Moment of Inertia - General Physics - Solved Past Paper, Exams of Physics

Download Moment of Inertia - General Physics - Solved Past Paper and more Exams Physics in PDF only on Docsity! 1. (20 pts) a) (5 pts) Which would accelerate down a hill (by rolling without slipping) faster, a solid disc or a hoop (both of the same mass and radius)? Just like mass, a larger moment of inertia will result in a smaller acceleration. Since there is more mass further from the axis of rotation in the hoop, it will have a larger moment of inertia (even though both have the same radius and mass). Thus the solid disc will accelerate more quickly. b) (5 pts) Which would accelerate down a hill faster, a block sliding with no friction or a solid cylinder rotating without slipping? Since rotation also requires energy, anything rotating will not have as much energy to put into trans- lation. Thus the solid block (which doesn’t have to put any energy into rotation) will accelerate more quickly. Yet another reason not to lock the wheels of a car when trying to come to a stop. c) (5 pts) Is it possible for an object to be rotating yet still satisfy the conditions for equilibrium? Explain your answer. The criteria include no net force and no net torque. Recall that a non-zero net torque causes angular acceleration. It is still possible for a non-zero (but constant) angular velocity when the angular acceler- ation (and thus the net torque) is zero. So just like an object can be moving with a constant velocity and still be in equilibrium, it is also possible for an object to be rotating with a constant angular velocity and in equilibrium. d) (5 pts) If a pulley was not frictionless, how would you account for this when predicting the motion of the system? Note that this question asks how you would take this effect into account, not how it would affect the motion. So saying that things would move more slowly does not answer the question (even though it is true). The friction would add an additional torque to the pulley. Note that even without friction, the rotation of the pulley would be required to predict the motion of the system. However, the presence of friction adds another torque to the problem. It would also be possible to deal with the friction in terms of energy, though we have not dealt with work done as an object rotates.