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UCM&ULG Exam

Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 1. 

What is the direction of the force that acts on clothes in the spin cycle of a washing machine?
a.
Inward
b.
Down
c.
Outward
d.
Up
 

 2. 

A tin can whirled on the end of a string moves in a circle because
a.
the can continually pulls on the string.
b.
once the can starts moving, that is its natural tendency.
c.
there is a force on the can pulling it outward.
d.
there is an inward force acting on the can.
e.
all of the above
 

 3. 

If you whirl a tin can on the end of a string and the string suddenly breaks, the can will
a.
fly directly away from you.
b.
fly off, tangent to its circular path.
c.
fly directly toward you.
d.
spiral in toward your hand.
e.
spiral away from your hand.
 

 4. 

A ladybug rests on the bottom of a tin can that is being whirled horizontally on the end of a string. Since the ladybug, like the can, moves in a circle, there must be a force on it. What exerts this force?  (This question pertains to the ladybug!)
a.
Gravity
b.
The string
c.
There is no force acting on it.
d.
The bottom of the can
e.
Your hand
 

 5. 

People in the future may well live inside a rotating space structure that is more than 2 km in diameter. Inside the structure, people on the inside of the outer edge will experience 1 g while people halfway to the axis will experience
a.
2 g.
b.
1 g.
c.
mc005-1.jpg g.
d.
mc005-2.jpg g.
e.
0 g.
 

 6. 

"Centrifugal forces" are an “apparent reality” to observers that are
a.
rotating.
b.
an inertial reference frame.
c.
moving at constant velocity.
d.
at rest.
e.
none of the above
 

 7. 

As the rotational speed of a space habitat increases, the “perceived weight” of people inside
a.
decreases.
b.
increases.
c.
stays the same.
 

 8. 

A car travels in a circle with constant speed. The net force on the car
a.
is zero because the car is not accelerating.
b.
is directed forward, in the direction of travel.
c.
is directed toward the center of the curve.
d.
none of the above
 

 9. 

Suzie Spacewalker hovers in space beside a space station. Both she and the center of mass of the space station are at relative rest. If the space station is in Earth orbit, then Suzie
a.
is also in Earth orbit.
b.
is not in Earth orbit.
c.
may or may not be in Earth orbit.
 

 10. 

People knew things about the moon already, but Newton had the insight to see that the _____.
a.
moon is moving
b.
moon orbits Earth
c.
force on the moon has the same nature as the force on an apple
d.
moon always keeps one side toward Earth
e.
none of the above
 

 11. 

Newton hypothesized that the moon _____.
a.
moves like a projectile
b.
is falling around Earth
c.
has tangential velocity that prevents it from falling into Earth
d.
is actually attracted to Earth
e.
all of the above
 

 12. 

Newton reasoned that the gravitational attraction between Earth and the moon must be _____.
a.
reduced by distance
b.
independent of distance
c.
directly proportional to distance
d.
the same at all distances
e.
all of the above
 

 13. 

If the mass of Earth increased, with no change in radius, your weight would _____.
a.
stay the same
b.
decrease
c.
increase also
 

 14. 

If the radius of Earth decreased, with no change in mass, your weight would _____.
a.
not change
b.
increase
c.
decrease
 

 15. 

If Earth's mass decreased to one half its original mass, with no change in radius, then your weight would _____.
a.
stay the same
b.
decrease to one half your original weight
c.
decrease to one quarter your original weight
d.
none of the above
 

 16. 

The gravitational force between two massive spheres
a.
is always an attraction.
b.
depends on how massive they are.
c.
depends inversely on the square of the distances between them.
d.
all of the above
 

 17. 

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 B
b.
The force on A
c.
Both forces are the same.
 

 18. 

Two objects move toward each other because of gravitational attraction. As the objects get closer and closer, the force between them _____.
a.
remains constant
b.
decreases
c.
increases
 

 19. 

Gravitational forces are the weakest forces found in nature. Because of this _____.
a.
the gravitational effect between a pencil and Earth cannot be seen
b.
there is no gravitational force between two 1-kg masses
c.
gravitational forces that are easily observed involve one or more large masses
d.
there is no movement between two 1-kg masses located near each other in space
e.
gravitational effects occur only when a large mass is involved
 

 20. 

Suppose the gravitational force between two massive spheres is 100 N. If the distance between the spheres is doubled, what is the force between the masses?
a.
400 N
b.
200 N
c.
100 N
d.
50 N
e.
25 N
 

 21. 

