Choose the best answer to each question and write the appropriate letter in the space provided.

 1)  Newton had the insight to see that the __________.
 A) moon always keeps one side toward Earth 
B) moon orbits Earth 
C) moon is moving 
D) force on the moon has the same nature as the force on an apple 
E) none of the above
 
2)  Newton hypothesized that the moon __________.
 
A) is a projectile 
B) is actually attracted to Earth 
C) is falling around Earth 
D) has tangential velocity that prevents it from falling into Earth 
E) all of the above
 
3)  Newton reasoned that the gravitational attraction between Earth and the moon must be __________.
 
A) directly proportional to distance 
B) reduced by distance 
C) the same at all distances 
D) independent of distance
E) all of the above
 
4)  If the mass of Earth increased, with no change in radius, your  weight would __________.
 
A) increase also
 B) decrease
 C) stay the same
 
5)  If the radius of Earth decreased, with no change in mass, your weight would __________.
 
A) increase
 B) not change
 C) decrease
 
6)  If Earth's mass decreased to one half its original mass, with no change in radius, then your weight would __________.
 
A) decrease to one quarter your original weight 
B) decrease to one half your original weight 
C) stay the same 
D) none of the above
 
7)  According to Newton's laws, a rock and a pebble will fall at the same acceleration in a gravitational field because __________.
 
A) the gravitational force on each is the same 
B) the ratio of force/mass is the same for both 
C) both A and B 
D) none of the above
 
8)  A very massive object A and a less massive object B move toward each other under the influence of mutual gravitation. Which force, if either, is greater?
 
A) The force on A 
B) The force on B 
C) Both forces are the same.
 
9)  Two objects move toward each other because of gravitational attraction. As the objects get closer and closer, the force between them __________.
 
A) increases 
B) decreases 
C) remains constant
 
10)  Gravitational forces are the weakest forces found in nature.  Because of this __________.
 
A) the gravitational effect between a pencil and the earth cannot be seen 
B) there is no gravitational force between two 1-kg masses 
C) there is no movement between two 1-kg masses located near each other in space 
D) gravitational effects occur only when a large mass is involved 
E) gravitational forces that are easily observed involve one or more large masses 
 
11)  Suppose the gravitational force between two massive spheres is 10 N. If the distance between the spheres is cut in half, what is the force between the masses?
 
A) 40 N
 B) 20 N
 C) 10 N
 D) 5 N
 E) 2.5 N
  
12)  By noticing that Uranus's orbit is perturbed and by using the law of gravitation, two astronomers independently discovered __________.
 
A) Uranus has several moons 
B) Pluto 
C) exceptions to the law of gravitation 
D) the law of gravitation fails at large distances 

 

13)  The force of gravity acting on you will increase if you __________.
 
A) burrow deep inside the planet
B) stand on a planet with a radius that is shrinking
C) both A and B
D) none of the above
 
14)  The force of gravity on you is greatest when you are standing __________.
 
A) just above Earth's surface
B) just below Earth's surface
C) on Earth's surface
 

15)  The reason the moon does not fall into Earth is that __________.
 

A) Earth's gravitational field at the moon is weak
B) gravitational pull of other planets keeps the moon up
C) the moon has a sufficiently large orbital speed
D) the moon has less mass than the earth
E) none of the above
 
16)  A lunar month is about 28 days. If the moon were closer to Earth than it is now, the lunar month would be __________.
 
A) less than 28 days
B) more than 28 days
C) unchanged at 28 days
 
17)  A hollow spherical planet is inhabited by people who live inside it, where the gravitational field is zero. When a very massive space ship lands on the planet's surface, the gravitational field inside the planet is __________.
 
A) still zero
B) nonzero, directed toward the spaceship
C) nonzero, directed away from the spaceship
 
18)  A supplier wants to make a profit by buying metal by weight at one altitude and selling it at the same price per pound at another altitude. The supplier should __________.
 
A) buy at a high altitude and sell at a low altitude
B) buy at a low altitude and sell at a high altitude
C) disregard altitude because it has a negligible effect
 
19)  Each of us weighs a tiny bit less on the ground floor of a skyscraper than we do on the top floor. One reason for this is that __________.
 
A) the gravitational field is shielded inside the building
B) the mass of the building attracts you upward slightly
C) both A and B
D) none of the above
 
20)  Compare the gravitational force between Earth and Mars, and the gravitational force between a newborn baby and the doctor who holds it. The greater force is between  __________.
 
A) Earth and Mars
B) the baby and the doctor
C) cannot be determined

21)  Consider the gravitational force between the earth and a meteor in outer space. If the meteor moves so its distance from the earth's center doubles, the gravitational force on the meteor will be __________.
 
