Biomechanics Chapter 6: Angular Kinematics

Relative angular position refers to the orientation of an object relative to

a nonfixed reference line or plane.

When an object rotates, it undergoes

an angular displacement.

Angular kinematics is concerned with the description of

angular motion.

The angular movements of limbs around joints are

described with terminology developed by anatomists using the anatomical position of the body as a reference.

The definitions of angular displacement, angular velocity, and angular acceleration are similar to those for their

linear counterparts.

The linear displacement and distance traveled by a point on a rotating object are directly proportional to the

radius of rotation.

Joint angles are relative, whereas limb positions may be

relative or absolute.

The three principal anatomical planes are

sagittal, frontal, and transverse

Lengthening the radius while maintaining the angular velocity is an important principle in a variety of

striking skills.

To define the angular displacement, what must be known?

the axis and plane of rotation

Centripetal acceleration (also called radial acceleration) of an object rotating in a circular path is

the component of linear acceleration directed toward the axis of rotation.

Centripetal force is

the force exerted on the rotating object to cause the centripetal acceleration.

Absolute angular position refers to

the orientation of an object relative to a fixed reference line or plane, such as horizontal or vertical.

Tangential linear acceleration is equal to

the product of angular acceleration times the radius of rotation.

The linear distance traveled equals

the product of the angular displacement measured in radians times the radius of rotation.

The tangential linear velocity is equal to

the product of the angular velocity times the radius of rotation.

Tangential linear velocity and acceleration of a point on a rotating object are directly proportional to

the radius as well.

The direction of the angular displacement (and all other angular motion and torque vectors) is then established using

the right-hand thumb rule.

It is directly proportional to

the square of the tangential linear velocity or the square of the angular velocity.

Their corresponding axes are

transverse, anteroposterior, and longitudinal

Angles describe the orientation of

two lines.

These planes and axes are

useful for describing movements of the limbs.