I saw the headline this weekend about students dropping a piano from a dormitory roof, I figured it was yet
another installment of the annual Piano Drop orchestrated by the Massachusetts Institute of Technology
(MIT) engineering class; it was. The Piano Drop is held on the same day as the last
day that a class can be dropped. In 1972, notorious trickster Charlie Bruno decided it would be a good idea to
take a piano to the roof of the Baker House
("Year after year, Baker is the top choice in the housing lottery") and, with great
fanfare by assembled students below, send it to its undignified musical death. According to witnesses, though,
rather than go out with a cacophony of nonharmonic percussional tones and semitones, the ceremony ended with a
single, short-lived loud thud. Still, for guys, just watching something fall from great heights and crash to the
ground is worth the trouble. Don't doubt me on this.
This year's event marks two important benchmarks, one
of which helped boost the story to the national level. 2012 is the 40th anniversary of the piano drop tradition,
and, the reason for increased coverage, it is the first time that dropped classes can be expunged from a student's
As a side note, in honor of Charlie's efforts, a new unit of measure was named after him: the
Bruno. One Bruno is "A unit of volume equal to the size of the dent in asphalt resulting from the free fall of an
upright piano. Determined to be 1158 cubic centimeters when the experiment was first performed in 1972. [MIT
Club of Boston, 1999]." According to their calculations, the piano was traveling at 43 mi/hr and contained 45000 kft·lbs of energy when it hit. This
year's event was used as an opportunity to "recalibrate" the Bruno unit.
Since most of us here are
engineers or technicians, I am providing the calculation for the velocity. I could not find the exact height of
the Baker House, but it is six stories, and a typical building story is 10 feet tall. Plus, there is about a
3-foot high safety wall on the roof. So, let us assume a height of (6 x 10)+3 = 63 feet. The equation for final
speed of a falling object with a beginning speed = zero (0) is given by:
s = sqrt (2 g h) (neglecting air
s = sqrt (2 32.2ft/s 63ft) = 63.7 ft/s = 43 mi/hr...
in agreement with the published speed.
Verification of the energy content is left as an exercise for the
MIT is no stranger to creating new units of measure. Another famous engineering student,
Oliver Smoot, was used as a "yardstick"
by fellow students to determine the length of the Massachusetts Avenue Bridge, which has been determined to be
364.4 Smoots long. Google even has the built-in converter (they do not have a Bruno unit