The Science of Blood Spatter

Spatter Definition What is impact spatter? A blood stain produced when an object makes forceful contact with a source of blood, projecting blood outward from the source.

Why do we care? Why is impact spatter important? What information can we find out using impact spatter patterns?

Why do blood spatters look different?

Dropping blood from different heights Predict the impact spatter pattern from high and low heights. Observations? Why? Why are the shapes uniform diameter? Why are there smaller droplets on the outside? (Satellite spatter) Net p=0

Airtrack Demo Predict what will happen: What observations did you make? Uneven masses? Momentum = p = mv

Spatter at different velocities What if we keep the spatter at the same height, but vary the speed? Predict what a blood droplet will look like if dropped from the same height if: Vforward = 0 (at rest) Vforward = walking Vforward = running Be ready to explain your predictions. . .

Spatter at different velocities For Vforward = 0 (at rest), draw the path of a single droplet (side view) For Vforward = walking, draw the path of a single droplet For Vforward = running, draw the path of a single droplet

Angle of Impact 𝝦

Spatter shape and Angle of Impact Demo: water balloon Predict how the angle of impact will affect the length of the spatter. Predict how the angle of impact will affect the width of the spatter.

Angle of Impact Predict the angle of incidence for each of these drops from highest angle to lowest angle.

And now for Prelab! Read the Lab: Dropped at the Scene On a piece of paper record variables answer questions graph on graph paper

Angle of Impact