Ch.6 Angular Kinematics

What is Angular motion?

- all points on an object moves in circles about the axis

What is Angular kinematics?

- description of the angular motion or angular aspect of general motion

What is a plane?

- imaginary flat surface on which movement occurs or takes place

What is an axis?

- line/point about which object rotates (always perpendicular to plane)

What is the medial-lateral axis?

- axis that is perpendicular to the sagittal plane
- runs in medial to lateral direction (side-to-side)

What is the anterior-posterior axis?

- axis that is perpendicular to frontal plane

What is the longitudinal axis?

- axis that is perpendicular to the transverse plane

What needs to be specified when describing angular motions?

- plane
- axis

What is angular position?

- described using measurement of an angle from a reference position in a specific plane

What are the different direction of angular position?

- counter clockwise (+)
- clockwise (-)

What is angular distance?

- how far the point rotated around the axis
- scalar

What is angular displacement?

- how far the point rotated around its axis in a specific direction
- vector quantity

What is angular speed?

- how fast the point is rotating around the axis
- scalar quantity

What is angular velocity?

- how fast the point is rotating around the axis in a specific direction
- vector quantity

Average angular speed/velocity vs. instantaneous speed/velocity

- angular speed/velocity averaged over time vs. angular speed/velocity of a specific time point

What is angular acceleration?

- rate of change in angular velocity
- fast angular velocity is changing, greater angular acceleration

What relationship is between angular acceleration and object direction?

- when object is moving + direction, + acceleration will speed up angular motion
- when object is moving - direction, + acceleration will slow down angular motion

When is angular acceleration 0?

- object is not moving
- rotation at a constant angular velocity

What are some movements that occur on the medial-lateral axis?

- flexion
- extension
- dorsiflexion
- plantar flexion

What are some movements that occur on the anterior-posterior axis?

- abduction/adduction
- lateral flexion
- radial/ulnar deviation
- inversion/eversion
- knee valgus/varus
- elbow valgus/varus

What are some movements that occur on the longitudinal axis?

- internal/external rotation
- right/left rotation
- supination/pronation
- shoulder horizontal abduction/adduction

What is the key to success in various sports/activities?

- maximizing angular speed and angular velocity

What is the relationship between linear and angular motion?

- angular motion of an object results in linear motion of the points on the object

What is tangential direction?

- a point/object that moves linearly in a direction tangent (coming off of) to the rotating path

What is tangential displacement?

- linear displacement in the tangential direction

What can create a greater tangential displacement?

- greater angular displacement
- longer radius of rotation

What is tangential velocity?

- linear velocity in the tangential direction

What can create a greater tangential velocity?

- greater angular velocity
- longer radius of rotation

What is tangential acceleration?

- linear acceleration in the tangential direction
- rate of change in tangential velocity

What can create a greater tangential acceleration?

- greater angular acceleration
- longer radius of rotation

Relationship of limb length and angular motion

- usually a person with longer limbs will have an advantage as they can create more force

What is radial acceleration?

- change in direction of linear velocity results in acceleration of the mass towards the center of rotation
- represents rate of change in direction of tangential velocity

What is radial acceleration scenario 1?

- occurs when the object is going through an angular motion
- ex) baseball swing, hammer thrower

What will increase radial acceleration scenario 1?

- increasing angular velocity
- increasing distance between axis and the point

What is radial acceleration scenario 2?

- occurs when object is turning a corner moving linearly along a curved path (object must stay in circular path)
- ex) speed skater turning a corner or trach athletes turning a corner

What will increase radial acceleration scenario 2?

- increasing tangential velocity
- decreasing distance between axis and the point

What is centripetal force?

- produces radial acceleration
- force pulling object towards center of rotation

What will increase centripetal force?

- increasing radial acceleration
- increasing object mass