Kinematics Flashcards
(24 cards)
How many degrees are there in 1 radian?
57.3
What is angular distance?
The length on the angular path
What is angular displacement?
The difference between the initial and final positions
What is the equation for angular speed?
Angular speed = Angular distance / Time
What is the equation for angular velocity?
Angular velocity = Change in angular position / Change in time
What is the equation for angular acceleration?
Angular acceleration = Change in angular velocity / Change in time
What is a relative angle?
Angle between two segments
What is an absolute angle?
An angle defined relative to a line in space
What are the two methods for calculating relative angles from given co-ordinates?
Cosine rule
Right angled triangles and trig
What is an angular convention?
The set of rules you follow when measuring a given angle
What are the phases of ground contact and what is happening to the knee and ankle at these positions?
Footstrike - Knee flexed, ankle neutral
Initial support - Cushioning flexion of knee, small plantarflexion of ankle
Midstance - Peak flexion of knee, peak dorsiflexion of ankle
Toe-off - Knee extension, ankle plantar flexion
Swing phase - Flexion followed by extension of the knee, ankle from plantar flexion to dorsiflexion
What are the typical joint angular velocities for the ankle?
Milliron and Cavanagh (1990) 6.5 r/s
Dixon, Collop and Batt (2000) 8.1 r/s
What are the typical joint angular velocities for the knee?
Milliron and Cavanagh (1990) 9.5 r/s
Ferber, Davis and Williams III (2003) 8.9 r/s
According to Dixon and Kerwin (1999) what were the effects of a heel lift in running?
Reduced ankle dorsiflexion
Reduced Achilles tendon strain
What is the difference in clubhead velocity between amateur and professional golfers?
Professional golfers have a plateau in their clubhead velocity at the point of impact which means there is a larger margin for error during ball strike to still achieve the desired clubhead velocity.
Give some examples of analysis software.
Codamotion
Kinovea
Maxtraq
Hudl
Give a qualitative analysis of the tennis serve.
Lower body flexion then extension (ankle then knee).
Upward movement begins with GRF
Trunk rotation
Arm flexion/extension (Shoulder, elbow, wrist).
Ball strike
Where does the force in the kinematic chain come from?
Force produced by GRF or muscles
Often GRF triggers the system
Explain the principles of the kinematic chain.
Co-ordinated activation of segments
Each segment produces force and acts as a stabilising structure for the next segment
There is a proximal-distal timing of peak joint flexion and velocity
What may happen to the kinematic chain if segmental dropout occurs?
If a segment fails to execute other segments must compensate.
This may increase the risk of injury and causes performance to drop.
What were the findings from Dorge (2002) on right vs left foot kicking?
Foot velocity was influenced by knee linear velocity and shank angular velocity
There was faster ball velocity from the dominant foot
Both legs had a similar knee velocity
What is the equation that describes the relationship between linear and angular velocity?
Tangental velocity = Radius x Angular velocity
Give sporting examples where you generate greater angular velocity to increase linear velocity.
Discus
Hammer throw
High bar dismount
Cricket - Bowling
Give examples of sports where you can increase the radius of rotation to increase linear velocity.
Hammer throw
Golf
