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SIMPLE HARMONIC MOTION:PENDULUMS Unit =
21 Dr. John P, Cise, Professor =
of
Physics, Austin Com. College, 1212 Rio Grande St,
Austin Tx. 78701=
jpcise@austincc.edu & New York Times
December 19,2007 by Sar=
a Rimer
_________________________________________________=
_____________________________
At 71, Physics Professor Is a Web Star
Published: December 1=
9,
2007
CAMBRIDGE,
Mass. — Walter H. G. Lewin, 71, a physics professor, has long had a c=
ult
following at M.I=
.T. And he has now
emerged as an international Internet guru, thanks to the global classroom t=
he
institute created to spread knowledge through cyberspace.
<=
span
style=3D'font-size:5.0pt;font-family:"Arial","sans-serif";mso-fareast-font-=
family:
"Times New Roman";color:#909090'>Courtesy Markos Hankin and M.I.T.
Professor Lewin demonstrates physics of pendulums.
=
a>Professor Lewin’s videotaped physics lectu=
res,
free online on the OpenCourseWare of the Massachusetts Institute of Technol=
ogy,
have won him devotees across the country and beyond who stuff his e-mail in=
-box
with praise. In his lectures at ocw.mit.edu, Professor Le=
win beats
a student with cat fur to demonstrate electrostatics=
. Wearing shorts, sandals with socks and a pith =
helmet
— nerd safari garb — he fires a cannon loaded with a golf ball =
at a
stuffed monkey wearing a bulletproof vest to demonstrate the trajectories of objects in free f=
all. =
He rides
a fire-extinguisher-propelled tricycle across his classroom to show how a rocket lifts off. =
He was
No. 1 on the most downloaded list at iTunes U for a while, but that lineup
constantly evolves. M.I.T. re=
cently
expanded its online classes by opening a site aimed at high school students=
and
teachers. Judging from his fan e-mail, Professor Lewin, who is among those
featured on the new site, appeals to students of all ages. Some of his correspondents compare=
him
to Richard Feynman, the free-spirited, bongo-playing Nobel laureate who
popularized physics through his books, lectures and television appearances.=
With
his wiry grayish-brown hair, his tortoiseshell glasses and his intensity,
Professor Lewin is the iconic brilliant scientist. But like Julia Child, he=
is
at once larger than life and totally accessible. “We have here the mo=
ther
of all pendulums!” he declares, hoisting his 6-foot-2, 170-pound self=
on
a 30-pound steel ball attached to a pendulum hanging from the ceiling=
. He swings across the stage, holding himself ne=
arly
horizontal as his hair blows in the breeze he created. The point: that a pe=
riod
of a pendulum is independent of the mass — the steel ball, plus one p=
rofessor
— hanging from it. Professor Lewin revels in his fan mail and in the =
idea
that he is spreading the love of physics. “Teaching is my life,”=
; he
said. The professor, who is f=
rom
the Netherlands, said that teaching a required course in introductory physi=
cs
to M.I.T. students made him realize “that what really counts is to ma=
ke
them love physics, to make them love science.” He said he spent 25 ho=
urs
preparing each new lecture, choreographing every detail and stripping out e=
very
extra sentence. “Clarit=
y is
the word,” he said. Fun=
also
matters. In another lecture on pendulums, he stands back against the wall, holding a ste=
el
ball at the end of a pendulum just beneath his chin. He has just demonstrat=
ed
how potential energy turns into kinetic energy by sending the ball flying
across the stage, shattering a pane of glass he had bolted to the wall. Now=
he
will demonstrate the conservation of energy. “I am such a strong believer =
in the
conservation of energy that I am willing to risk my life for it,” he
says. “If I am wrong, then this will be my last lecture.” He closes his eyes, and releases the
ball. It flies back and forth, stopping just short of his chin. “Physics works!” Profes=
sor
Lewin shouts. “And I’m still alive!” “Professor Lew=
in
was correct,” Mr. Boigon wrote in an e-mail message to a reporter.
“He made me SEE ... and it has changed my life for the better!!”=
;“I
had never taken a course in physics, or calculus, or differential
equations,” he wrote to Professor Lewin. “Now I have done all t=
hat
in order to be able to follow your lectures. I knew the name Isaac Newton, but nothing about Newtonian Mechanics. I had h=
eard
of the likes of Einstein, Galileo.” But, he added that he
“didn’t have a clue on earth as to what they were all about.=
221;
“I walk down the street
analyzing the force of a boy on skateboard or the recoil of a carpenter usi=
ng a
nail gun,” he wrote. “Thank you with all my heart.”
Question: (a) The human pendulum above is connec=
ted to
a rope 32 feet long. Find his period? (b) Find the frequency?(c) If he gain=
ed
40 pounds what effect would this weight gain have on the period and frequen=
cy?
Answer: (a) 6.28 s (b) 0.16 cycles/s (c) __________________________.