PHY 317K
HOMEWORK # 3
DUE on October 14, 2009 by 8:00pm
Instructions:
Use a UT ANSWER SHEET to mark answers. Provide your
NAME
(last, first),
UTEID
, and
UNIQUE NUMBER
of the course. Sign and date it. The answer sheets must be
placed in the
317K box
located outside PAI 2.48.
Late homework will not be graded
.
Answer the following 76 questions:
1. The approximate value of
g
at an altitude above Earth equal to one Earth diameter is:
A) 9.8 m/s
2
B) 4.9 m/s
2
C) 2.5 m/s
2
D) 1.9 m/s
2
E) 1.1 m/s
2
2. Four particles, each with mass
m,
are arranged symmetrically about the origin on the
x
axis. A fifth particle, with mass
M
, is on the
y
axis. The direction of the gravitational
force on
M
is:
3. Three particles, two with mass
m
and one mass
M
, might be arranged in any of the four
configurations known below. Rank the configurations according to the magnitude of the
net gravitational force on
M
, least to greatest.
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4. Venus has a mass of about 0.0558 times the mass of Earth and a diameter of about 0.381
times the diameter of Earth.
The acceleration of a body falling near the surface of
Venus is about:
5. To measure the mass of a planet with the same radius as Earth, an astronaut drops an
object from rest (relative to the planet) from an altitude of one radius above the surface.
When the object hits the surface, its speed is 4 times what it would be if the same
experiment were carried out for Earth, ignoring any drag forces from the planets'
atmospheres. In units of Earth masses, the mass of the planet is:
A) 2
B) 4
C) 8
D) 16
E) 32
6. The mass of a hypothetical planet is 1/100 that of Earth and its radius is 1/4 that of
Earth. If a person weighs 600 N on Earth, what would he weigh on this planet?
7. An object is dropped from an altitude of one Earth radius above Earth's surface. If
M
is
the mass of Earth and
R
is its radius the speed of the object just before it hits Earth is
given by:
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