Would you like a hands on tool for teaching students about buoyancy? This small 2in x 3in x 2in boat will help introduce the concept and prove the buoyancy equation. Play around with different infill percentages and see how many pennies you can add to the boat before it sinks! You can easily calculate the theoretical number of pennies it will be able to hold with the following steps:
For my print I used a 5% infill.
F_b=(62.4 pcf)(2in3in2in)/?12?^3 ft
W_ABS=0.086 lbs (using a scale after printing)
W_pennies=0.433 lbs-0.086 lbs
N_pennies=(0.347 lbs)/(0.0055 lbs/penny)
My actual boat held 66 pennies before sinking (the surface tension of water and slight variability in penny weight accounted for the extra 3 pennies.)
You can also work backwards to calculate the mass/weight of the boat based on the number of pennies it held and compare it to the measured mass/weight using a scale.
This is a very accurate and direct application of buoyancy.