1. Q12.1
The mass of the Moon is 1/81 of the mass of the Earth.
Compared to the gravitational force that the Earth exerts on the Moon, the gravitational force that the Moon exerts on the Earth is
= times greater
2. 81 times greater
3. equally strong
4. 1/81 as great
5. (1/81)2 = 1/6561 as great

2. A12.1
The mass of the Moon is 1/81 of the mass of the Earth.
Compared to the gravitational force that the Earth exerts on the Moon, the gravitational force that the Moon exerts on the Earth is
= times greater
2. 81 times greater
3. equally strong
4. 1/81 as great
5. (1/81)2 = 1/6561 as great

3. Q12.2
The planet Saturn has 100 times the mass of the Earth and is 10 times more distant from the Sun than the Earth is.
Compared to the Earth’s acceleration as it orbits the Sun, the acceleration of Saturn as it orbits the Sun is
times greater
2. 10 times greater
3. the same
4. 1/10 as great
5. 1/100 as great

4. A12.2
The planet Saturn has 100 times the mass of the Earth and is 10 times more distant from the Sun than the Earth is.
Compared to the Earth’s acceleration as it orbits the Sun, the acceleration of Saturn as it orbits the Sun is
times greater
2. 10 times greater
3. the same
4. 1/10 as great
5. 1/100 as great

5. Q12.3
Compared to the Earth, Planet X has twice the mass and twice the radius.
This means that compared to the Earth, Planet X has
1. 4 times the surface gravity
2. twice the surface gravity
3. the same surface gravity
4. 1/2 as much surface gravity
5. 1/4 as much surface gravity

6. A12.3
Compared to the Earth, Planet X has twice the mass and twice the radius.
This means that compared to the Earth, Planet X has
1. 4 times the surface gravity
2. twice the surface gravity
3. the same surface gravity
4. 1/2 as much surface gravity
5. 1/4 as much surface gravity

7. Q12.4
A satellite is moving around the Earth in a circular orbit. Over the course of an orbit, the Earth’s gravitational force
1. does positive work on the satellite
2. does negative work on the satellite
3. does positive work on the satellite during part of the orbit and negative work on the satellite during the other part
4. does zero work on the satellite at all points in the orbit

8. A12.4
A satellite is moving around the Earth in a circular orbit. Over the course of an orbit, the Earth’s gravitational force
1. does positive work on the satellite
2. does negative work on the satellite
3. does positive work on the satellite during part of the orbit and negative work on the satellite during the other part
4. does zero work on the satellite at all points in the orbit

9. Q12.5
A planet (P) is moving around the Sun (S) in an elliptical orbit. As the planet moves from aphelion to perihelion, the Sun’s gravitational force
1. does positive work on the planet
2. does negative work on the planet
3. does positive work on the planet during part of the motion from aphelion to perihelion and negative work on the planet during the other part
4. does zero work on the planet at all points between aphelion and perihelion

10. A12.5
A planet (P) is moving around the Sun (S) in an elliptical orbit. As the planet moves from aphelion to perihelion, the Sun’s gravitational force
1. does positive work on the planet
2. does negative work on the planet
3. does positive work on the planet during part of the motion from aphelion to perihelion and negative work on the planet during the other part
4. does zero work on the planet at all points between aphelion and perihelion

11. Q12.6
A planet (P) is moving around the Sun (S) in an elliptical orbit. As the planet moves around the orbit, the planet’s angular momentum
1. increases as it moves from aphelion to perihelion and decreases as it moves from perihelion to aphelion
2. decreases as it moves from aphelion to perihelion and increases as it moves from perihelion to aphelion
3. increases at all times
4. decreases at all times
5. remains the same at all times

12. A12.6
A planet (P) is moving around the Sun (S) in an elliptical orbit. As the planet moves around the orbit, the planet’s angular momentum
1. increases as it moves from aphelion to perihelion and decreases as it moves from perihelion to aphelion
2. decreases as it moves from aphelion to perihelion and increases as it moves from perihelion to aphelion
3. increases at all times
4. decreases at all times
5. remains the same at all times

13. A satellite orbits the earth with constant speed at height above the surface equal to the earth’s radius. The magnitude of the satellite’s acceleration is
gon earth.
2. gon earth.
3. gon earth.
4. 2gon earth.
5. 4gon earth.
STT12.1

14. A satellite orbits the earth with constant speed at height above the surface equal to the earth’s radius. The magnitude of the satellite’s acceleration is
gon earth.
2. gon earth.
3. gon earth.
4. 2gon earth.
5. 4gon earth.
STT12.1

