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MOMENTUM CONSERVAT=
ION Unit 12 =
span>Dr
John P. Cise, Professor of Physics,
Austin
Community College,1212 Rio Grande St., Austin Tx., 78701 jpcise@austincc.edu & New York Times , Feb 8,2009 by John
Branch
Lugers Measure Success in Degrees of Recovery
mn
U.S. luger Tony Benshoof, recovering from back woes=
, was
18th in the world men’s singles final.
LAKE PLAC=
ID, N.Y.
— It is one of luge’s quirks that, in a sport where speeds can
exceed 90 miles per hour, one of the most common and debilitating injuries
develops before the races begin. Lugers, seated on a sled, propel themselves
down the icy chute by holding handles at the start line and sometimes rocking back and forth. Th=
eir
final one-two thrust sends them backward as far as their bodies can stretch,
and then snaps them forward, onto the course.“We sh=
ove
ourselves into what we call compression, where you pretty much use your bac=
k as
a rubber band to explode out of the handles,” the American luger Tony
Benshoof said Friday, the day before the men’s singles world
championship.The men’s singles race was also Benshoof’s first r=
ace
back since surgery on Dec. 26 to repair a herniated disk in his lower back.=
“You go all the way back as far as you can, and
then you explode out,” Benshoof, 33, said. “So you’ve got the sleds that weigh
about 50 pounds, plus all the momentum going back, and really the back is t=
he
engine that fires you out of there.”Bulging or herniat=
ed
disks ultimately catch up to almost all luge racers, a result of years of
repeated abuse on their backs. “The problem is the start, where they =
go
from flexion to extension with so much torque in their back,” said Dr.
Eugene Byrne, the chief medical officer for the United States luge t=
eam.Introduction:
With no friction to speak of(ice surface)no external force is essentially
exerted to this system of sled
plus person on the sled. Thus, momentum is conserve=
d. Ques=
tion:
Find the speed V2 which the lunger must thrust hisupper
torso(back,head,arms…consider those to weight 64 lbs)backward in order
that the sled and lower body(50 lb sled + 128 lb lower body) can snap forwa=
rd at
the start at V1 =3D 15 mph? Answer: ~42 mph
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