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Did you complete the reading assignment? (Typically this means at least 20-30
minutes looking over the assigned sections of the book.)
When you carry an object across the room, without lifting it or setting
it down, you do no "mechanical work" on it.
You need to carry a suitcase up a flight of stairs. In which case will you do
the most mechanical work?
You carry the suitcase up quickly.
You carry the suitcase up slowly.
Both cases involve the same amount of work.
The amount of potential energy possessed by an elevated object is
the distance it is lifted
the force needed to lift it
the work done in lifting it
its acceleration due to gravity
Ralph asked me a question about today's reading assignment. According
to the reading assignment, a car coasting from rest
down two hills, one steeper than
the other, would arrive at the bottom of each hill with the same speed, as
long as the two hills have the same vertical height. (Of course, this is
true only if we neglect friction and air resistance.) Ralph wondered how
this could be possible, since as we learned in class the acceleration of the car down the steep
hill will be greater than down the other hill. What should you tell him?
The comments in the next next two boxes go into a big, mostly anonymous text
file that I skim through before the morning lecture, using the comments to help
me plan class discussion. ("Mostly anonymous", because I can track down who made
what comment, but it takes some effort on my part to do so.) Therefore, if you
really want to make sure I see your question/comment and answer it individually,
you should send it to me via email and not through this form.
Which part of today's assignment was particularly hard or confusing? What
would you like to spend extra time on in class?
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