biomechanics

• How many Newton laws of linear motion are there?

  3
• What is Newtons first law of linear motion?

  First law of inertia
• What is the law of inertia?

  Body continues in a state of rest or uniform velocity unless acted upon by an external or unbalanced force
• What is Newtons second law of linear motion?

  Second law of acceleration
• What is the law of acceleration?


  Acceleration of a body is directly proportional to the magnitude of the force produced and its governed by the direction that the force is applied
• What is the equation for force?

  mass x acceleration
• What is Newtons third law of linear motion?

  Law of action-reaction
• What is the law of action-reaction?


  For every action there is an equal and opposite reaction force
• Example of Newtons 1st law of linear motion on a footballer jumping for a header

  Footballer applies a force to the ground by contracting their leg muscles

  If the force is large enough to overcome their inertia, they will move from a stationary position to jump
• Example of Newtons 2nd law of linear motion on a footballer jumping for a header

  The mass of the footballer remains constant, so the greater the muscular force applied to the ground, (from the legs,) the faster they will accelerate upwards in their jump and the higher they will go to meet the ball in a header
• Example of Newtons 3rd law of linear motion on a footballer jumping for a header

  Footballer applies a muscular force to the ground and the ground will apply an equal and opposite force back on the player

  If the footballer applies a large force on to the ground, this will generate a large force upwards from the ground onto the player

  This will allow the footballer to jump higher and they will be more likely to meet the ball at the optimal height for a successful header
• What is the definition of a scalar quantity?


  Scalar quantities refer to measurements based on magnitude/size only
• What is magnitude?


  Size
• What are the 3 scalar quantities?

  Speed

  Distance

  Mass
• What is the definition of speed?

  Rate of change of position
• What is the equation of speed?


  Distance/time
• What are the units for speed?

  m/s
• What is the definition for distance?

  Length of the path a body moves when moving from one position to another
• What is the equation for distance?

  speed x time
• What are the units for distance?

  Metres (m)
• What is the definition of mass?


  Quantity of matter a body possesses
• What are the units for mass?

  kg
• What does a straight line on a speed graph show?

  Body is stationary because as time passes, distance does not change
• What does an upwards curve on a speed graph show?

  When the change in distance increases as time passes, the body is speeding up
• What does a linear line on a speed graph show?

  Distance increases uniformly as time passes, the Boyd is moving at a constant speed
• What does a downwards curve on a speed graph show?

  When the change in distance decreases as time passes, the body is slowing down
• What is a centre of mass?

  Point at which a body is balanced in all directions

  Point where all the mass of a body is concentrated

  Point which weight appears to act
• What happens to our centre of mass as our body moves?

  Moves
• What is stability?


  The ability of a body to resist motion and remain at rest, (remained balanced)
• What are the 4 factors affecting stability?

  Height of centre of mass

  Area of base of support

  Position of line of gravity

  Body mass
• How does the height of centre of mass affect stability?

  A lower COM increases stability
• How does the area of base of support affect stability?

  Wider base of support increases stability

  The more contact points the greater the stability
• Does the amount of contact points affect stability?

  Yes- more contact points increases support and stability
• How does the position of line of gravity affect stability?

  A body is stable when line of gravity is central over the base of support
• How does body mass affect stability?

  The greater the mass of a body, the greater the stability
• Example of how a tennis player receiving a serve will increase their stability

  Flexion at knees- lowers COM- able to respond to where the serve arrives

  Wider base stance- able to be more stable when receiving the ball

  Flexion at hip- line of gravity central over the base of support, able to change direction quickly
• Why would a rugby player need good stability and how is this achieved

  When preparing to tackle, can be more effective and able to change direction quickly

  Increases stability by: flexing knees and hip to lower COM

  Increases width of feet to widen base of support

  Increase number of contact points by ensuring both feet in contact with ground

  Positioning line of gravity directly over middle of base of support

  Larger mass increases stabile
• What will happen to rugby player if factors that impact stability are applied wrong?

  Too much mass- affect mobility and make less stable

  Base of support is too wide- tackler loses ability to change direction quick. If too narrow, player compromises stability

  Tackler shifts their position of line of gravity closer to the edge of base of support, it might help them to change direction of tackle faster

  Altering height of COM can help a player tackle more effectively
• How many lever systems are there?

  3
• How do you remember the position of the middle component of levers?

  1,2,3

  F,L,E