Entry #7 - Passive Blood Stains

This. Was. Wonderful.

ABSOLUTELY WONDERFUL.

This was like the most physics part in CSI so far, and it was so interesting! After I learnt about the factors affecting blood stains - a) volumes, b) height of impact, c) force, d) density of blood, e) surface which the blood hit - I really went to observe the water droplets around us.

Firstly, the raindrops that hit the window retained a mostly spherical shape, because it wasn't absorbed by the window. You could also tell the direction of the raindrops, and it was pretty cool. Didn't realise it before.

Today, we looked at the difference in blood stains with varying heights and varying angles (we also did a crime scene but I won't tell you what happened!). AND THE DOCUMENTATION (very very important please don't forget about it!):

I have a feeling this will be a very unhappy neck-cranking experience for you readres. Fortunately, I, as the blogger, have the actual hard copy. Hehe.

Generally, there were more splatters as the height increased - 10cm stayed a nice circle, while 150cm had weird red droplet flying all ove the place. 10cm was also extremely concentrated, while 150cm was quite pale in comparison. Our results:

Vertical distance - Ave. diameter of blood stain

10.0cm - 15mm

30.0cm - 19mm

60cm - 23mm

100cm - 24mm

150 cm - 26mm

I think halfway we had to adjust the dropper, so the ave. diameter changed in pattern. However, you can see that the concentration of "blood" changed with the varying heights; 150cm had a larger diameter, thus, less concentration.



This is actually kind of common sense; the greater the angle, the narrower and longer the "blood" stain is. I'm actually not sure as to why it happens (it just does!), but I think that that's because, with a greater angle, only a small part hits the paper initially, and gets absorbed. The rest just slides down. Also, there's the direction - think raindrops on car windows. You don't see them go splat on your window, you see them go splaaaaat on your window. It's just like little clear tadpoles, with a large bottle and a small tail. See P70, it's a good indication of what I'm trying to talk about.

Angle of elevation - ave. length, ave. width = i
10 - 17.5mm, 15.5mm = 62.3 (to 1 d.p.)
40 - 20.5mm., 16mm = 51.3 (to 1 d.p.)
70 - 29mm, 10.5mm = 21.2 (to 1 d.p.)

Ok, I think there was an error with 10 and 40, but a good scientist always records down everything! :)