Physics Quiz ROTATIONAL EQUILIBRIUM AND DYNAMICS

1. Physics Quiz ROTATIONAL EQUILIBRIUM AND DYNAMICS Each question is multiple choice. Select the best response to the question by pressing the button to the left of your choice. If your answer is correct, you will hear an applause. Use the forward and backward buttons at the lower corner of the slides to advance questions. Quiz by Dr. John Dayton

2. 1. What is the effect on an object of an unbalanced torque? A. The object will have a linear acceleration. B. The object will experience an angular acceleration. C. The object will begin to twist. D. The object will flex or bow. Quiz by Dr. John Dayton

3. 2. When is a torque produced? A. Whenever a force acts on an object. B. When a force acting on an object is directed at the axis of rotation. C. When a force acts on an object in conjunction with a moment arm. D. When the moment of inertia is acted on by a force. Quiz by Dr. John Dayton

4. 3. Define the term "line of action" of a force. A. the line along which a force acts or lies B. the axis of rotation of a rigid body C. the line connecting the pivot point and the point at which the force is acts D. the line between the pivot and the line along which the force acts Quiz by Dr. John Dayton

5. 4. What is a moment arm? A. The distance between the pivot and the point at which the force acts B. the perpendicular distance from the pivot to the line of action of a force C. the length of the object D. the length of the line of action Quiz by Dr. John Dayton

6. 5. A force acting on an object is decomposed into two components. The first component points from the point of application of the force directly toward the pivot point. The second component points perpendicular to the first. Which of these components is responsible for the torque produced? A. the first component pointing toward the pivot B. neither component if the force is decomposed C. the second, perpendicular, component D. both components contribute to the net torque Quiz by Dr. John Dayton

7. 6. What are the SI units of torque? A. J B. kg.m2 C. kg.m2/s D. N.m Quiz by Dr. John Dayton

8. 7. When an object is in rotational equilibrium, what condition must there be on the applied torques? A. all torques must be counter-clockwise B. their vector sum of all torques must be zero C. all torques must be clockwise D. all applied torques must be identically zero Quiz by Dr. John Dayton

9. 8. Real objects have both size and shape. Through what point does such an object`s weight act? A. the center of gravity B. the center of mass C. the pivot point D. the barrycenter Quiz by Dr. John Dayton

10. 9. A system of objects consists of a mass of 5 kg located at -2 m on the x-axis and another mass of 10 kg located at +4 m on the x-axis. Where is this system`s center of mass? A. +3 m on the x-axis B. at the origin C. +1 m on the x-axis D. +2 m on the x-axis Quiz by Dr. John Dayton

11. 10. Compare and contrast the concepts of the center of mass and the center of gravity. A. They are almost the same point for small objects. B. The center of gravity lies directly below the center of mass which is not dependent on gravity. C. If an asymmetric object is turned, its center of gravity changes position but its center of mass is the same. D. All of the above are true. Quiz by Dr. John Dayton

12. 11. What is moment of inertia? A. A temporary increase in effective mass caused by excessive acceleration. B. An additional amount of mass that has to be accounted for due to energy of rotation. C. Conceptually, moment of inertia is the effective rotational inertia of a rotating body. It depends of the object`s mass and its distribution about the axis of rotation. D. The effective mass of an object that is rotating. Quiz by Dr. John Dayton

13. 12. A small steel ball of 1 kg mass is being spun in a circle at the end of a 1.5 m string. What is the moment of inertia of this system? A. 2.25 kg.m2 B. 1.5 kg.m2 C. 3.0 kg.m2 D. 1.0 kg Quiz by Dr. John Dayton

14. 13. What effect will there be if an unbalanced torque of 5 N.m acts on an object whose moment of inertia is 0.5 kg.m2? A. it will accelerate at 10 rad/s2 B. it will accelerate at 0.1 rad/s2 C. nothing, since it is not rotating D. it will accelerate at 2.5 rad/s2 Quiz by Dr. John Dayton

15. 14. A disk of mass 2 kg and radius 2 m is traveling 1 m/s and rotating at 3 rad/s. What is the disk’s total kinetic energy? A. 18J B. 1 J C. 19 J D. 4 J Quiz by Dr. John Dayton

16. The orbit of a certain asteroid varies in distance from the Sun from 4 AU to 2 AU. When the asteroid is 4 AU from the sun its speed is vo. What is its speed when it is 2 AU from the Sun? • 1 AU = 1.5x1011m (astronomical unit) A. vo B. vo/2 C. 2vO D. 4vo When you encounter problems like this it is not enough to guess at the correct answer. You have to know and understand why the correct answer is correct and how to determine it. If you don’t know, ask questions. Quiz by Dr. John Dayton

17. 16. A sphere of radius 0.5 m and mass 12 kg rotates about an axis through its center at 20 rad/s. What is the sphere`s angular momentum? A. 5.0 kg.m2/s B. 24 kg.m2/s C. 1.2 kg.m2/s D. 240 kg.m2/s This is the last question of this quiz. Quiz by Dr. John Dayton