homework 07 – ALIBHAI, ZAHID
1
Latest unpenalized work: Mar 5 2007 Monday
04:00 (after this date you can not make a
perfect score). Work cutoF: Mar 7 2007, 4:00
am.
Question 1
part 1 of 1
10 points
In introductory physics laboratories, a typ
ical Cavendish balance for measuring the
gravitational constant
G
uses lead spheres of
masses 2
.
34 kg and 13
.
9 g whose centers are
separated by 5
.
54 cm.
Calculate the gravitational force between
these spheres, treating each as a point mass
located at the center of the sphere. Use
G
=
6
.
67259
×
10

11
N m
2
/
kg
2
.
Answer in units of N.
Question 2
part 1 of 1
10 points
Given:
G
= 6
.
673
×
10

11
N
·
m
2
kg
2
Mars has a mass of about 6
.
97
×
10
23
kg,
and its moon Phobos has a mass of about
9
.
44
×
10
15
kg.
If the magnitude of the gravitational force
between the two bodies is 4.69
×
10
15
N, how
far apart are Mars and Phobos?
Answer in units of m.
Question 3
part 1 of 1
10 points
Planet X has three times the diameter and
six times the mass of the earth.
What is the ratio of gravitational accelera
tion at the surface of planet X to the gravita
tional acceleration at the surface of the Earth,
g
x
g
e
?
1.
g
x
g
e
=
5
49
2.
g
x
g
e
=
2
3
3.
g
x
g
e
=
9
64
4.
g
x
g
e
=
9
25
5.
g
x
g
e
=
2
25
6.
g
x
g
e
=
6
49
7.
g
x
g
e
=
7
16
8.
g
x
g
e
=
1
32
9.
g
x
g
e
=
5
16
10.
g
x
g
e
=
2
81
Question 4
part 1 of 1
10 points
Two iron spheres, of mass
m
and 2
m
,
respectively, and equally spaced points “
r
apart” are shown in the ±gure.
A
m
B
C
D
2
m
E
r
r
r
r
r
r
At which location would the net gravita
tional force on an object due to these two
spheres be a maximum?
1.
E
2.
C
3.
A
4.
D
5.
B
Question 5
part 1 of 2
10 points
Given:
G
= 6
.
672
×
10

11
N m
2
/
kg
2
.
The planet Mars requires 1
.
73 years to orbit
the sun, which has a mass of 2
×
10
30
kg, in
an almost circular trajectory.
Calculate the radius of the orbit of Mars as
it circles the sun.
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2
Answer in units of m.
Question 6
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 Mass, Work

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