This screencast, we see how the shape of a stain defines the angle of impact. In general terms the more circular the stain, the more perpendicular will be the angle at which it struck the surface. The more elliptical the shape of the stain, the more acute the angle will be. With practice and experience, the analyst can recognize the general angle of impact based solely on the shape of the stain.

Stain Measurement & Calculating Angles of Impact (Screencast)

In this learning object the student will learn how to measure a stain and calculate angles of impact. Determining the angle of impact for bloodstains takes advantage of the trigonometric functions (Sine function).

A mathematical relationship exists between the width and length of an elliptical bloodstain which allows for the calculation of the angle of the impact for the original spherical drop of blood.

Given well formed stains we can accurately measure the width and length by simply dividing the stain along it’s major and minor axis. The opposite halves would be generally equal to each other which aids in establishing the impact angle.

In this screencast, the student will learn that regardless of the surface onto which a blood droplet is falling, the angle or velocity at which it does so, or the volume of the droplet, there are four distinct phases involved in the reaction of a moving droplet with impact against a surface.

The learner will understand how to view an object for interpretation in the standard orthographic format and then accurately sketch three orthographic views using 3rd angle projection.

Learners read about the vector diagram for a parallel RC circuit. This animated lesson presents information on current flow through each branch, total current, and phase angle.

Learners explore the use of complex numbers through a series AC circuit analysis problem. The steps are compared to the graphical method of finding circuit impedance and the phase angle.

Basic Types of Dimensioning Used in Engineering Drawings

Learners examine the basic types of dimensioning including unidirectional and aligned systems, and linear, aligned, angled, arrowless, chain, datum, chart, tabular, radius, diameter, typical, and reference dimensions.