A) one quarter
B) half
C) double
D) quadruple
E) eight times greater
 
22)  Which is more, the gravitational force between Earth and the moon, or between Earth and the sun?

A) Earth-sun
B) Earth-moon
C) equal
 
23)  Jupiter has more than 300 times the mass of Earth. Yet on Jupiter's surface an object weighs only about 3 times as much as it would on Earth. The explanation to this involves Jupiter's __________.
 
A) large radius
B) low density
C) greater distance from the sun
 

 

24)  If you stood atop a ladder on Earth that was as tall as Earth's radius (so you were twice as far from Earth's center) your weight atop the ladder would be __________.
 
A) half its normal value
B) one-quarter its normal value
C) one-eighth its normal value
D) none of the above
 
25)  Why did Newton think there was a force acting on the moon?
 
A) Because the moon always keeps one side toward Earth
B) Because the moon moves in a curved path
C) Because there is no air on the moon
D) Because the moon is moving
E) all of the above
 
26)  Since Earth is attracted to the sun, why doesn't it fall into the sun?
 
A) Because it has sufficient tangential velocity
B) Because there is an equal force holding it away from the sun
C) Because it has too much mass to move toward the sun
D) Because it has too much inertia to move toward the sun
E) all of the above
 
27)  A 400-N woman stands on top of a very tall ladder so she is one Earth radius above Earth's surface. How much does she weigh?
 
A) zero
B) 100 N
C) 200 N
D) 400 N
E) none of the above
 
28)  Suppose the gravitational force between two masses is 10 N. If the volume of each mass doubles, while everything else stays the same, what is the force between the masses?
 
A) 40 N
 B) 20 N
 C) 10 N
 D) 5 N
 E) 2.5 N
 
29)  Suppose the gravitational force between two massive spheres is 10 N. If the distance between the spheres is doubled, what is the force between the masses?
 
A) 40 N
B) 20 N
C) 10 N
D) 5 N
E) 2.5 N
 
 
30)  Suppose the gravitational force between two massive spheres is 10 N. If the magnitude of each mass doubles, what is the force between the masses?
 
A) 40 N
B) 20 N
C) 10 N
D) 5 N
E) 2.5 N
 

Write True or False in the space provided.

 
31)  The component of an orbiting satellite's velocity that is parallel to Earth's surface is its tangential velocity.

32)  The force of attraction between two masses depends inversely on the square of the distance between the masses. Any law that has this kind of dependence on distance is called an inverse distance law.

33)  Some scientists think that the universe we live in is oscillating.

34)  If Earth were to disappear, the moon would still orbit the place where Earth was.

35)  There is a force on Earth that is directed toward the sun.

36)  Because Earth is "falling" around the sun, it will eventually crash into it.
 
37)  Because Earth and moon are gravitationally attracted towards each other, they will soon collide.

38)  The force on a ball decreases as the ball moves farther from Earth.

39)  If Earth were its present size but twice as massive, we would weigh less.

On a separate sheet of paper, answer the following questions.

 
40)  The text claims that the moon is falling around Earth. Explain what this means. How is tangential velocity related to this? Why doesn't the moon collide with Earth?
 
41)  Discuss how the force of gravity between two masses depends on the size of their masses and the distance between them. Give a numerical example.
 
42)  If the moon orbited Earth at a distance twice what it is now, would the moon be moving faster, slower, or with the same speed as today? Explain. What would happen to the length of the month?
 
43)  If Earth had twice its present radius and twice its present mass, what would happen to your weight? Explain.
 
 

Answer the following questions in the space provided. Show all work.

 
44)  By what factor would your weight be multiplied if Earth's diameter were 1/ 4 as big and Earth's mass remained unchanged?
 
45)  By what factor would your weight be multiplied if Earth were 1/ 4 as massive and Earth's diameter remained unchanged?

46)  What would a person who weighs  70 N on Earth weigh on a planet that has the same mass as Earth but half its radius?
 
 47)  Imagine you are standing atop a ladder so tall that you are  5 Earth radii from Earth's center. What is your weight at the top of the ladder, relative to your weight on the ground?
   
48)  A woman whose mass is  70 kg on Earth's surface is in a spacecraft at a height of twice Earth's radius (that is, 2 Earth radii) above Earth's surface. What is her mass (not weight) there?
 
49)  A man whose mass is  72 kg is in a spacecraft at a height equal to Earth's diameter (not radius!) above Earth's surface. What is the gravitational force between him and Earth at this distance?