Navigate
to Answers for:
[ Questions #1-#14 | Questions #15-#28 | Questions #29-#40 ] |

1. Which of the following statements are true of an object moving in a circle at a constant speed? Include all that apply.

- The object experiences a force which has a component directed parallel to the direction of motion.
- Inertia causes objects to move in a circle.
- There can be a force pushing outwards on the object as long as the net force in inwards.
- Because the speed is constant, the acceleration is zero.
- The acceleration and the net force vector are directed perpendicular to each other.
- If the net force acting upon the object is suddenly reduced to zero, then the object would suddenly depart from its circular path and travel tangent to the circle.
- The acceleration of the object is directed tangent to the circle.

##
Useful
Web Links |

Speed and Velocity || Acceleration || The Centripetal Force Requirement |

For Questions
#2-#5, identify the type of force which causes
the
following **bold-faced** objects to travel along a
circular
path.

2. An **eraser**
is tied to a string swung in a
horizontal circle.

a. gravity |
b. normal |
c. tension |
d. applied |

e. friction |
f. spring |
g. electrical |
h. magnetic |

a. gravity |
b. normal |
c. tension |
d. applied |

e. friction |
f. spring |
g. electrical |
h. magnetic |

4. A **car**
makes a sharp right-hand turn along
a level roadway.

a. gravity |
b. normal |
c. tension |
d. applied |

e. friction |
f. spring |
g. electrical |
h. magnetic |

5. A **roller
coaster car** passes through a
loop. Consider the car at the bottom of the loop.

a. gravity |
b. normal |
c. tension |
d. applied |

e. friction |
f. spring |
g. electrical |
h. magnetic |

##
Useful
Web Links |

For Questions #2-#5:The Centripetal Force Requirement |

6. A physics teacher ties an eraser to the end of a string and then whirls it in a counter-clockwise circle. If the teacher lets go of the string, then the eraser hits a student (or several students) in the classroom. If the string is let go when the eraser is at point X on the diagram at the right, then which student(s) in the class will the eraser hit? Write the initials in this space: ________________

##
Useful
Web Links |

Speed and Velocity |

7. Which of the following statements are true about gravitational force? Identify all that apply.

- The gravitational force only acts between very, very massive objects.
- The gravitational force between an object and the earth is inversely related to the distance between the object's and the earth's center.
- The gravitational force can ALWAYS be accurately calculated by multiplying the object mass by the acceleration of gravity (m•g).
- The gravitational force acting upon an object is the same as the weight of the object.
- The gravitational force between two objects is independent of the mass of the smaller of the two objects.
- If object A gravitationally attracts object B with a force of X Newtons, then object B will also gravitationally attract object A with the same force of X Newtons.
- The doubling of the separation distance (measured from the center) between two objects will halve the gravitational force between the objects.
- It an object is placed two earth-radii above the surface of the earth, then the force of gravitational attraction between the object and the earth will be one-fourth the magnitude as on earth's surface.
- Orbiting astronauts do not experience a force of gravity; this explains why they feel weightless.

##
Useful
Web Links |

Newton's Law of Universal Gravitation |

8. Which of the following statements are true about the acceleration of gravity? Identify all that apply.

- The acceleration of gravity experienced by objects located near to (and far from) from the earth depends upon the mass of the object.
- The acceleration of gravity experienced by objects located near to (and far from) from the earth depends upon the mass of the Earth.
- The acceleration of gravity experienced by objects located near to (and far from) the earth is inversely related to the distance between the center of the object and the center of the earth.
- Increasing the mass of an object will increase the acceleration of gravity experienced by the object.
- Doubling the distance between an object and the earth's center will decrease the acceleration of gravity by a factor of four.
- The acceleration of an orbiting satellite is equal to the acceleration of gravity at that particular location.
- If the mass of the Earth were doubled (without an
alteration in its radius), then the acceleration of gravity on its
surface would be approximately 20 m/s
^{2}. - If the mass of the Earth were doubled and the radius of the
earth were doubled, then the two changes would offset each other and
the acceleration of gravity on its surface would still be approximately
10 m/s
^{2}.

##
Useful
Web Links |

The Value of g |

9. Which of the following statements are true about satellites? Identify all that apply.

- Satellites are falling projectiles.
- All satellites follow circular paths.
- The orbital velocity required of a satellite is dependent upon the mass of the satellite; a more massive satellite would require a greater orbital speed.
- The orbital velocity of a satellite does not depend upon the mass of the planet around which it orbits.
- A
*high-altitude*satellite will require a greater orbital speed than a*low-altitude*satellite. - By definition, a geosynchronous satellite orbits the earth in a perfect circle, maintaining the same distance above the surface of the earth.
- Satellites travel faster along their orbital path when they are closest to the earth.
- The acceleration of a satellite varies inversely with its distance from the center of the earth. More distant satellites have smaller accelerations.

