What Do I Really Need to Know About Biomechanics
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Transcript of What Do I Really Need to Know About Biomechanics
What Do I Really Need to Know About Biomechanics
The Cole’s Notes to Mr. Wardle’s abstract and somewhat disjointed
thinking (if you have had Mr Gajic as a teacher then you will be just fine)
Kinematics
• The branch of biomechanics that studies the movement with reference to the amount of time that it takes to carry out an activity
• It includes– Movement– Path of the Movement – and Time
Distance and Displacement
• Distance– The path that an object or body follows
• Displacement– The length of a straight line from start to finish
points
Speed and Velocity
• In this course the difference is not really needed for any practical applications as we are studying short distance linear movements
• Velocity is the change in position and the time it takes for it to happen
Acceleration
• Usually done as an average over a period of time
• The rate at which velocity changes• Can be easily found from D/T and V/T graphs• From Newton’s 2nd law (F=ma)
• Acceleration due to Gravity is 9.81m/s/s
Torque
• The moment of force at a perpendicular distance to a joint or point of rotation
• Ex - turning a bolt and the force on the handle (the further your hand is away from the blot the easier it is – the longer the moment arm)
• Ex – Closing a door (I think we have talked about this one enough)
Newton’s Laws
• 1st – Objects are Lazy
• 2nd – F=ma
• 3rd – Everything has an equal and opposite consequence
Linear Kinematics
• Momentum – mass X velocity
• Inertia – the reluctance of a body to change what it is doing
• Force – a pushing or pulling action that causes a change of state of movement of a body
Angular Kinematics• Movement but involving some sort of rotational
movement• Can happen with linear movement• Angular displacement is the number of degrees
(or radians, 1 radian = 57.3’) that an object moves through
• Angular velocity is the rate of change of angular displacement
• Angular acceleration is the rate of change of angular velocity
Examples of Angular Kinematics
• A skater turns at 360’ (6.28 radians) – this is her angular displacement (1 turn – it doesn’t matter how “big” she is – that would be circumference)
• If each turn takes her 1 second her angular velocity is 360’/s or 6.28r/s
• If she speeds up to double that rate in 1s her acceleration is 360’/s/s or 6.28r/s/s ending at 720’s
Angular Momentum
• Angular Momentum = Angular velocity X moment of inertia
• Is set once a body is “free” due to Law of Conservation of Motion
• Applies to skaters, divers etc– They decrease their moment of inertia (width –
bring their arms in) and in order to keep their Angular Momentum the same their Angular Velocity speeds up
D/T Graphs
• 1 – stopped (doesn’t matter where this is on the y axis)
• 2 – constant velocity• 3 - accleration
V/T
• Stopped
• Decreasing Velocity
• Increasing Velocity
• Stopped