The force of gravity acting on you will increase if you _____.
a.
stand on a planet with a radius that is shrinking
b.
burrow deep inside the planet
c.
both A and B
d.
none of the above
 

 22. 

The force of gravity on you is greatest when you are standing _____.
a.
far above Earth's surface
b.
just above Earth's surface
c.
on Earth's surface
 

 23. 

The reason the moon does not fall into Earth is that _____.
a.
Earth's gravitational field at the moon is weak
b.
the moon has a sufficiently large tangential speed
c.
gravitational pull of other planets keeps the moon up
d.
the moon has less mass than Earth
e.
none of the above
 

 24. 

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 low altitude and sell at a high altitude
b.
disregard altitude because it has a negligible effect
c.
buy at a high altitude and sell at a low altitude
 

 25. 

A planet has half the mass of the Earth and half the radius. Compared to its weight on Earth, an apple on this planet would weigh _____.
a.
twice as much
b.
one-fourth as much
c.
half as much
d.
the same
e.
zero
 

 26. 

Consider the gravitational force between 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
 

 27. 

Which is greater, the gravitational force between Earth and the moon, or the force between Earth and the sun?
a.
Earth–moon
b.
equal
c.
Earth–sun
 

 28. 

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.
high density
b.
greater distance from the sun
c.
large radius
 

 29. 

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.
one-eighth its normal value
b.
one-quarter its normal value
c.
half its normal value
d.
none of the above
 

 30. 

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
 

 31. 

Since Earth is attracted to the sun, why doesn't it fall into the sun?
a.
Because it has too much mass to move toward the sun
b.
Because it has sufficient tangential velocity
c.
Because there is an equal force holding it away from the sun
d.
Because it has too much inertia to move toward the sun
e.
all of the above
 

 32. 

A 560-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.
140 N
c.
280 N
d.
560 N
e.
none of the above
 

 33. 

Suppose the gravitational force between two masses is 70 N. If the magnitude of one of the masses halves, what is the force between the masses?
a.
280 N
b.
140 N
c.
70 N
d.
35 N
e.
18 N
 

 34. 

Suppose the gravitational force between two spheres is 70 N. If the distance between the spheres is halved, what is the force between the masses?
a.
17.5 N
b.
35 N
c.
70 N
d.
140 N
e.
280 N
 

 35. 

Suppose the gravitational force between two spheres is 30 N. If the magnitude of each mass doubles, what is the force between the masses?
a.
8 N
b.
15 N
c.
30 N
d.
60 N
e.
120 N
 

 36. 

If a car with a mass of 200Kg turns a 20m radius turn at 3m/s, what will the Centripetal Force be?
a.
180N
c.
45N
b.
90N
d.
200N
 

 37. 

If a 200Kg car wants to make a 10m radius turn safely, it must negotiate the turn with no more than 2000N.  What is the maximum velocity that will allow it to do so?
a.
20 m/s
c.
10 m/s
b.
5 m/s
d.
15 m/s
 

True/False
Indicate whether the statement is true or false.
 

 38. 

Any force that causes an object to move in a circular path is called a centripetal force.
 

 39. 

It is possible to rotate a very large cylindrical space habitat around its central axis at just the right speed so people living inside the cylinder will experience a force that feels like gravity.
 

 40. 

A bug on a turning phonograph record will make more turns per minute if it is located toward the center of the record.
 

 41. 

Ladybugs on the inside of a spinning bicycle tire can experience a force that feels like gravity to them.
 

 42. 

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

 43. 

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.
 

 44. 

The gravitational force of Earth on an object does not depend upon the object’s mass.
 

 45. 

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

 46. 

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

 47. 

Because Earth is "falling" around the sun, it will eventually crash into it.
 

 48. 

Because Earth and moon are gravitationally attracted toward each other, they will soon collide.
 

 49. 

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

 50. 

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

Essay
 

 51. 

Explain what a centripetal force is and give some examples. Are centripetal forces real?
 

 52. 

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?
 

 53. 

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.
 

Problem
 

 54. 

The tangential speed at the outer rim of a Ferris wheel is 10 m/s. What is the tangential speed of a position half way from the center to the outer rim?
 

 55. 

By what factor would your weight be multiplied if Earth's diameter were 2 times as big and Earth's mass remained unchanged?
 



 
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