Image modelling is a recent technique in physics education that includes digital tools for image
treatment and analysis, such as digital stroboscopic photography (DSP) and video analysis software.
It is commonly used to analyse the motion of objects. In this work we show how to determine the
position of the centre of mass (CM) of objects with either isotropic or anisotropic mass density, by
video analyses as a video based experimental activity (VBEA). Strobe imaging is also presented in an
educational view, helping students to visualize the complex motion of a rigid body with
heterogeneous structure. As an example, we present a hammer tossed with translation and rotation.
The technique shown here is valid for almost any kind of objects and it is very useful to work with
the concept of CM.