bailey 100m9.84
• Michael Johnson 200m10.11 9.12

• Vector quantity
• how fast and in what direction
• v d/t
• stride length x stride frequency

3
Stride Length Stride Frequency changes with
running velocity
FIGURE 10-3 on page 324Basic Biomechanics 4th
edition by Susan J. Hall
4
Page 280 from course text
5
Johnson vs Bailey

• at 5.6 seconds in 150m Match RaceBailey 25
  strides (4.46 strides per sec)Johnson 27
  strides (4.48 strides per sec)
• at 1996 OlympicsBailey 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

6
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 -

7
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 _at_ 9.8mps per second
• 4. Upward projected bodies slow as above

8
Zero Velocity Zero Acceleration

• Body at rest
• No motion

• 1. Body at restOR
• 2. Body moving _at_ constant vOR
• 3. Body not changing direction

9
Constant v Terminal v

• No change
• rare in sport
• Figure F.2 page 280

• skydiving
• air resistive Force
• g motive Force
• F resistive F motive

10
Average v Instantaneous v

• usually not a concern in study of motion
• v d/t
• 40-50m in 1.11sec. average v 9.01mps
• 1000m in 330min. average v 4.76mps

• at a given point
• takeoff
• release
• impact
• Figure F.3 page 281

11
INERTIA - Newtons 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 _at_
  constant v until - that Force is changed in
  magnitude or - a Force from another direction is
  applied

12
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

13
ACCELERATIONNewtons 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

14
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

15
Pushing outward to get sufficient inwardF
centripetal to stay on the desired curved path