Identify the choice that best completes the statement or answers the question. ____ 1. Which has greater linear speed, a horse near the outside rail of a merry-go-round or a horse near the inside rail?
The inside horse
The outside horse
Neither—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?
Neither—they both have the same angular speed.
The inside horse
The outside horse
____ 3. Which of the following is NOT a unit of rotational speed?
____ 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?
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
____ 17. The centripetal force exerted on stunt motorcyclist Biker Bob while riding on the inner vertical surface of a circular track is
the normal force.
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
vertical component of the string tension.
horizontal component of the string tension.
tension in the string.
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
____ 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 to the station’s rotation, the normal force
____ 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 also in Earth orbit.
is not in Earth orbit.
may or may not be 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
more than 2000 m.
____ 23. A game room in a rotating space habitat is located in a 0.25-g region. If a person can jump 0.5-m high in a 1-g region, how high can the same person jump in the game room?
More than 8 m
____ 24. Earth rotates and revolves through space. Earth rotates about the ______ , which is an ______ axis. Earth revolves about the ______, which is an _______ axis.
Indicate whether the statement is true or false. ____ 25. A straight line about which rotation takes place is called an axis.
____ 26. The rotational speed of a wheel is defined as the number of rotations it makes in a unit of time.
____ 27. Any force that causes an object to move in a circular path is called a centripetal force.
____ 28. 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.
____ 29. The only reason riders on a rotating platform in a carnival ride don't fall out is because they are strapped in.
____ 30. A bug on a turning phonograph record will make more turns per minute if it is located toward the center of the record.
____ 31. 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.
____ 32. Ladybugs on the inside of a spinning bicycle tire can experience a force that feels like gravity to them.
____ 33. When an object turns about an external axis, the motion is called rotation.
Essay - Choose one question to answer. Use complete sentences. 34. 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?
35. Explain what a centripetal force is and give some examples. Are centripetal forces real?
Problem 36. 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?
37. You sit at the outer rim of a Ferris wheel that rotates at 2 revolutions per minute (RPM). What would your rotational speed be if you were instead clinging to a position halfway from the center to the outer rim?
38. A vertical pole standing against a wall topples to the ground and the center of the pole has a speed of 13 m/s as it hits. With what speed does the far end of the pole hit the ground?
39. 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 50 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
40. At the outer edge of a rotating space habitat, 130 m from its center, the rotational acceleration is g. What is the rotational acceleration at a distance of 65 m from the center of the habitat?
CP Physics Chapter 10 Review
Answer Section MULTIPLE CHOICE 1. B
TRUE/FALSE 25. T
ESSAY 34. Linear speed is distance an object moves per unit time, whereas rotational speed is angle an object rotates per unit time. The ladybug will have the greatest linear speed at the edge of the record, but its rotational speed will be the same anywhere on the record. At the center of the record the ladybug has no linear speed, only rotational speed, as she rotates about her own and the record's axis.
35. A centripetal force is any force that makes an object move in a curved path. The gravitational force holding Earth in orbit about the sun is centripetal force. The electrical force holding an electron in orbit about the atomic nucleus is also centripetal force. The string tension that holds a rock whirling in a circular path at the end of a string is also a centripetal force. Centripetal forces are real forces because they are part of an interaction between two things.
PROBLEM 36. 5 m/s
37. 2 RPM
38. 26 m/s