Deck 5: Gravity and Motion

Question 1

If the diameter of the Earth were suddenly reduced to one-fourth of its present size while its mass remained the same,how would your weight be altered?

A)It would become 4 times as great
B)It would become 16 times as great
C)It would become 8 times as great
D)It would remain unchanged

Answer 1

It would become 16 times as great

Question 2

A hockey puck is seen moving north over a frozen pond at a speed of 2m/sec.A while later it is seen moving west at 2m/sec.Which of the following correctly describes the forces acting on the puck?

A)A force has acted,since the direction has changed
B)No force has acted,since the speed is the same
C)A force has acted,but only in a northward direction
D)The above information is insufficient to tell if forces have acted

Answer 2

A force has acted,since the direction has changed

Question 3

What happens to the angular momentum of a planet as it orbits the Sun?

A)It increases steadily with time
B)It gradually drops to zero
C)It increases and decreases as the planet changes speed
D)It remains constant

Answer 3

It remains constant

Question 4

For an object to accelerate it must change its

A)Speed
B)Direction of motion
C)Speed and direction of motion
D)Speed or direction of motion

Question 5

Suppose an astronaut whose mass is 50 kg pushes herself away from an artificial satellite that has a mass of 500 kg.While she is pushing,the acceleration of the satellite is 1 m/s per second.What is the acceleration of the astronaut?

A)1 m/s per second
B)10 m/s per second
C)1/10 m/s per second
D)100 m/s per second

Question 6

A mass of 50 kg is acted on by a force of 200 N.The motion of the object subsequently will be

A)Motion at a constant speed of 0.25 m/sec
B)Acceleration at a rate of 4 m/sec/sec
C)Acceleration at a rate of 200 m/sec/sec
D)Motion at a constant speed of 50 m/sec

Question 7

How will an object move if there are no forces acting on it?

A)With constant acceleration
B)In a straight line at constant speed
C)On an ellipse
D)It can't move at all if no forces are present

Question 8

Which of the following bodies is accelerating?

A)A body moving in a straight line at constant speed
B)A body at rest
C)A body moving in a circle at constant speed
D)A body with no forces acting on it

Question 9

The force required to keep an object in a circular orbit is directed

A)Away from the center of the circle
B)In the direction in which the object is moving
C)In the direction opposite to that in which the object is moving
D)Toward the center of the circle

Question 10

Suppose an object moves in a circular path at constant speed.What can be said about the force acting on it?

A)There is no force acting on it
B)The force acting on it must constantly vary in strength
C)The force acting on it must vary in direction.
D)The force acting on it must be gravity.

Question 11

What is always true when an object accelerates?

A)It speeds up
B)It changes direction
C)A force is acting on it
D)Its mass changes

Question 12

If the distance between two objects is doubled,the force of gravity they exert on each other will

A)Double
B)Become 1/2 as large
C)Become 1/4 as large
D)Remain the same

Question 13

If the masses of the Sun and Earth each were doubled,the force of gravity between them would

A)Remain the same
B)Double
C)Become 4 times as large
D)Become 16 times as large

Question 14

An object speeds up in such a way that its acceleration is constant.What can we say about the force acting on the object?

A)There is no force acting on it
B)The force acting on it is constant
C)The force acting on it increases steadily
D)The force acting on it decreases steadily

Question 15

Suppose an artificial satellite is in a circular orbit about the Earth.What can be said about the acceleration of the satellite?

A)Its acceleration is zero
B)It is accelerating because its speed changes constantly
C)It is accelerating because its direction changes constantly
D)We can tell if it is accelerating only if we can measure the force on it

Question 16

Suppose the Earth were moved to Mercury's distance from the Sun (0.4 AU).How would the gravitational force between the Earth and Sun then compare to its present value?

A)It would be the same
B)It would be about 2.5 times as strong
C)It would be about 6 times as strong
D)It would be about 0.4 times as strong

Question 17

When a force is applied to a body with a mass of 100 kg,the acceleration of the body is 1 m/s/s.If the same force is applied to a body with a mass of 40 kg,what is the acceleration of the body?

