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

1)
If the mass of the earth increased, with no change in radius, your weight would __________.
A)
increase also

B) decrease

C) stay the same

2)
If the radius of the earth decreased, with no change in mass, your weight would __________.
A)
increase

B) decrease

C) not change

3)
According to Newton's laws, a rock and a pebble will fall with the same acceleration in a gravitational field because the gravitational force on each is __________.
A)
the same
B)
different, though the ratio of the force to the mass of each is the same
C)
none of the above

4)
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

5)
The value of the acceleration due to gravity, g, __________.
A)
depends on the radius of Earth
B)
depends on the mass of Earth
C)
depends on the universal gravitational constant, G

D) is different on different planets
E)
all of the above

6)
We can tell if a gravitational force exists in a region of space if __________.
A)
we let go of a ball and it starts to move
B)
we disturb a pendulum and it starts swinging
C)
a force exists on a mass placed there
D)
we can weigh ourselves
E)
all of the above

7)  Gravitational field lines show the __________.
A)
direction a mass would be accelerated
B)
direction of the field at each point
C)
direction of the force on any mass
D)
strength of the field
E)
all of the above

8)
Compared to the gravitational field on the surface of Earth, the gravitational field well below Earth's surface is __________.
A)
larger

B) smaller

C) the same

9)
The gravitational field strength at the center of Earth is __________.
A)
large
B)
the same as on the surface
C)
smaller than on the surface but still larger than zero
D)
zero

10)
If you were to weigh yourself in an elevator that is accelerating upward, compared to your ordinary weight you would weigh __________.
A)
more

B) the same
C)
less, but more than zero

D) zero

11)  If you drop a stone into a hole drilled all the way to the other side of Earth, the stone will __________.
A)
stop at the center of Earth
B)
speed up until it gets to the center of Earth
C)
speed up until it reaches the other side of Earth
D)
slow down until it reaches the center of Earth

12)
Ocean tides occur mainly because __________.
A)
water normally runs to the side of Earth away from the sun
B)
of the gravitational pull of the sun on Earth
C)
of different gravitational pulls of the moon on opposite sides of Earth
D)
as Earth rotates it leaves the ocean water somewhat behind it
E)
none of the above

13)
The affect of the sun's pull on the earth's oceans is much less visible than that of the moon's pull because __________.
A)
Earth is orbiting so fast
B)
Earth is spinning so fast
C)
the sun is so far away
D)
the sun is radiating a lot of energy
E)
none of the above

14)
A lunar eclipse happens when __________.
A)
the sun is between Earth and the moon
B)
the moon is between Earth and the sun
C)
Earth is between the moon and the sun

15)
A solar eclipse happens when __________.
A)
the sun is between Earth and the moon
B)
the moon is between Earth and the sun
C)
Earth is between the moon and the sun

16)
Earth tides in which the solid surface of Earth rises and falls are caused by __________.
A)
many volcanic eruptions
B)
the motion of water caused by ocean tides
C)
different forces between opposite parts of Earth and the moon
D)
the alignment of the sun and the moonE) Nonsense! The solid surface of Earth cannot have tides.

17)
Suppose the moon had twice its present mass and still orbited Earth at the same distance. In that case
A)
the ocean tide facing the moon would rise, and the other tide would lower
B)
the ocean tide facing the moon would lower, and the other tide would rise
C)
both ocean tides would be smaller
D)
both ocean tides would be higher
E)
the ocean tides would be the same as they are now

18)
Suppose the moon were covered with water and orbited Earth as it now does. In that case the moon would have __________.
A)
one tidal bulge
B)
two tidal bulges
C)
three tidal bulges
D)
four tidal bulges
E)
no tidal bulges

19)
During an eclipse of the sun, when the moon comes between the sun and Earth, the ocean tide nearest the moon would be __________.
A)
extra high
B)
extra low
C) both A and B
D)
the same as always

20)
There would still be two ocean tides per 24 hours if __________.
A)
Earth and moon had equal masses
B)
the moon had more mass than Earth
C)
the sun's influence on the tides were negligible
D)
all of the above
E)
none of the above

21)
There are two main processes going on in the sun that keep the sun in existence. These processes are gravitation and  __________.
A)
electrostatic repulsion
B)
nuclear fusion
C)
heat absorbtion

22)
A black hole is an object that __________.
A)
has an enormous density
B)
has an escape speed greater than the speed of light
C)
has an enormous gravitational field near it
D)
alters the space around it
E)
all of the above

23)
The factor most directly responsible for making a black hole invisible is its __________.
A)
size
B)
mass
C)
color
D)
surface escape velocity
E)
none of the above

