9. one point, from Lecture 9, involves calculation and doing an actual experiment

(a) .4 Work and Potential. What is the difference between an elastic and an inelastic collision? (.1)
What is negative work? (.1)
What is the meaning of the word ``potential'' in potential energy? (.1)
What did the bowling ball in my face demonstrate? (.1)

(b) .3 Conservation of Energy. A high jumper runs at v=6m/s, makes a perfectly efficient jump, and sails to what height? (It would be his/her center of mass that would rise that far.) You must use conservation of energy to solve the problem, even if there's another way. Use g=10m/s². Show your work! You may be surprised that the answer doesn't depend on the jumper's size in this idealized world of physics laws about simple, ``perfect'' systems. (.3)

(c) .3 How Powerful are You? Students in physics courses with labs are required to run up the Sterling Hall stairs as part of one of their labs. I'd like you to do something similar, but it's OK if it's fairly crude. If you are physically unable to do this, call me or write me a note AT ONCE, and I'll give you an alternate problem.
Do this with a partner if possible. Pick some stairs, for example two or three flights in Sterling Hall, or in a dorm. It should be a significant number, longer than one average flight. Take a ruler and a stopwatch or at least a watch with seconds displayed. Measure the total height you will be raising your body, convert it to meters (1m=39.37in, or 1in=2.54cm), then run up the stairs as fast as you can, timing yourself. It won't be very accurate, but calculate your power output. You'll need your mass, using 1kg=2.2lbs, so divide your weight in lb by 2.2 to get the number for your mass in kg. Use g=10m/s². Show your work! (.3)

Revised September 22, 1997.