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Total questions: 139

Worksheet time: 3hrs 2mins

Name
Class
Date
1.

Which would hit the ground first if dropped from the same height in a vacuum—a feather or a metal bolt?

a)

the feather

b)

the metal bolt

c)

They would hit the ground at the same time.

d)

They would be suspended in a vacuum.

2.

The state that exists when the only force acting on an object is gravity is called

a)

momentum

b)

acceleration

c)

inertia

d)

free fall

3.

The more mass an object has, the faster it will fall.

a)

Aristotle - TRUE; Galileo - TRUE

b)

Aristotle - FALSE; Galileo - FALSE

c)

Aristotle - TRUE; Galileo - FALSE

d)

Aristotle - FALSE; Galileo - TRUE

4.

What shape is Earth's orbit?

a)

circle

b)

ellipse

c)

square

d)

spiral

5.

The law of universal gravitation is credited to whom?

a)

Einstein

b)

Galileo

c)

Cavendish

d)

Newton

6.

Who of the following first described the shape of the earth's orbit?

a)

Aristotle

b)

Kepler

c)

Galileo

d)

Newton

7.
Two factors effecting the magnitude of force of gravity between 2 objects are...
a)
weight and mass 
b)
distance and weight 
c)
mass and matter 
d)
mass and distance 
8.
If a bowling ball and a feather were dropped at the same time, in a room with no air resistance (vacuum), which object will hit the ground first?
a)
Bowling Ball
b)
Feather
c)
Both would hit at the same time
d)
Neither one would hit the ground because air is what pushing things down.
9.

Who is credited with discovering the Gravitational constant, even though he got it wrong at first for measuring edge to edge and not center to center?

a)

Galileo

b)

Kepler

c)

Newton

d)

Cavendish

10.

The gravitational constant used in the Universal Gravitation Formula is:

a)

6.63 x 10-34

b)

6.02 x 10-23

c)

6.67 x 10-11

d)

6.65 x 10-29

11.

Who came first?

a)

Einstein

b)

Galileo

c)

Cavendish

d)

Newton

12.

Who described gravity as a field around masses?

a)

Einstein

b)

Galileo

c)

Cavendish

d)

Newton

13.

Who was Kepler?

a)

Scientist

b)

Chemist

c)

German Astronomer and mathematician

d)

Journalist

14.
If you double the mass of an object with the same force apply on it, the acceleration will
a)
double
b)
cut in half
c)
the same
d)
zero
15.
A book weighs 4 N. When held at rest in your hands, the net force on the book is
 
a)
0 N.
b)
 0.4 N.
c)
 4 N.
d)
 39 N.
16.
The force that draws all objects towards Earth.
a)
friction
b)
gravity
c)
mass
d)
acceleration
17.
Who invented the 3 Laws of Motion?
a)
Sir Francis Bacon
b)
Sir Isaac Newton
c)
Johannes Kepler
d)
Galileo Galilei
18.
The SI units for force are...
a)
Kilograms
b)
Newtons
c)
Meters per second
d)
Pounds
19.
Planets orbit the Sun in a shape called a(n)
a)
circle
b)
ellipse
c)
focus
d)
perihelion
20.
An ellipse is drawn around two points called
a)
aphelion
b)
perihelion
c)
foci
d)
axis
21.
Where is the planet moving faster
a)
Position A to B
b)
Position B to C
c)
Position H to I
d)
Position I to J
22.
What has an eccentricity of zero
a)
a straight line
b)
a large ellipse
c)
a circle
d)
a small ellipse
23.

Kepler's 2nd Law deals with

a)

the shape of the planets' orbits

b)

the area the planet travels

c)

the length of time/period it takes the planet to orbit the sun

24.
A planet moves __________ when it is farthest from the sun.
a)
faster
b)
slower
25.
The farther away a planet is from the sun, the _______ it takes it to orbit the sun once. 
a)
longer
b)
shorter
26.

