The Medical College - Page 37
Passage I (Questions 66–71)
A human centrifuge is used to test and train
pilots
and astronauts to withstand the large "g-forces"
experi-
enced during flight. The centrifuge arm length
is such
that the subject moves in a large circle of
radius 9 m.
The maximum angular velocity is 4 radians/sec.
The
subject normally faces inward toward the center
of the
circular path. ("eyeballs in").
During a test, the subject's respiratory and
metabolic
rate rise. The energy released per liter of
oxygen
consumed in human metabolism averages
about
20,000 J/L.
66.
What is the maximum linear (tangential)
speed
of the subject along the circular path at the
maxi-
mum angular velocity of 4
radians/s?
A.
18 m/sec
C.
36 m/sec
B.
25 m/sec
D.
226 m/sec
67.
A pilot of mass 82 kg (180 lbs) experiences 8
"g's"
during one test for a period of 2 minutes. What
is
centripetal force, in newtons, acting on the
pilot?
A.
16 N
C.
960 N
B.
660 N
D.
6400 N
68.
In the earth frame of reference, what
centrifugal
force acts on the pilot during the
test?
A.
The centrifugal force on the pilot is equal
and
opposite the centripetal force on the
pilot.
B.
The centrifugal force on the pilot is 1
"g"
larger than the centripetal force on the
pilot.
C.
The centripetal force on the pilot is 1
"g"
smaller than the centripetal force on the
pilot.
D.
There is no centrifugal force on the
pilot.
69.
The pilot's metabolic rate rises to 450 W
and
remains at that level during the 2 minute test
period.
What is the approximate number of liters of
oxygen
consumed by the pilot during the test
period?
A.
3 L
C.
6 L
B.
4 L
D.
10 L
70.
What force acts on the back of the pilot's
seat?
A.
0 N
C.
960 N
B.
88 N
D.
6400 N
71.
The pilot now faces outward ("eyeballs
out").
What effect does this have on the
centripetal
force acting on the pilot?
A.
The centripetal force now points
outward.
B.
The seat back now exerts an outward
force.
C.
The centripetal force is replaced by
the
centrifugal force (now supplied by
the
pilot's seat harness).
D.
The centripetal force is unchanged
(now
supplied by the pilot's seat
harness).
Passage II (Questions 72–77)
A periscope viewing system is to be used to
observe
the behavior of primates in a large
environmentally con-
trolled room on the upper floor of a large
research facil-
ity. The periscope, like those used on
submarines, is
essentially a large, folded-path, low-power
telescope
(using prisms to fold the light path). A sketch
of the pre-
liminary design appears below. Like all
Newtonian tele-
scopes, it uses a relatively long focal length
objective
lens to form a real image in front of the
eyepiece lens (of
shorter focal length). The observer looks
through the eye-
piece lens to see the final image, in the same
manner that
one would use a magnifying glass. The distance
between
PHYSICAL SCIENCES
10 PROBLEM SETS
OF 5–10 QUESTIONS EACH
15 PROBLEMS FOLLOWED
BY A SINGLE QUESTION
77 QUESTIONS
100 MINUTES
DIRECTIONS:
The following questions or incomplete
statements are in groups. Preceding each series of
questions or statements is a paragraph or a
short explanatory statement, a formula or set of
formulas, or a definition. Read the written
material and then answer the questions or com-
plete the statements. Select the ONE BEST
ANSWER for each question and indicate your
selection by marking the corresponding letter
of your choice on the Answer Form. Elim-
inate those alternatives you know to be
incorrect and then select an answer from among
the remaining alternatives. A periodic table is
provided (see p. 601). You may consult it when-
ever you wish to do so.
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