Rectilinear Translation motionAll parts of the object have the same speed.

Rectilinear Translation motionAll parts of the object have the same speed.

Rectilinear Centre of mass used to quantify amount of

movement

Curvilinear motion is a type of translationAll parts of the object have the same speed.

Curvilinear motion is a type of translationAll parts of the object have the same speed.

Rotation (or angular motion)Different parts of the body have different

speeds

Rotation (or angular motion)Different parts of the body have different

speeds

General Motion Consists of both translation and rotation

General Motion Use centre of mass for translation

General Motion Use angles for rotation

Angular Displacement

Angles are measured in an anticlockwise direction from the right hand horizontal (usually the positive

x axis)

Angular Displacement

Angles are measured in an anticlockwise direction from the right hand horizontal (usually the positive

x axis)

70 deg

Only absolute angles of segments measured from right hand horizontal.

These give the angle of a segment

110 deg

Relative angles are measured between segments. (ie the angle of a joint).

70 deg

60 deg

thigh = 60 degshank = 70 deg

knee = shank - thigh = 10 deg

Angles often measured as angles of flexion from the anatomical position

(ie anatomical position is assigned the value of zero).

10 deg

Note: direction of positive and negative is entirely arbitrary for relative angles.

There is no accepted convention

0 deg

-20 deg

+20 deg