What does Kepler's 1st Law state?

a)

all planets move in elliptical shaped orbits around the sun

b)

all ellipses have one foci

c)

the area that a planet revolves around the sun is equal

d)

the speed that a planet revolves around the sun changes

27.
A perfect circle has an eccentricity of ______.
a)
0
b)
.99
c)
1
d)
2
28.
Kepler's first law states that the orbits of the planets around the sun are 
a)
Circles
b)
Ellipses
c)
Spheres
d)
irregular shapes
29.
How does changing the mass of objects affect the force of gravity?
a)
Increasing mass will decrease gravity
b)
Decreasing mass will increase gravity
c)
Mass will not affect gravity
d)
Increasing mass increases gravity
30.
How does changing the distance between objects affect the force of gravity?
a)
Decreasing distance increases gravity
b)
increasing distance increases gravity 
c)
Distance does not affect gravity
31.
The point in Earth's orbit when it is closest to the sun is called the
a)
Aphelion
b)
perihelion
c)
maximum ellipse
d)
minimum elipse
32.
Why does the moon orbit the Earth and not the Sun?
a)
The Earth is bigger than the Sun
b)
The sun is too close to the moon
c)
The Earth is closer to the moon.
d)
The Sun did not exist when the moon formed
33.
When the distance between foci is increased, what happens to the shape of the ellipse?
a)
it gets rounder
b)
it gets flatter
c)
its major axis decreases
d)
its minor axis increases
34.
How many laws of planetary motion did Kepler discover?
a)
1
b)
2
c)
3
d)
4
35.
Which scientist discovered the law of gravitational attraction?
a)
Kepler
b)
Brahe
c)
Galileo
d)
Newton
36.
Complete the following statement: The farther away two planets are the _______ the gravitational force between them.
a)
more
b)
same
c)
dosen't matter
d)
less
37.

Which configuration will result in the greatest gravitational force?

a)

small masses far apart

b)

large masses far apart

c)

small masses close together

d)

large masses close together

38.
What happens to Gravitational force if I double both of the masses but don't change their distance?
a)
doubles
b)
half as big
c)
4x bigger
d)
4x smaller
39.

Calculate the gravitational force between two objects when they are 0.750m apart. Each object has a mass of 5.00kg.

a)

2.96x10-7N

b)

3.00x10-9N

c)

2.22x10-9N

d)

2.23x10-8N

40.
Two objects are attracted to each other with 36 N of gravitational force.
What would the force between them be if the distance between them were doubled?
a)
9
b)
18
c)
72
d)
144
41.

Two spherical objects have masses of 8000 kg and 1500 kg. Their centers are separated by a distance of 1.5 m. Find the gravitational attraction between them

a)

5.4 X 10-4 N

b)

1.2 X 107 N

c)

3.6 X 10-4 N

d)

5.33 N

42.
Complete the following statement: The farther away two planets are the _______ the gravitational force between them.
a)
more
b)
same
c)
dosen't matter
d)
less
43.

Which configuration will result in the greatest gravitational force?

a)

small masses far apart

b)

large masses far apart

c)

small masses close together

d)

large masses close together

44.

How is the gravitational force between to objects related to their mass

a)

They are directly proportional

b)

They are inversely proportional

c)

They do not affect each other

d)

They are equal

45.

A 500 kg asteroid is located 3.4 x107m from the center of Earth. The mass of Earth is 6.0x1024 kg. What is the gravitational force between the asteroid and Earth?

F = GMm/r2

G= 6.67 x 10-11

a)

1.73 x 102 N

b)

4.63 x 105 N

c)

2.94 x 103 N

d)

6.42 x 104 N

46.

If I double the mass of one object, but don't change anything else... What happens to the gravitational force between two objects?

a)

Doubles

b)

Quadruples

c)

Cut in Half

d)

4x Smaller

47.

The law of universal gravitation is credited to whom?

a)

Einstein

b)

Galileo

c)

Darwin

d)

Newton

48.

Two asteroids exert a gravitational force, F, on each other. Some time later, the asteroids are now three times as far from each other as before. Which of the following represents the gravitational force at this distance?

a)

F/3

b)

F/2

c)

F/6

d)

F/9

49.
Force of gravity is directly proportional to
a)
Mass
b)
Weight
c)
Distance
d)
Time
50.
If Earth's mass was cut in half, what would happen to your mass?
a)
increase because gravitational force increases
b)
decrease because gravitational force decreases
c)
decrease because gravitational force increases
d)
nothing, mass is not affected by gravitational force
51.
Double the mass of an object, what happens to the force of attraction?
a)
4 times stronger gravity force
b)
4 times weaker gravity force
c)
2 times weaker gravity force
d)
2 times stronger gravity force
52.