15. The figure shows a binary star system
The figure shows a binary star system. The mass of star 2 is twice the mass of star 1. Compared to , the magnitude of the force is
1. one quarter as big.
2. half as big.
3. twice as big.
4. four times as big.
5. the same size.
STT12.2

16. The figure shows a binary star system
The figure shows a binary star system. The mass of star 2 is twice the mass of star 1. Compared to , the magnitude of the force is
1. one quarter as big.
2. half as big.
3. twice as big.
4. four times as big.
5. the same size.
STT12.2

17. A planet has 4 times the mass of the earth, but the acceleration due to gravity on the planet’s surface is the same as on the earth’s surface. The planet’s radius is
Re.
Re.
3. Re.
4. 2Re.
5. 4Re.
STT12.3

18. A planet has 4 times the mass of the earth, but the acceleration due to gravity on the planet’s surface is the same as on the earth’s surface. The planet’s radius is
Re.
Re.
3. Re.
4. 2Re.
5. 4Re.
STT12.3

19. 1. Ue > Ua = Ub = Ud > Uc 2. Ub > Uc > Ua = Ud > Ue
Rank in order, from largest to smallest, the absolute values |Ug| of the gravitational potential energies of these pairs of masses. The numbers give the relative masses and distances.
In absolute value:
1. Ue > Ua = Ub = Ud > Uc
2. Ub > Uc > Ua = Ud > Ue
3. Ub > Uc > Ud > Ua > Ue
4. Ue > Ua = Ub >Uc > Ud
5. Ue > Ud > Ua > Ub = Uc
STT12.4

20. 1. Ue > Ua = Ub = Ud > Uc 2. Ub > Uc > Ua = Ud > Ue
Rank in order, from largest to smallest, the absolute values |Ug| of the gravitational potential energies of these pairs of masses. The numbers give the relative masses and distances.
In absolute value:
1. Ue > Ua = Ub = Ud > Uc
2. Ub > Uc > Ua = Ud > Ue
3. Ub > Uc > Ud > Ua > Ue
4. Ue > Ua = Ub >Uc > Ud
5. Ue > Ud > Ua > Ub = Uc
STT12.4

21. Two planets orbit a star
Two planets orbit a star. Planet 1 has orbital radius r1 and planet 2 has r2 = 4r1. Planet 1 orbits with period T1. Planet 2 orbits with period
1. T2 = T1/2.
2. T2 = T1.
3. T2 = 2T1.
4. T2 = 4T1.
5. T2 = 8T1.
STT12.5

22. Two planets orbit a star
Two planets orbit a star. Planet 1 has orbital radius r1 and planet 2 has r2 = 4r1. Planet 1 orbits with period T1. Planet 2 orbits with period
1. T2 = T1/2.
2. T2 = T1.
3. T2 = 2T1.
4. T2 = 4T1.
5. T2 = 8T1.
STT12.5

23. Chapter 12
Reading Quiz

24. Who discovered the basic laws of planetary orbits?
1. Newton
2. Kepler
3. Faraday
4. Einstein
5. Copernicus
IG12.1

25. Who discovered the basic laws of planetary orbits?
1. Newton
2. Kepler
3. Faraday
4. Einstein
5. Copernicus
IG12.1

26. What is geometric shape of a planetary or satellite orbit?
1. Circle
2. Hyperbola
3. Sphere
4. Parabola
5. Ellipse
IG12.2

27. What is geometric shape of a planetary or satellite orbit?
1. Circle
2. Hyperbola
3. Sphere
4. Parabola
5. Ellipse
IG12.2

28. The gravitational force between two objects of masses m1 and m2 that are separated by distance r is
1. proportional to r.
2. proportional to 1/r.
3. proportional to 1/r2.
4. (m1 + m2)g.
5. (m1 + m2)G.
IG12.3

29. The gravitational force between two objects of masses m1 and m2 that are separated by distance r is
1. proportional to r.
2. proportional to 1/r.
3. proportional to 1/r2.
4. (m1 + m2)g.
5. (m1 + m2)G.
IG12.3

30. The value of g at the height of the space shuttle’s orbit is
m/s2.
2. slightly less than 9.8 m/s2.
3. much less than 9.8 m/s2 .
4. exactly zero.
IG12.4

31. The value of g at the height of the space shuttle’s orbit is
m/s2.
2. slightly less than 9.8 m/s2.
3. much less than 9.8 m/s2.
4. exactly zero.
IG12.4