##
Useful
Web Links |

Circular Motion Principles for Satellites || Mathematics of Satellite Motion |

10. Which of the following statements are true about the motion of planets about the sun? Identify all that apply.

- The force of gravity is the only force which acts upon the planets.
- Their trajectories are highly elliptical.
- The planets which are furthest from the sun have the greatest period.
- For any given planet, the speed is greatest when the planet is closest to the sun.
- The velocity vector is directed tangent to the elliptical path.
- The net force vector is at all times directed perpendicular to the velocity vector.
- To keep the planet from escaping the sun's gravitational field, the net force vector is greatest when the planet is furthest from the sun.

##
Useful
Web Links |

Kepler's Three Laws || Circular Motion Principles for Satellites || Mathematics of Satellite Motion |

11. Explain how something can be moving at a constant speed yet be accelerating at the same time.

##
Useful
Web Links |

Acceleration |

12. How did Newton come up with the idea that the moon is actually "falling" toward the Earth.

##
Useful
Web Links |

The Apple, the Moon, and the Inverse Square Law |

13. Distinguish between true- and apparent-weightlessness.

##
Useful
Web Links |

Weightlessness |

14. Describe the apparent weight of a person in an elevator while upward, accelerating downward, and not accelerating.

##
Useful
Web Links |

Weightlessness |

15. In the diagram at the right, draw vector arrows (straight lines with arrowheads) which indicate the following for an object which is moving in a clockwise circle.

- the net force at point A.
- the acceleration at point B.
- the velocity at point C.

##
Useful
Web Links |

Speed and Velocity || Acceleration || The Centripetal Force Requirement |

16. The diagram at the right shows a satellite orbiting the Earth in an elliptical path in a clockwise direction.

- Draw a vector representing the velocity of the object at position A.
- raw a vector representing the force on the object at position D.
- Draw a vector representing the acceleration of the object at position C.
- At which of the four positions is the satellite moving fastest?

##
Useful
Web Links |

Circular Motion Principles for Satellites || Mathematics of Satellite Motion |

17. A 1.20-kg bucket is held by a string and whirled in a vertical circle. The radius of the circle is 1.30 m. The speed of the bucket is 3.70 m/s at the top of the loop and 7.10 m/s at the bottom of the loop. On the diagrams below, construct a free-body diagram (label all forces according to type) for the bucket at both the top and the bottom of the loop. Fill in the blanks and clearly indicate the magnitude of the individual force values on your free-body diagram.

##
Useful
Web Links |

Newton's Second Law - Revisited |

18. Construct a free-body diagram showing the direction and types of forces acting upon the car at the top and the bottom of a loop. Be sure to label the forces according to type.

Anna experiences a downward acceleration of 24.0 m/s^{2}
at the top of the loop and an upwards acceleration of 12.0
m/s^{2} at the bottom of the loop. Use Newton's
second law to
fill in all the blanks and to ultimately determine the normal force
acting upon Anna's 800. kg roller coaster car. **PSYW**

Top |
Bottom |

_{net }= _______________ |
_{net }= _______________ |

_{grav }= _______________ |
_{grav }= _______________ |

_{norm }= _______________ |
_{norm }= _______________ |

##
Useful
Web Links |

Roller Coasters and Amusement Park Physics |

19.
A fullback is running a sweep around the left side of the line. As he
rounds the turn, he is momentarily moving in circular motion,
sweeping out a quarter-circle with a radius of 4.17 meters. If the
83.5-kg fullback makes the turn with a speed of 5.21 m/s, then what
is his acceleration, the net force, the angle of lean (measured to
the vertical), and the total contact force with the ground?
**PSYW**

a = ____________F

_{net}= ____________F

_{grav}= ____________F

_{norm}= ____________F

_{frict}= ____________F

_{contact}= ____________Angle of Lean = ____________

##
Useful
Web Links |

Athletics |

20. Pete Zaria is riding the Cliff Hanger at Great America. Pete enters a
cylindrical barrel which makes 18.5 revolutions every minute. The
diameter of the barrel is 6.92 m. Pete's mass is 64.7 kg. Construct a
free-body diagram showing the forces acting upon Pete. Calculate the
acceleration and net force acting upon Pete Zaria. Finally, determine
the coefficient of friction between Pete and the walls that would be required to support Pete's weight.
**PSYW**

##
Useful
Web Links |

Roller Coasters and Amusement Park Physics |

21. Two objects attract
each other with a force of
gravity (F_{grav}) of 36 N. If the distance
separating the
objects is doubled, then what is the new force of gravitational
attraction? **PSYW**

22. Two objects attract
each other with a force of
gravity (F_{grav}) of 36 N. If the distance
separating the
objects is doubled and the masses one of the objects is tripled, then
what is the new force of gravitational attraction? **PSYW**

23. Two objects attract
each other with a force of
gravity (F_{grav}) of 36 N. If the distance
separating the
objects is increased by a factor of 4 and the masses of both objects
are tripled, then what is the new force of gravitational attraction?
**PSYW**

##
Useful
Web Links |

24. Suppose that the acceleration of gravity on the surface of planet X is 12 m/s/s. Determine the acceleration of gravity at a location ...