24)
If the sun were to collapse to form a black hole (quite unlikely), Earth would __________.
A)
be drawn into the black hole
B)
spiral into the black hole
C)
orbit the black hole just as it orbits the sun now
D)
leave the solar system in the direction of its tangential velocity
E)
immediately disappear

25)
When a star collapses to form a black hole, its mass __________.
A)
increases
B)
decreases
C)
remains the same

26)
Gravitation weakens as the inverse square of distance, while tidal gravity (force per kilogram) weakens with the inverse __________.
A)
of distance
B)
square of distance
C)
cube of distance
27)
In order for tidal gravity to be significant, there must be a relatively large distance between

A)
opposite sides of the body experiencing tides
B)
the body causing tides and the body experiencing tides
C)
both A and B
D)
none of the above

28)
Which produces a greater tidal effect in your body, the moon or a 1-kg melon that you hold above your head?
A)
The moon
B)
The melon
C)
Not enough information is given to make a reasonable estimate

29)
Which of these three produces a greater tidal effect on you right now?
A)
The moon
B)
The sun
C)
Earth

30)
A woman who weighs 400 N at Earth's surface 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

31)
If Earth had twice its present mass, but the same radius, what would be the value of g?
A)
39.2  m/s to power of (2)
B)
19.6  m/s to power of (2)
C)
9.8  m/s to power of (2)
D)
4.9  m/s to power of (2)
E)
0  m/s to power of (2)

32)
How many high tides are there normally each day on an typical ocean beach?
A)
4

B) 2

C) 1

D) 0

33)
If the radius of Earth were one half what it is now, and the mass were the same, what would be the value of g?
A)
39.2  m/s to power of (2)
B)
19.6  m/s to power of (2)
C)
9.8  m/s to power of (2)
D)
4.9  m/s to power of (2)
E)
0  m/s to power of (2)

Write True or False in the space provided.

34)
When the properties of space are altered in such a way that a mass in that space experiences a force, the space is said to contain a gravitational field.

35)
When Earth's shadow falls on the moon, a lunar eclipse occurs.

36)
When the moon's shadow falls on Earth, a lunar eclipse occurs.

37)
A neap tide occurs when Earth, the sun, and the moon are lined up.

38)
A spring tide occurs when the attractions of the sun and moon are at right angles to each other.

39)
For some massive stars, gravitational collapse doesn't stop until the density of the star becomes so enormous that even light cannot escape. Such a star becomes a black hole.

40)
The sun actually pulls harder on Earth's oceans than the moon.

41)  The acceleration due to gravity depends only on the mass of Earth.

42)
If Earth had its present mass but twice the radius, the acceleration due to gravity would increase.

43)  Because Earth has mass, it also has a gravitational field.

44)  A skydiver jumping from a plane falls in a direction opposite to Earth's gravitational field.

45)  Ocean tides are caused by differences in the gravitational pull between the moon and the opposite sides of Earth.

46)  If the moon had oceans as deep as Earth's, tides on the moon would be about the same height as Earth's tides.

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

47)  Explain what a gravitational field is. How could you measure the strength of the field using ordinary equipment? How is weight related to the gravitational field strength?

48)
Suppose you dropped an object into a hole bored completely through the center of Earth to the other side. What would happen to the object? Where is the acceleration the largest? The least? Where is velocity the largest? The least?

49)
Suppose you are riding on a roller coaster at an amusement park. Discuss how your apparent weight would change as the car accelerates up the track and then coasts back down. What would your apparent weight be if the car were momentarily in free fall?

50)
Explain why there are ocean tides, and discuss the three types of tides (regular, spring, and neap).

51)
Explain how a black hole is formed, and discuss the gravitational field surrounding it. How is it related to the field before the star collapsed?

Answer the following questions in the space provided. Show all work.
52)
Jupiter has a mass about 300 times that of Earth, and its radius is about 11 times that of Earth. What would be the approximate weight of a  2.5-kg rock on the surface of Jupiter?

53)
Satellites often hover 640 km above Earth's surface, which is 10% of Earth's radius. What is Earth's approximate gravitational field, g, in satellite territory?54)  What is Earth's gravitational field, g,  4 Earth-diameters  from Earth's surface ( 9r from Earth's center)?

55)
Suppose you're standing on the surface of a shrinking planet. If it shrinks to 1/ 3 its diameter (and its mass remains the same), how many times as much would you weigh on the shrunken surface?

56)  The tidal force of the moon on you right now is about 3.0 x  10 to power of (-13) N/kg. If the moon were 1/ 5 as far away, what would be the moon's tidal force on you?

57)
The tidal force of Earth on you is about 6 x  10 to power of (-6) N/kg. If Earth's mass were the same but its diameter  5 times as great, what would be Earth's tidal force on you? If you have any questions, please email Ms. Cummings