The
Physics of Falling Pumpkins and Basketballs
If
you drop a basketball and a medium-sized pumpkin from the
roof of McConnell Hall, which will hit the ground first?
That, in simplified form, is
similar to a question that 400 years ago spurred one of the
most famous scientific experiments in history, by Galileo
Galilei, who dropped objects from the leaning Tower of Pisa
to test their rate of fall.
Click on image to view a of the Galileo
experiment.
Laura Romanowski ’14
(on left) and Blaire Thomson ’14
prepare to drop pumpkins and basketballs. |
Last week, first-year students,
Blaire Thomson, a STRIDE scholar, and Laura Romanowski, an
AEMES scholar, fashioned their own version of the famous
physicist’s experiment for a research project under the supervision
of Joyce Fortune, a lecturer and lab instructor in physics.
The students built a “launching” contraption
in which two objects can be placed on an overhanging platform
affixed to the roof. At the pull of a string, the platform
slides out and the objects fall simultaneously toward the
ground. () A catch tarp
was spread on the McConnell courtyard brick floor to contain
the splatter.
Two high-speed video cameras
captured the action, one parked across the courtyard shooting
through a window from inside a Burton Hall second-floor room,
the other on the ground a few feet from the drop cloth.
The
experiment was part of an ongoing project conducted by Fortune
to gather high-speed video footage of motion happening in
very small time scales, she explained, to show to students
in her introductory physics classes.
“I want them to know that physics is based on observation, as all science is,” she
said, “even if some things are hard to observe.” By shooting high-speed video,
Fortune can slow down fast-paced events, such as two objects falling and hitting
the ground, for close observation, she said.
Thomson and Romanowski conducted
several trials, observing the pumpkins’ spectacular smash against the hard ground
while the basketballs bounced 30 feet in the air before settling.
Whoops echoed
through the courtyard with each test of the falling objects. “Those were a little
off,” the students conferred following the drops, each scribbling notes. “That
one was really close.”
Thomson and Romanowski are reviewing
the footage of their pumpkins and basketballs to observe
in slow motion what the respective objects’ drop rates can tell them—physical
statistics like velocity, acceleration, drag and volume.
Their conclusions may
support Galileo’s theory. Prior to his experiment, legend goes, Greek philosopher
Aristotle had asserted that if two objects were dropped simultaneously, the heavier
one would drop faster. Following his experiments in Pisa, however, Galileo concluded
that regardless of objects’ weight, when dropped simultaneously from an equal
distance, they will fall at the same rate. What alters their rate of fall—and
their drag in the air—is the volume and shape of the objects, not their weight.
“Galileo’s results are not in question, but if you ask nearly anyone who has
not taken physics—and quite a few who have—they will tell you what Aristotle
said: that heavier objects fall more quickly than light objects,” said Fortune. “This
is one of the most vexing misconceptions students bring to intro physics, and
I wanted a really splashy demonstration that they could remember to help make
the point.” |
