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Calendar

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

1)Which has greater linear speed, a horse near the outside rail of a merry-go-round or a horse near the inside rail?

A) The outside horse
B) The inside horse
C) Neither ¹ they both have the same linear speed.

2) Which has greater angular speed, a horse near the outside rail of a merry-go-round or a horse near the inside rail?

A) The outside horse
B) The inside horse
C) Neither ¹ they both have the same angular speed.

3) Which of the following is NOT a unit of rotational speed?

A) Revolutions per second
B) Rotations per second
C) Revolutions per minute
D) Meters per second
E) Rotations per minute

4) What is the direction of the force that acts on clothes in the spin cycle of a washing machine?

A) Outward
B) Inward
C) Up
D) Down

5) A tin can whirled on the end of a string moves in a circle because __________.

A) once the can starts moving, that is its natural tendency.
B) the can continually pulls on the string.
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

6) 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 directly toward you.
C) fly off, tangent to its circular path.
D) spiral away from your hand.
E) spiral in toward your hand.

7) 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?

A)Your hand
B)The string
C)The can
D)Gravity
E)Nonsense. There is no force acting on it.

8) 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)1/2 g.
D)1/4 g.
E)0 g.

9) "Centrifugal forces" are an apparent reality to observers in a reference frame that is __________.

A)moving at constant velocity.
B)an inertial reference frame.
C)at rest.
D)rotating.
E)none of the above

10) A person weighs less at the equator than at the poles. The reason for this has to do with the __________.

A)spin of the earth.
B)tidal bulges.
C)higher temperature at the equator, and expansion of matter.
D)influence of the sun, moon, and all the planets.
E)none of the above

11) As the rotational speed of a space habitat increases, the weight of people inside __________.

A)increases.
B)decreases.
C)stays the same.

12) A car travels in a circle with constant speed. The net force on the car __________.

A)is directed forward, in the direction of travel.
B)is directed toward the center of the curve.
C)is zero because the car is not accelerating.
D)none of the above

13) If the earth rotated more slowly about its axis, your weight would __________.

A)increase.
B)decease.
C)stay the same.

14) To weigh less in the Northern Hemisphere, you should go __________.

A)north.
B)south.
C)east.
D)west.

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

15) A possible space habitat of the future is a cylinder in space rotating about its long axis. What is the relative gravitational field along the axis of the habitat?

A)Zero
B)g
C)One-quarter g
D)One-half g
E)Three-quarters g

16) When a railroad train rounds a banked track, the centripetal force needed comes not from friction, but from the __________.

A)normal force.
B)horizontal component of the normal force.
C)vertical component of the normal force.
D)none of the above

17) The centripetal force exerted on stunt motorcyclist Biker Bob while riding on the inner vertical surface of a circular track is  __________.

A)his weight.
B)friction.
C)the normal force.
D)none of the above

18) Nellie Newton swings a rock into a circular path while holding an attached string overhead. The string makes a 45 degree angle to the vertical (comprising a "conical pendulum").  The centripetal force that holds the rock in its circular path is the __________.

A)tension in the string.
B)horizontal component of the string tension.
C)vertical component of the string tension.
D)none of the above

19) Stunt motorcyclist Biker Bob rides his bike inside a futuristic rotating space station-a giant rotating donut-shaped structure in space. The normal support force feels like weight to him. As he rides his bike in the same direction that the station rotates, the normal force __________.

A)increases.
B)decreases.
C)remains unaffected.

20) Stunt motorcyclist Biker Bob rides his bike inside a futuristic rotating space station-a giant rotating donut-shaped structure in space. The normal support force feels like weight to him. As he rides his bike in the opposite direction that the station rotates, the normal force __________.

A)increases.
B)decreases.
C)remains unaffected.

21) Suzie Spacewalker hovers in space beside a rotating space station in outer space. 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 is __________.

A)also in earth orbit.
B)may or may not be in earth orbit.
C)not in earth orbit.

22) A space habitat is designed so that the variation in g between a person's head and feet is less than  0.01 g. If the person is  2 m tall, then the radius of the habitat is __________.

A)20 m.
B)200 m.
C)2000 m.
D)more than 2000 m.

23) A swimming area in a rotating space habitat is located in a  one-fourth-g region. If a diver can jump  1 m high in a  1-g region, how high can the same diver jump in the swimming area?

A)1 m
B)2 m
C)4 m
D)16 m
E)More than 16 m

Write True or False in the space provided.

24) A straight line about which rotation takes place is called an axis.

25) The rotational speed of a wheel is defined as the number of rotations it makes in a  10-second interval.

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

27) 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.

28) The only reason riders on a rotating platform in a carnival ride don't fall out is because they are strapped in.

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

30) When you whirl a can on the end of a string, the centripetal force on the can is actually the pull of the string on the can.

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

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

32) Discuss the difference between linear speed and rotational speed.  Where does a ladybug sitting on a rotating record have the greatest linear speed? The greatest rotational speed? What kind of speed would she have at the center?

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

34) A girl sits on the inside of the outer edge of a rotating space habitat. What forces act on her? Later she climbs an artificial mountain inside the habitat and gets very close to the rotational axis. How would her "weight" change on her climb?

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

35) The tangential speed at the outer rim of a Ferris wheel is  8 m/s. What is the tangential speed of a position half way from the center to the outer rim?

36) You sit at the outer rim of a Ferris wheel that rotates at  8 revolutions per minute (RPM). What would your rotational speed be if you were instead clinging to a position half way from the center to the outer rim?

37) A vertical pole standing against a wall topples to the ground and the center of the pole has a speed of  15 m/s as it hits. With what speed does the far end of the pole hit the ground?

38) Tapered rims on railroad-train wheels enable a train to round curves without any wheel skidding. Consider a curve where the outer track is one part in  100 longer than the inner track. The wide part of the rim should have a diameter wider than the narrow part by at least one part in ________.

39) At the outer edge of a rotating space habitat,  200 m from its center, the rotational acceleration is g. What is the rotational acceleration at a distance of  100 m from the center of the habitat?


If you have any questions, please email Ms. Cummings