- of 2 radii from the center of planet X.
- of 4 radii from the center of planet X.
- of 2 radii from the surface of planet X.
- on the surface of planet X if the planet mass were twice as large (same radius).
- on the surface of planet X if the planet mass were one-half as large (same radius).

##
Useful
Web Links |

The Value of g |

25. Suppose that a planet
was located 12.0 times
further from the sun than the earth's distance from the sun.
Determine the period of the planet. **PSYW**

##
Useful
Web Links |

Kepler's Three Laws |

26. The acceleration of
gravity on the moon is
approximately one-sixth the value on earth's surface. If a person
weighs 60.0 N on the moon's surface, what is his/her approximate mass
on Earth? **PSYW**

##
Useful
Web Links |

The Value of g |

27. Determine the force of
gravitational attraction
between a 52.0-kg mother and a 3.0-kg child if their separation distance
is 0.50 meters. **PSYW**

##
Useful
Web Links |

Newton's Law of Universal Gravitation |

28. Use the following
information to determine the
orbital velocity at *treetop level* on the surface of
the moon.
**PSYW**

Mass of moon = 7.36
x 10^{22} kg

Radius of Moon = 1.74 x 10^{6 }m

Radius of Moon = 1.74 x 10

##
Useful
Web Links |

Mathematics of Satellite Motion |

29. A roller coaster car loaded with passengers, has a mass of 500. kg; the radius of curvature of the track at the bottom point of a dip is 12.0 m. The vehicle has a speed of 18.0 m/s at this point.

- In the space below, draw a free-body diagram for the car (label forces according to type).
- Calculate the acceleration and the net force acting upon
the car.
**PSYW** - Calculate the force exerted on the vehicle by the track?
**PSYW**

##
Useful
Web Links |

Roller Coasters and Amusement Park Physics |

30. What is the acceleration of a piece of dust on an old-fashioned record album, 15 cm from the center, if the record is spinning at 33.3 rpm?

##
Useful
Web Links |

Mathematics of Circular Motion |

31. What is the tension in a 0.500 meter rope which carries a 2.50 kg bucket of water in a vertical circle with a velocity of 3.00 m/s when the bucket is at the bottom of its swing?

##
Useful
Web Links |

Newton's Second Law - Revisited |

32. A 53.5-kg rider on a roller coaster car is moving 10.3 m/s at the top of a loop which has a radius of curvature of 7.29 m. Determine the normal force experienced by the rider.

##
Useful
Web Links |

Roller Coasters and Amusement Park Physics |

33. Determine the minimum coefficient of friction required to keep a 920.-kg car on a turn with a radius of 26.8 m. The car is traveling 29.9 m/s and the roadway is level.

##
Useful
Web Links |

Newton's Second Law - Revisited |

34. With what speed (in mi/hr) must you drive your car across the crest of a hill of radius 37.1-m in order to feel weightless (1.00 m/s = 2.24 mi/hr)?

##
Useful
Web Links |

Newton's Second law - Revisited || Weightlessness |

35. What is the reading of
a bathroom scale when a
man of mass 72 kg stands on it while riding in an elevator
accelerating upwards at 5.4 m/s^{2}?

##
Useful
Web Links |

Weightlessness |

36. An airplane pilot makes a vertical loop with a 56-2-m radius. Determine the normal force acting upon the pilot's 62.6-kg body at the top of the loop if his air speed is 64.1 m/s.

##
Useful
Web Links |

Newton's Second law - Revisited |

37. Use the following information to help determine the acceleration of the planet Pluto about the sun.

Mass of Sun = 1.991
x 10^{30} kg

Sun-Pluto Distance = 5.91 x 10^{12 }m

Sun-Pluto Distance = 5.91 x 10

##
Useful
Web Links |

The Value of g |

38. What is the period of
rotation of Venus in
earth years if it is a distance of 1.08 x 10^{11}
meters from
the sun? (The earth-sun distance is 1.5 x 10^{11}
m.)

##
Useful
Web Links |

Kepler's Three Laws |

39. What is the
gravitational attraction between
the proton and electron in an Hydrogen atom if they are 5.3 x
10^{-11} meters apart? (m_{proton}
= 1.67 x
10^{-27} kg; m_{electron} =
9.11x10^{-31}
kg)

##
Useful
Web Links |

Newton's Law of Universal Gravitation |

40. Use the following information to help determine the orbital velocity and orbital period of a satellite at a location of 15000 miles above the surface of the earth.

Mass of Earth = 5.98
x 10^{24} kg

Radius of Earth = 6.37 x 10^{6 }m

1609 m = 1.00 mi

Radius of Earth = 6.37 x 10

1609 m = 1.00 mi

##
Useful
Web Links |

Mathematics of Satellite Motion |

Navigate
to Answers for:
[ Questions #1-#14 | Questions #15-#28 | Questions #29-#40 ] |

GBS Physics Home Page || ChemPhys 173 Home Page || The Physics Classroom The Laboratory || Unit Schedules || The Review Session || The Quiz Room |