Steel Rules Types and Usage
By Kelly Curran
In this learning activity you'll review steel rule measurement.
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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.