Two masses m1 and m2 are separated by a distance R and gravitaional force between them is F. If the distance R is reduced to R/2 the force will now be

a)

8F

b)

2F

c)

F/4

d)

F/2

e)

4F

53.
Two objects are attracted to each other with 36 N of gravitational force.
What would the force between them be if the distance between them were doubled?
a)
9
b)
18
c)
72
d)
144
54.
Two factors effecting the magnitude of the force of gravity between 2 objects are...
a)
mass and distance 
b)
mass and matter
c)
distance and weight 
d)
weight and mass
55.

Two spherical objects have masses of 8000 kg and 1500 kg. Their centers are separated by a distance of 1.5 m. Find the gravitational attraction between them

a)

5.4 X 10-4 N

b)

1.2 X 107 N

c)

3.6 X 10-4 N

d)

5.33 N

56.
Complete the following statement: The farther away two planets are the _______ the gravitational force between them.
a)
more
b)
same
c)
dosen't matter
d)
less
57.

Which configuration will result in the greatest gravitational force?

a)

small masses far apart

b)

large masses far apart

c)

small masses close together

d)

large masses close together

58.

How is the gravitational force between to objects related to their mass

a)

They are directly proportional

b)

They are inversely proportional

c)

They do not affect each other

d)

They are equal

59.

If I double the mass of one object, but don't change anything else... What happens to the gravitational force between two objects?

a)

Doubles

b)

Quadruples

c)

Cut in Half

d)

4x Smaller

60.

The law of universal gravitation is credited to whom?

a)

Einstein

b)

Galileo

c)

Darwin

d)

Newton

61.
Force of gravity is directly proportional to
a)
Mass
b)
Weight
c)
Distance
d)
Time
62.
If Earth's mass was cut in half, what would happen to your mass?
a)
increase because gravitational force increases
b)
decrease because gravitational force decreases
c)
decrease because gravitational force increases
d)
nothing, mass is not affected by gravitational force
63.
Double the mass of an object, what happens to the force of attraction?
a)
4 times stronger gravity force
b)
4 times weaker gravity force
c)
2 times weaker gravity force
d)
2 times stronger gravity force
64.
As distance separating the objects increases the force
a)
increases
b)
decreases
c)
stays the same
65.

The number 6.67 x 10 -11 N* m2 / kg2 is called the

a)

Universal speed constant

b)

centripetal force

c)

Universal Gravitational constant

d)

Earth's Gravitational constant

66.

Calculate the gravitational force between two objects when they are 0.750m apart. Each object has a mass of 5.00kg.

a)

2.96x10-7N

b)

3.00x10-9N

c)

2.22x10-9N

d)

2.23x10-8N

67.
Two objects are attracted to each other with 36 N of gravitational force.
What would the force between them be if the distance between them were doubled?
a)
9
b)
18
c)
72
d)
144
68.
Two factors effecting the magnitude of the force of gravity between 2 objects are...
a)
mass and distance 
b)
mass and matter
c)
distance and weight 
d)
weight and mass
69.

Two spherical objects have masses of 8000 kg and 1500 kg. Their centers are separated by a distance of 1.5 m. Find the gravitational attraction between them

a)

5.4 X 10-4 N

b)

1.2 X 107 N

c)

3.6 X 10-4 N

d)

5.33 N

70.
Complete the following statement: The farther away two planets are the _______ the gravitational force between them.
a)
more
b)
same
c)
dosen't matter
d)
less
71.

How is the gravitational force between to objects related to their mass

a)

They are directly proportional

b)

They are inversely proportional

c)

They do not affect each other

d)

They are equal

72.

The law of universal gravitation is credited to whom?

a)

Einstein

b)

Galileo

c)

Darwin

d)

Newton

73.
Force of gravity is directly proportional to
a)
Mass
b)
Weight
c)
Distance
d)
Time
74.
Double the mass of an object, what happens to the force of attraction?
a)
4 times stronger gravity force
b)
4 times weaker gravity force
c)
2 times weaker gravity force
d)
2 times stronger gravity force
75.
As distance separating the objects increases the force
a)
increases
b)
decreases
c)
stays the same
76.

How is the gravitational force between to objects related to their mass

a)

They are directly proportional

b)

They are inversely proportional

c)

They do not affect each other

d)

They are equal

77.

The law of universal gravitation is credited to whom?

a)

Einstein

b)

Galileo

c)

Darwin

d)

Newton

78.
Force of gravity is directly proportional to
a)
Mass
b)
Weight
c)
Distance
d)
Time
79.
If Earth's mass was cut in half, what would happen to your mass?
a)
increase because gravitational force increases
b)
decrease because gravitational force decreases
c)
decrease because gravitational force increases
d)
nothing, mass is not affected by gravitational force
80.

