Section 7.1
Planetary Motion and Gravitation
Practice Test
1.
The time it takes a comet to complete one revolution is called the _______.
a.
period
b.
orbit
c.
ellipse
d.
focus
Hint
2.
Two bowling balls each have a mass of 6.3 kg. They are located next to each other with their centers 16.5 cm apart. What gravitational force do they exert on each other? Assume
G
= 6.67×10
-11
N·m
2
/kg
2
.
a.
1.6×10
-8
N
b.
9.7×10
-8
N
c.
9.7×10
-8
N/m
2
d.
3.1×10
-7
N
Hint
3.
Two balls have their centers 3.0 m apart. One ball has a mass of 2.7 kg. The other has a mass of 4.5 kg. What is the gravitational force between them? Assume
G
= 6.67×10
-11
N·m
2
/kg
2
.
a.
2.7×10
-10
N
b.
1.3×10
-11
N
c.
9.0×10
-11
N
d.
9.0×10
-10
N
Hint
4.
Assume that you have a mass of 45.0 kg and Earth has a mass of 5.97×10
-11
kg. The radius of Earth is 6.38×10
6
m. What is the force of gravitational attraction between you and Earth? Use
G
= 6.67×10
-11
N·m
2
/kg
2
.
a.
9.80 N
b.
6.60×10
2
N
c.
2.80×10
2
N
d.
4.40×10
2
N
Hint
5.
The attractive force that exists between all objects is known as __________.
a.
centripetal force
b.
the normal force
c.
torque
d.
gravitational force
Hint
6.
In Figure 7-5, if the radius of the planet's orbit were doubled, what effect would it have on its period of orbit?
a.
It would have no effect.
b.
More information is needed to determine the answer.
c.
It would decrease.
d.
It would increase.
Hint
7.
Two 1.00-kg masses have their centers 1.00 m apart. What is the force of attraction between them?
a.
9.7×10
-8
N
b.
1.33×10
-10
N
c.
6.67×10
-11
N
d.
6.67×10
11
N
Hint
8.
According to Kepler's laws, an imaginary line from the Sun to a planet __________.
a.
sweeps out equal areas in equal time periods
b.
sweeps out smaller areas when the planet is closest to the Sun than it would in the same time interval when farthest from the Sun
c.
remains a constant length through the entire orbit of that planet
d.
sweeps out larger areas the greater the planet's distance from the Sun than it would in the same time interval when closest to the Sun
Hint
9.
In Figure 7-5, if the mass of the planet were doubled, what effect would it have on its period of orbit?
a.
The new period would be twice the original period.
b.
The new period would be one-quarter of the original period.
c.
It would have no effect.
d.
The new period would be one-half of the original period.
Hint
10.
Which of the following equations describes one of Kepler's laws?
a.
(
T
A
/
T
B
)
2
= (
r
A
/
r
B
)
3
b.
(
T
A
/
r
A
)
2
= (
T
B
/
r
B
)
3
c.
(
T
A
/
T
B
)
3
= (
r
A
/
r
B
)
2
d.
(
T
B
/
T
A
)
2
= (
r
A
/
r
B
)
3
Hint
11.
According to Kepler's laws, the paths of the planets are __________.
a.
Earth-centered
b.
ellipses
c.
parabolas
d.
circles
Hint
12.
In Newton's equation,
F
=
Gm
1
m
2
/
r
2
,
r
is __________.
a.
the difference in the two masses
b.
a universal constant
c.
the distance between a planet and the Sun
d.
the distance between the centers of the masses
Hint
13.
Which of the following equations represents Newton's law of universal gravitation?
a.
G
=
Fm
1
m
2
/
r
2
b.
F
=
Gm
1
m
2
/
r
2
c.
T
2
= (4
π
2
/
Gm
s
)
r
3
d.
T
3
= (4
π
2
/
Gm
s
)
r
2
Hint
14.
If the mass of a planet near the Sun were doubled, the force of attraction would __________.
a.
be squared
b.
be one half as strong
c.
be doubled
d.
remain constant
Hint
15.
In 1798, __________ devised an apparatus to measure the gravitational force.
a.
Isaac Newton
b.
Johannes Kepler
c.
Henry Cavendish
d.
Tycho Brahe
Hint
16.
In Figure 7-5, if the mass of the Sun were doubled, what effect would it have on the planet's period of orbit?
a.
The new period would be twice the original period.
b.
The new period would be one divided by the square root of two times the original period.
c.
It would have no effect.
d.
The new period would be one-half of the original period.
Hint
17.
According to Kepler's laws, which of the following statements is true?
a.
Planets move slower when they are closer to the Sun and faster when they are farther away.
b.
All points on the path of the planet's orbit are equidistant from the Sun.
c.
Planets move faster when they are closer to the Sun and slower when they are farther away.
d.
Planets orbit at constant velocity.
Hint
18.
According to Newton's law of universal gravitation in the case of a planet near the Sun, which of the following would cause the attractive force to be quadrupled?
a.
double the distance from the Sun
b.
square the mass of the planet
c.
quadruple the distance from the Sun
d.
quadruple the mass of the planet
Hint