A)0.25 m/s/s
B)1 m/s/s
C)10 m/s/s
D)2.5 m/s/s

Question 18

Compared with your mass on Earth,your mass on the Moon would be

A)About 6 times more
B)About 6 times less
C)About 36 times more
D)About 36 times less
E)Exactly the same

Question 19

The radius of the Moon is one-fourth that of the Earth,and its mass is 1.3 percent of the Earth's mass.If you were standing on the surface of the Moon,what would your weight be?

A)20% of Earth weight
B)50% of Earth weight
C)2% of Earth weight
D)200% of Earth weight

Question 20

What is centripetal force?

A)The force required to keep an object moving in a circular path
B)The gravitational force between two objects
C)The force needed to keep an object moving at constant velocity
D)The force that pushes an object outward as it moves in a circular path

Question 21

Why does the Earth have a tidal bulge on the side opposite the Moon?

A)Lunar gravity is weakest there
B)There is another object pulling on the Earth in that direction
C)The Earth rotates fastest on that side
D)That is where the Moon's repulsive force is strongest

Question 22

Suppose there is a planetary system in which a planet with an average distance of 3 AU from the star has an orbital period of 3 years.What is the mass of the star?

A)1 solar mass
B)3 solar masses
C)9 solar masses
D)27 solar masses

Question 23

During spring tides

A)The Earth,Moon,and Sun are all aligned.
B)The Moon,Earth,and Sun are all at right angles
C)Only the Earth is deformed,not the Moon
D)Day and night are the same interval of time
E)There is a good chance of a major earthquake

Question 24

Suppose the escape velocity of Planet A is 10 km/s.What would be the escape velocity of a Planet B,which is twice as massive and has the same size as Planet A?

A)7 km/s
B)10 km/s
C)14 km/s
D)20 km/s

Question 25

The mass of an object _____________ from a planet or star.

A)increases with increasing distance
B)decreases inversely with increasing distance
C)stays the same with increasing distance
D)decreases inversely with the square of the distance

Question 26

A comet has a speed that is slightly larger than escape velocity.What path around the Sun will the comet follow?

A)A circle
B)An ellipse
C)A parabola
D)A hyperbola

Question 27

Assume that Saturn is 10 times as far from the Sun as the Earth is,and that it has 100 times the mass of the Earth.The gravitational force between Saturn and the Sun is

A)100 times the force between the Earth and Sun
B)10 times the force between the Earth and Sun
C)Equal to the force between the Earth and Sun
D)1/10 the force between the Earth and Sun
E)1/100 the force between the Earth and Sun

Question 28

The tidal variations are largest during the _____________.

A)fall and spring
B)new and full phases
C)first and third quarter phases
D)summer and winter

Question 29

If the Earth were orbiting a ten solar mass star,at a distance of 1 astronomical unit,how would its orbital period be affected?

A)It would be unchanged
B)It would be about 1/3 of a year
C)It would be about 3 years
D)It would be about 1/10 of a year

Question 30

Where are the greatest tidal forces encountered?

A)Near large,massive objects
B)Near small,massive objects
C)Near large,rapidly moving objects
D)Near small,rapidly moving objects

Question 31

The force of gravity between two objects has what dependence on the distance between the objects?

A)Force is directly proportional to the distance
B)Force is inversely proportional to the distance.
C)Force is proportional to the square of the distance.
D)Force is inversely proportional to the square of the distance.

Question 32

The tides are the smallest during what lunar phase?

A)Third quarter
B)First quarter
C)Full Moon
D)more than one of the above

Question 33

Suppose the Moon's mass were 4 times as large and it were twice as far from the Earth? How would these changes affect the force of gravity between the earth and the Moon?

A)It would double
B)It would decrease by a factor of 4
C)It would be the same
D)It would decrease by a factor of 8