
Joanne
Pirog
Lesson
Plan IV
Volume
and weight of a balloon filled with water. The Trebuchet project involved the
launching of water filled balloons that weighed sixteen pounds. We used *in
class 9‑inch balloons. This 9 'inches was the diameter of the balloon.
We filled it with water to its full capacity (volume). We wanted to figure out
how heavy this balloon would be by using its volume formula. The formula we
used was V = 4/3 pi r^3 Example: 9‑inch balloon, diameter = 9 in. The
radius is = 4.5 in. We used
3.14
for pi.
V = 4/3 (3.14)
(4.5)^3 V = 381.4 cu in Change
to centimeters using (2.54 cm = 1 in) V = (381.4)
(2.54cm/in)^3 V
= (381.4) (16.4) = 6250 cm^3 =
6250 grams and
6250/454 ~ l3.5pounds
Next
have students actually fill up the balloon and actually weigh them to see if
our mathematical expectations actually materialize. 
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