CID# _________________ Quiz #7
Physics 121 Monday, June 2, 2008
1. Which of the disks depicted below would win a rolling race down a ramp? (The dark-shaded features are
holes in the disks.)
2. A sphere rolls without slipping down a ramp. A block slides without friction down the same ramp. Which of
the following statements comparing the descent times of the two objects is true? (a) The rolling sphere takes
longer to descend. (b) The sliding block takes longer to descend. (c) The two bodies have equal descent
times. (d) Insufficient information is given to permit an answer since the descent time of the sphere depends
on its unspecified radius.3. True or False? The dimensions of torque are the same as those of work. (a) True. (b) False.
4. Two yoyos look superficially identical, but a close inspection reveals that the core about which the string is
wrapped has twice the diameter in yoyo A as in yoyo B. Both yoyos are wound, then released at the same
time and allowed to descend. Which of the following statements is true? (a) Both yoyos descend at the
same rate. (b) A descends more rapidly than B. (c) B descends more rapidly than A. (d) Not enough
information is given to allow an answer.5. An electric motor rotates at a uniform rate of 500 rpm. If it is experiencing a frictional torque of 3/π N×m, what
power is it dissapating? (a) 50 W, (b) 200 W, (c) 477 W, (d) 3000 W.
