Chapter 3 Concepts

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Chapter 3 Concepts
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Mass

• Mass- the amount of matter in an object
• Units Kg, or Slugs

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Inertia

• Inertia- the resistance to a change in motion.
• The tendency to remain still if already still
• The tendency to remain in motion if already in
  motion
  

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Kinematics

• Measure of movement using
• Displacement
• Velocity
• Acceleration
• Angles

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Kinetics

• Measure of the outcomes of movement using forces

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Static

• Non-moving situations
• Forces are balanced
• Example
• Friction pushing force and resistance force are
  equal

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Dynamic

• Moving situation
• Forces are unbalanced so movement results

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Qualitative

• Analysis of movement using observation and words
  to describe the movement

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Quantitative

• Analysis of movement using discreet analysis and
  numbers to describe the moment.

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Units of Measure-

• See Table 3.1 pg 70

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Planes of motions

• Transverse plane
• Longitudinal axis
• Example twisting motion
• Sagittal plane
• Mediolateral axis
• Walking, somersaulting
• Frontal plane
• Antero-posterior axis
• Cartwheel, jumping jacks

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Definition of contractions

• Concentric
• Isometric
• Eccentric

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Types of contractions

• Concentric - muscle is shortening as it
  contracts.
  
• External force is less than muscle contraction
  force.
  
• Isometric- muscle stays the same length as it
  contracts. External force is equal to muscle
  force.
  
• Eccentric- muscle stretches as it contracts.
• External force is greater than muscle force.

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FORCE

• Force-
• mass acceleration
• mass gravity

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WEIGHT

• Weight mass gravity
• Units Newtons (N), Lbs
• Weight is a Vector because gravity has a
  direction towards the center of the earth.
  
• What is the difference between mass and weight?

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Center of Gravity

• Center of Gravity-
• The point about which an objects mass is
  distributed.
  
• Can an object have a center of gravity that is
  outside of itself?
  

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Pressure

• Pressure weight/ area
• The greater the area the less force is applied
  over any particular portion of the area.
  
• 100 lbs/ 1 in2 100 psi or lbs/in2
• 100 lbs/25 in2 25 psi or lbs/in2
• What is the difference between stepping on grass
  on high heels versus tennis shoes?
  

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Volume

• Volume lengthwidthheight
• Units m3

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Density

• Density weight/volume
• Flotation
• Whether something floats or sinks depends on
  whether the object trying to float is more or
  less dense than the substance it is floating in.
  
• Question Why might the same person float in salt
  water ( the ocean) but not in fresh water?
  

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TORQUE

• Torque Force moment arm
• Moment arm the perpendicular distance from the
  axis of rotation to the point of force
  application.
  
• Units ft-lbs, N-m
• What two methods can be used to increase Torque?

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Impulse

• Impulse Force time
• Units N-s, Lb-s
• Impulse change in momentum
• Force (mv2-mv1)/t
• If the time of impact increases then the force of
  impact decreases
  
• Implications for sports equipment
• Safety nets
• Padding
• Landing pits

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Position / Displacement

• Position (P) - the location of particle (body
  landmark, body c.g.) in space, measured with
  respect to a fixed reference system. (Position is
  a vector).
• Displacement (D) - the change in position of a
  particle (over a specified time interval).
  
  
• D Pfinal - Pinitial).
• Distance - the linear length covered over a
  specified time period. (Distance is a scalar).

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Velocity

• Velocity (V) - the rate of change of position of
  a particle.
  
• average V (Pfinal - Pinitial) / time
• average V D / time
• instantaneous V D / time (where time is
  extremely short).
  
• Units of velocity - feet per second (ft/sec),
  meters per second (m/sec), miles per hour
  (mi/hr).
  

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Acceleration

• Acceleration (A) - the rate of change of velocity
  of a particle.
  
• average A (Vfinal - Vinitial) / time
• instantaneous A (Vfinal - Vinitial) / time
  (where time is very short).
  
• Units of acceleration - meters per second per
  second (m/s2), feet per second per second
  (ft/s2)