What is Kinematics?

Kinematics is the study of motion, disregarding the forces that cause the motion.

     In order to define the motion of a body (i.e. the deformation and flow of a solid or fluid body under external loading), a continuum can be broken down into multiple "particles" and the relative change of position of each particle is monitored (see Figure).

Figure. The kinematic quantities of a classical particle: mass (m), position (r), velocity (v), acceleration (a). Image adapted from Wikipedia.

What is Deformation and Flow?

Materials (or continua) are generally classified as solids or fluids. Their main difference is that when subjected to external loading:

• a solid body will undergo time-independent deformation, and
• a fluid body will flow as a function of time.

     Materials that have both fluids and solids characteristics also exist. These include shear thickening materials such as custard (see Video), shear thinning materials such as blood, and other materials with time-dependent "visco" characteristics such as elastomers.

Video. The shear thickening effect of corn starch mixed with water.