Answer

True or false, 2 points each 7. Rotational inertia of an object depends on the axis of rotation of the object. a) True b) False 8. If a ball on a string initially rotates counterclockwise and the angular acceleration is acting clockwise, at some point the ball will change the direction of its angular velocity. a) True b) False 9. In the equation of rotational motion, angular position versus time, the value of angular acceleration is zero. The object will increase its angular velocity. a) True b) False 10. Two people are exerting torques on an already revolving door. The torques are equal in magnitude. One person is turning the door clockwise while the second person is turning the door counterclockwise. The door is acquiring angular acceleration. a) True b) False 1 1. Two children are riding on a merry-go-round. The first child is sitting at a greater distance from the axis of rotation than the second child. The second child has a greater linear (tangential) speed. a) True b) False Calculation problems, 10 points each 12. A vector makes an angle of 1.25 7 with the horizontal axis in polar coordinates. In which quadrant is the vector in Cartesian (x-y) coordinates? 13. A pulley in a crane is making 1 full revolution in 10 seconds. What is the angular speed of the pulley in rad/s? 14. A child is exerting torque of 60 Nm on a merry-go-round, so the merry-go-round acquires an angular acceleration of 0.3 rad/s2. What is the moment of inertia of the merry-go-round? Neglect the moment of inertia of the child. 15. Two equal masses 0.1 kg are located at either end of a very light and rigid rod that has a length of 4 m. What is the rotational inertia (in kg m ) of this system about an axis perpendicular to the center of the rod? 16. A mass mi = 1 kg is located at a distance d1 = 10 cm from the fulcrum on the beam of a simple balance. In order to balance the beam, at what distance from the fulcrum, on the opposite side, should the mass m2 = 2 kg be placed? Assume the gravitational acceleration g = 10 m/s. 17. An ice skater with tucked arms has a moment of inertia of 1 kg m' while spinning at a constant angular velocity of 2 rev/s. The ice skater is extending his arms and slows his spinning down to 1 rev/s. What is his new moment of inertia? 18. The length of a ramp is 3 times longer than the height of the ramp. What is the mechanical advantage of the ramp