Two masses m1 and m2 are separated by a distance R and gravitaional force between them is F. If the distance R is doubled the force will now be _

a)

4F

b)

2F

c)

F/2

d)

8F

e)

F/4

81.

Which of these two pairs of objects will have a larger gravitational force?

a)

The top pair, because they are smaller

b)

The bottom pair, because they are more massive

c)

They are the same distance apart, so they will have the same force

82.

Why does the Earth orbit the Sun instead of the Sun orbiting the Earth?

a)

The force of the Sun's gravity is bigger than the Earth's

b)

The force of the Earth's gravity doesn't affect the Sun

c)

The Earth is more massive than the Sun

d)

The Sun is more massive than the Earth

83.

On which planet would you weigh the most?

a)

Pluto, because it it not very massive

b)

Earth, because it is where we live

c)

Jupiter, because it is the most massive planet

d)

Venus, because it has a very thick atmosphere

84.

A comet has a very elliptical orbit (sometimes it's a long way from the Sun and sometimes it comes close to the Sun.) When do you think the comet will be moving the fastest?

a)

When it is a long way from the Sun

b)

When it is closest to the Sun

c)

It will move at the same speed all the time

d)

It changes speed based on gravity, not distance

85.
All objects in the universe attract each other through gravitation force is called...
a)
The Law of Universal Gravitation
b)
The Law of Conservation of Momentum
c)
The Law of Thermodynamics
d)
The Law of Monty the Snake
86.

An object in free fall seems to be ________

a)

not moving

b)

slowed by air resistance

c)

sped up by air resistance

d)

weightless

87.

In the free-body diagram shown, which of the following is the gravitational force acting on the balloon?

a)

5120 N

b)

1520 N

c)

950 N

d)

4050 N

88.

Kepler’s third law states that the ratio of

a)

the orbital period to the orbital radius is the same for all planets.

b)

the orbital periods of any two planets equals the ratio of the orbital radii.

c)

all planets would orbit with the same orbital period.

d)

the period squared to the radius cubed is the same ratio for all planets.

89.

The following diagram shows two smaller planets of mass m and one larger planet of mass 4m, aligned and separated by distance d between each planet.

Planet A experiences a gravitational force by Planet C that is ______ that by Planet B.

a)

less than

b)

equal to

c)

greater than

d)

cannot be determined by the information given

90.

Satellite B is three times more massive than Satellite A. Which satellite experiences a stronger gravitational attraction with the earth?

a)

A due to its mass

b)

A due to its distance

c)

B due to its mass

d)

B due to its distance

91.

The size of the gravitational force between two objects depends on their ____.

a)

Frictional Forces

b)

inertia

c)

masses and the distance between them

d)

speed and direction

92.

When calculating the gravitational force between two extended bodies, you should measure the distance

a)

from the closest points on each body.

b)

from the most distant points on each body.

c)

from the center of each body.

d)

From The center of one object and the edge of the other

93.

In the absence of air, a penny and a feather that are dropped from the same height at the same time will ____.

a)

fall at different rates

b)

fall at the same rate

c)

float

d)

have no momentum

94.

If gravity did NOT affect the path of a horizontally thrown ball, the ball would ____.

a)

go straight up

b)

fall straight down

c)

follow a curved path

d)

travel horizontally

95.

Objects that are falling toward Earth in free fall move

a)

faster and faster

b)

slower and slower

c)

at a constant velocity

d)

slower then faster

96.

An object in free fall seems to be ________

a)

not moving

b)

slowed by air resistance

c)

sped up by air resistance

d)

weightless

97.

What two factors cause planets to move in elliptical orbits?

a)

centripetal force and rotational capacity

b)

inertia and gravity

c)

mass and distance

d)

mass and gravity

98.

Kepler’s third law states that the ratio of

a)

the orbital period to the orbital radius is the same for all planets.

b)

the orbital periods of any two planets equals the ratio of the orbital radii.

c)

all planets would orbit with the same orbital period.

d)

the period squared to the radius cubed is the same ratio for all planets.

99.

The following diagram shows two smaller planets of mass m and one larger planet of mass 4m, aligned and separated by distance d between each planet.

