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