Floating Lab

Activity 1

Materials : 1 square of aluminum foil 15 cm x 15 cm
50 pennies

1) You're going to make a boat that holds as many pennies as possible with the piece of aluminum foil. What "tradeoffs" will you have to make as you think about a design ?

2) Make what you think will be the best design for holding pennies for an aluminum foil boat that floats. Draw your design, labeling all dimensions.

3) Load it with pennies, one at a time, counting carefully. How many pennies did your boat hold ?

4) What was the specific reason why your boat failed ? Make a failure analysis.

5) Get an new piece of 15 x 15 cm piece of foil. Based on the behaviour of your first boat, redesign and manufacture a new improved boat. Draw and label it. Test it. How many pennies did it hold ?

5a) Weigh one penny, and weigh the aluminum foil.

Weight of one penny ________ g
Weight of total pennies successfully floated ____ g
Weight of foil ________ g

Calculate the floated weight (all pennies + boat) / weight of boat = _______

You know that CONCRETE (?!?%^) boat in Aptos ? How does that work ?

Activity 2

6) Get a piece of foil only half as long on each side. How long is that ?

7) Based on whichever design worked better from activity 1 above, make an exact replica of your most successful boat. Draw and label the dimensions of your small boat.

8) Make a PREDICTION : The big boat held _______ pennies before sinking, so this small boat will probably hold _______ pennies.

9) Test your prediction. The small boat actually held _______ pennies. Was your prediction accurate ?

10) Using the method from 5a above, calculate the ratio of
floated weight /boat weight. _____________

HOW DOES THIS RATIO COMPARE TO THE RATIO YOU OBTAINED FROM THE BIGGER BOAT ?

Questions

a) Why does something float ?

b) Why does something sink ?

c) What parameter changed when your boat went from from floating to sinking ? Warning: this answer requires thinking ! The answer " It weighed more" is NOT enough !

d) Who said "EUREKA!" ? Why ?

e) What is bouyancy ? What is density ? What is displacement ?

f) Why does the Goodyear Blimp stay up in the air ?

g) In Activity 2, if you made a prediction based on dividing the # of pennies in half, you probably didn't get too close. Why ?

h) So how many pennies would an aluminum foil boat 15 km square hold, based on your design ?

i) What new kinds of failure modes would you begin to see in an aluminum foil boat this large ?

j) How does that relate to those movies where giant insects attack New York ?

k) Because, as things get large, they have two geometric properties that grow, but not an equal rate. What are these qualities ?

l) So if you build anything using a model to plan, you had better be very ___________.