Planet A experiences a gravitational force by Planet C that is ______ that by Planet B.

a)

less than

b)

equal to

c)

greater than

d)

cannot be determined by the information given

100.

Satellite B is three times more massive than Satellite A. Which satellite experiences a stronger gravitational attraction with the earth?

a)

A due to its mass

b)

A due to its distance

c)

B due to its mass

d)

B due to its distance

101.

Which graph best represents the gravitational force F that a rocket experiences as it travels a distance D away from the surface of the earth? Note that RA represents the edge of the atmosphere.

a)

A

b)

B

c)

C

d)

D

102.

A person on Pluto’s surface would experience a(n)_______________gravitational force compared to being on Earth.

a)

weaker, because Pluto is further from the sun

b)

weaker, because Pluto has less mass

c)

equal, because both planets orbit the sun

d)

stronger, because Pluto has a more elliptical orbit

103.

Does an earth-orbiting satellite or the moon experience a greater force of gravity from the Earth?

a)

The satellite, because it is much closer to the earth.

b)

The moon, because it is much more massive.

c)

They experience the same force, because they both orbit the earth.

d)

Neither experiences a force, because they are in space.

104.

Which of the following statements is correct about weight and mass?

a)

Mass and weight both vary with location.

b)

Mass varies with location, but weight does not.

c)

Weight varies with location, but mass does not.

d)

Neither mass nor weight varies with location.

105.

Planets travel at _______________distances and speeds as they orbit the sun.

a)

the same

b)

different, faster when closer, slower when farther away

c)

different, slower when closer, faster when farther away

d)

the same distance but different speeds

106.

When the earth is closest to the sun, it is ____________ and when it is farthest from the sun it is____________.

a)

winter (January), summer (July)

b)

summer (July), winter (December)

c)

fall (September), spring (March)

d)

spring (April), summer (June)

107.

Which of the graphs shows how the force on an object changes if the mass increases and the gravitational acceleration stays constant?

a)

A

b)

B

c)

C

d)

D

108.

Two balls are dropped at the same height. One ball is dropped from table height and the other initially moves horizontally across the table and then falls off the edge, as shown in the figure. If both balls are dropped at exactly the same time, which one will hit the ground first?

a)

Ball A because it has the shortest distance to travel.

b)

Ball B because it is already travelling downward.

c)

A and B hit at same time because gravity pulls all objects the same.

109.

In a heliocentric system, Earth revolves around

a)

Mars

b)

The moon

c)

Stars

d)

The sun

110.

The fact that each planet’s orbit is an ellipse was discovered by

a)

Copernicus

b)

Kepler

c)

Galileo

d)

Brahe

111.

What shape are the orbits of most comets?

a)

long narrow ellipses

b)

nearly circular ellipses

c)

circles

d)

spherical

112.

Copernicus explained that

a)

the sun is at the center of the system of planets.

b)

the sun and the planets revolve around Earth.

c)

the geocentric system is correct.

d)

there are only six planets.

113.

The size of the gravitational force between two objects depends on their ____.

a)

Frictional Forces

b)

inertia

c)

masses and the distance between them

d)

speed and direction

114.

When calculating the gravitational force between two extended bodies, you should measure the distance

a)

from the closest points on each body.

b)

from the most distant points on each body.

c)

from the center of each body.

d)

From The center of one object and the edge of the other

115.

Why does an astronaut weigh less on the moon than on Earth?

a)

The astronaut has less mass on the moon.

b)

The astronaut is farther from Earth’s center when he or she is on the moon.

c)

The gravitational field strength is less on the moon’s surface than on Earth’s surface.

d)

The astronaut is continually in free fall because the moon orbits Earth.

116.

In the absence of air, a penny and a feather that are dropped from the same height at the same time will ____.

a)

fall at different rates

b)

fall at the same rate

c)

float

d)

have no momentum

117.

If gravity did NOT affect the path of a horizontally thrown ball, the ball would ____.

a)

go straight up

b)

fall straight down

c)

follow a curved path

d)

travel horizontally

118.

Which of the following statements applies to the motion of a ball rising and then falling in free fall?

I. The ball has constant acceleration as it moves upward.

II. The ball has zero acceleration at the very top of its path.

III. The ball has constant acceleration as it moves downward.

a)

I only

b)

III only

c)

I and III

d)

I, II, and III

119.

Objects that are falling toward Earth in free fall move

a)

faster and faster

b)

slower and slower

c)

at a constant velocity

d)

slower then faster

120.

