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Chapter 3 Concepts

Chapter 3 Concepts. Mass. Mass- the amount of matter in an object Units: Kg, or Slugs. 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. Kinematics. Measure of movement using:

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Chapter 3 Concepts

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  1. Chapter 3 Concepts

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

  3. 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

  4. Kinematics • Measure of movement using: • Displacement • Velocity • Acceleration • Angles

  5. Kinetics • Measure of the outcomes of movement using forces

  6. Static • Non-moving situations • Forces are balanced • Example: • Friction pushing force and resistance force are equal

  7. Dynamic • Moving situation • Forces are unbalanced so movement results

  8. Qualitative • Analysis of movement using observation and words to describe the movement

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

  10. Units of Measure- • See Table 3.1 pg 70

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

  12. Definition of contractions • Concentric • Isometric • Eccentric

  13. 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.

  14. FORCE • Force- • = mass * acceleration • = mass * gravity

  15. 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?

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

  17. 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?

  18. Volume • Volume = length*width*height • Units: m3

  19. 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?

  20. 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?

  21. 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

  22. 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).

  23. 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).

  24. 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)

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