Buoyancy Boat for science teachers!

thingiverse

Would you like to teach students about buoyancy hands-on? This compact 2in x 3in x 2in boat is just the thing, introducing the concept while proving the buoyancy equation. Experiment with various infill percentages and see how many pennies it will hold before sinking! Calculate the theoretical number of pennies with these simple steps:\nI printed my own version using a 5% infill.\nFirst, determine F_b, the buoyant force:\nF_b=(62.4 pcf)(2in x 3in x 2in) / (?12)^3 ft\nCalculate F_b=0.433 lbs with this formula.\nNow subtract the actual weight (measured with a scale): W_ABS=0.086 lbs\nW_pennies=F_b - W_ABS, so calculate the weight of pennies:\nYou get W_pennies=0.347 lbs when you subtract 0.086 from 0.433 lbs.\nTo find N_pennies, divide W_pennies by penny weight: (0.0055 lbs/penny).\nThe answer is N_pennies=(0.347 lbs)/(0.0055 lbs/penny), which equals 63 pennies.\nMy actual boat held a surprising 66 pennies before sinking, thanks to water surface tension and minor penny weight variation for the extra 3 pennies!\nBy reversing this process, you can also calculate the boat's mass/weight from the number of pennies it held and compare it with the scale-measured mass/weight.\nThis is a direct and accurate application of buoyancy principles.