Laura Does Science Homework

Hypothesis: Laura weighs a lot less than I do, but my feet are so much bigger that the pressure evens out

Method:

Trace our feet on paper

Cut feet out and take a photo of both together (to ensure consistent scaling)

Make the background black and the feet white in a photo editor

Save the feet separately as PNG

Calculate the number of white pixels using ImageMagick:

for x in *_foot.png; do echo -n "$x    "; convert $x -fuzz 4% -fill White -opaque White -fuzz 0 -fill Black +opaque White -precision 15 -format %[fx:int(mean*w*h+0.5)] info:; echo ``; done

Results:

daddy_foot.png    3337623 laura_foot.png    2031393

Laura pressure: 14.3 lbs/megapixel (2 feet)

Dad pressure: 35.2 lbs/megapixel (2 feet)

Hypothesis was way, way wrong

Surface Tension Boat Race

Cut a little boat shape out of plastic

Put a small slit at the stern

Gently place the boat into a dish of water

Drop a tiny amount of dish detergent at the deepest point of the ship (closest to the bow)

Watch the boat jet across the water!

What’s going on here is that the detergent is breaking up the surface tension of the water behind the boat, pushing the boat forward. I don’t know if this is because of the intense power of Dawn or just the way this goes, but it didn’t take long before all the surface tension in the water was gone. At that point the boats wouldn’t float, let alone glide.

March, 2015 - Vortex Cannon

Parts: Can Bandz to hold a trash bag over a plastic trashcan. The large exit hole in the trashcan was made with great violence and inappropriate tools. The knob made of Sculpey by Laura and me, “drilled” with a chopstick, and baked in the oven. A Can Band was threaded through those holes and into two holes we drilled in the trashcan, secured on the outside with paperclips. 

The vortex thrown was pretty tight so the aim was touchy, but we were able to blow out a candle at distance of 15′ or so without trouble. The first time we did it there was much dancing and celebration!

March 29, 2015 - Spaghetti Structures

Time for a little more measurement stuff. We hung some weights on some strings and saw what happened. This was a bit impromptu, so I didn’t get the kinds of strings I wanted, but whatever. We graphed* the cotton’s stress vs. strain and took a guess about where 3.1Kg would end up. It was 112 on the dot! We danced in celebration.

Electroplating! Coins were dumped in vinegar and attached to a battery. We learned that the iron from the paperclip on the anode can be a problem, so next time we’ll be sure to keep that guy out of the vinegar. Also, the battery was a 1.2V rechargeable. We may have done better with a 1.5V source like an alkaline. Also, I ran with two pennies (pre-1982) to try to get some free copper in the vinegar. The solution never turned color, possibly again because of the poisoning from the iron.

March 1st, 2015: waves. We used the keyboard and a spectrum analyzer to look at sound waves. We started with an A tuning fork, moved on to the piano and the zither. This spectrum analyzer is also how I tune the zither. 

February 10-11, 2015: litmus paper

We made litmus paper by boiling cabbage one night. The next night we measured stuff we had around the house: Water, cream of tartar, baking soda, baking powder, bleach, ammonia, vinegar, etc. We used an ice cube tray to keep things separate. 

Dec. 11, 2014: paper chromatography with food coloring

Feb 19, 2015: density by water displacement.

We did this one in the tub. Eureka!

Feb. 21, 2015: pendulums

We hung this old doorknob (425g, 15oz) from a string and measured how many swings we got in 10 seconds as we changed the length of the string. We also recreated the Neil deGrasse Tyson “boop” by touching the doorknob to our noses and letting it go.