biomechanics week 3 angular kinematics

kinematics

the study of motion

angular kinematics

the study of angular motion

measuring angles

1. an angle is created between 2 lines

2. the point at which these 2 lines meet is the centre of a rotation joint

units of measurement ( angular measurement)

1. degrees

2. radians (rad) 1 rad = 57.3 degrees

3. Revolutions (rev) 1 rev = 360 degrees

conversions

1. converting radians into degrees: multiple by 180 and divide by pi

2. converting degrees into radians: multiply by pi and divide by 180

3. concerting degrees into revolutions: divide by 360

determining direction in angular kinematics

1. clockwise and anti clockwise

2. an anticlockwise rotation is a positive direction of movement

3. a clockwise rotation is a negative direction of movement

types of angles

absolute angle, an absolute is measured from an external frame of reference ( this can be a horizontal line measured from the centre of rotation or horizontal line)

Relative Angles

1. a relative angle is formed between two limb segments

2. a relative angle can be defined as degrees of flexion or most commonly as the angle formed at the centre of rotation (joint centre)

calculating displacement

the angle between the final position and the initial position

angular velocity

angular displacement is the change in angular displacement per unit time:

1. change in angular position divided by change in time

2. can be measure in degrees or rads

angular acceleration

angular accelaration is the change in angular velocity per unit time.

1. change in angular velocity divided by time or more simple speed divided by time

angular position and displacement

1. angular displacement defines the change in angular position

2. angular displacement is a vector (a vector has magnitude and direction)

angular displacement

= final position - initial position

angular velocity

angular displacement divided by change in time (seconds)

angular acceleration

= change in angular velocity divided by change in time (seconds)