An object in free fall seems to be ________

a)

not moving

b)

slowed by air resistance

c)

sped up by air resistance

d)

weightless

121.

In the free-body diagram shown, which of the following is the gravitational force acting on the balloon?

a)

5120 N

b)

1520 N

c)

950 N

d)

4050 N

122.

In the figure shown, according to Kepler’s laws of planetary motion,

a)

A1=A2

b)

Δt1 > Δt2.

c)

if Δt1 = Δt2, then the orbit is circular.

d)

if Δt1 = Δt2, then A1 = A2.

123.

Kepler’s second law states that a line connecting a planet to the sun

a)

is longest in the winter and shortest in the summer.

b)

is longest in the winter and shortest in the summer.

c)

sweeps out the same amount of area in any two equal periods of time.

d)

sweeps out the same amount of area regardless of the planet.

124.

What two factors cause planets to move in elliptical orbits?

a)

centripetal force and rotational capacity

b)

inertia and gravity

c)

mass and distance

d)

mass and gravity

125.

Kepler’s third law states that the ratio of

a)

the orbital period to the orbital radius is the same for all planets.

b)

the orbital periods of any two planets equals the ratio of the orbital radii.

c)

all planets would orbit with the same orbital period.

d)

the period squared to the radius cubed is the same ratio for all planets.

126.

The following diagram shows two smaller planets of mass m and one larger planet of mass 4m, aligned and separated by distance d between each planet.

Planet A experiences a gravitational force by Planet C that is ______ that by Planet B.

a)

less than

b)

equal to

c)

greater than

d)

cannot be determined by the information given

127.

Satellite B is three times more massive than Satellite A. Which satellite experiences a stronger gravitational attraction with the earth?

a)

A due to its mass

b)

A due to its distance

c)

B due to its mass

d)

B due to its distance

128.

Which graph best represents the gravitational force F that a rocket experiences as it travels a distance D away from the surface of the earth? Note that RA represents the edge of the atmosphere.

a)

A

b)

B

c)

C

d)

D

129.

A person on Pluto’s surface would experience a(n)_______________gravitational force compared to being on Earth.

a)

weaker, because Pluto is further from the sun

b)

weaker, because Pluto has less mass

c)

equal, because both planets orbit the sun

d)

stronger, because Pluto has a more elliptical orbit

130.

Does an earth-orbiting satellite or the moon experience a greater force of gravity from the Earth?

a)

The satellite, because it is much closer to the earth.

b)

The moon, because it is much more massive.

c)

They experience the same force, because they both orbit the earth.

d)

Neither experiences a force, because they are in space.

131.

Which of the following statements is correct about weight and mass?

a)

Mass and weight both vary with location.

b)

Mass varies with location, but weight does not.

c)

Weight varies with location, but mass does not.

d)

Neither mass nor weight varies with location.

132.

Planets travel at _______________distances and speeds as they orbit the sun.

a)

the same

b)

different, faster when closer, slower when farther away

c)

different, slower when closer, faster when farther away

d)

the same distance but different speeds

133.

When the earth is closest to the sun, it is ____________ and when it is farthest from the sun it is____________.

a)

winter (January), summer (July)

b)

summer (July), winter (December)

c)

fall (September), spring (March)

d)

spring (April), summer (June)

134.

Which of the graphs shows how the force on an object changes if the mass increases and the gravitational acceleration stays constant?

a)

A

b)

B

c)

C

d)

D

135.

Two balls are dropped at the same height. One ball is dropped from table height and the other initially moves horizontally across the table and then falls off the edge, as shown in the figure. If both balls are dropped at exactly the same time, which one will hit the ground first?

a)

Ball A because it has the shortest distance to travel.

b)

Ball B because it is already travelling downward.

c)

A and B hit at same time because gravity pulls all objects the same.

136.

In a heliocentric system, Earth revolves around

a)

Mars

b)

The moon

c)

Stars

d)

The sun

137.

The fact that each planet’s orbit is an ellipse was discovered by

a)

Copernicus

b)

Kepler

c)

Galileo

d)

Brahe

138.

What shape are the orbits of most comets?

a)

long narrow ellipses

b)

nearly circular ellipses

c)

circles

d)

spherical

139.

Copernicus explained that

a)

the sun is at the center of the system of planets.

b)

the sun and the planets revolve around Earth.

c)

the geocentric system is correct.

d)

there are only six planets.