Monday, February 4, 2008
Announcements:
- Our first exam is scheduled for this Friday during class.
If you need to take this exam early, please let me know.
- If you find a mistake in your textbook (especially a
physics-related error), let me know, and you will receive extra credit
if you are the first to identify the error. So far, I have only
found one such mistake (see the note below related to problem #9 in
chapter 5).
- Please
check the list of clicker ID numbers to ensure that the clicker you
have been using is properly listed. Also write in the
letter-number code that corresponds with your clicker (ex. "AA6").
- I
will soon be posting participation scores on Blackboard so that you can
confirm that your participation in class is being counted accurately.
Assignments:
- Answer the recommended conceptual exercises and problems for
Chapter 5, and check your understanding by
looking at the answers in the back of the textbook. Note:
The answer to problem 9 should be 3.6 x 10^22 N (not 3.6 x 10^33 N as
stated in the back of the textbook).
Class Discussion:
Chapter 5 - Gravity
Fg = G*m1*m2/d^2 where G = 6.7 x 10^-11 N*m^2/kg^2 is the
Universal Gravitational Constant
Weight is the total gravitational force on an object.
Objects in orbit are not weightless, they just appear to be weightless.
Which body exerts a stronger gravitational pull on the moon: the
Earth or the Sun?
Useful solar system data:
mass of Earth = 5.97 x 10^24 kg
mass of moon = 7.35 x 10^22 kg ~ 1/81 mass of Earth
mass of Sun = 2 x 10^30 kg
radius of Earth = 6370 km = 3950
radius of moon = 1740 km = 1080 mi ~ 1/4 radius of Earth
radius of Sun = 700,000 km = 432,000 mi
Estimate the weight of an object on the moon compared to Earth given
the facts that m(Earth)/m(moon) = ~100, and r(Earth)/r(moon) ~ 4.
What are the consequences of Newtonian thinking?
What limitations are there in our world today due to Newtonian thinking?
Examine Fig. 5.16 - Excellent summary of physics
Why not use the more modern and accurate theories instead of F = ma?
Video clip: Toyota Tundra truck accelerating along straight road
beats a set of bay doors that are closing and then stops just before
reaching the end of the road that is above the Grand Canyon. What
examples of physics are demonstrated in this commercial? How could we estimate the acceleration of the truck?
Video Clip: During last year's Superbowl (41) , there was a
commercial that showed a FedEx
office on the moon. There are at least half a dozen examples
of "bad" physics in this 30-second advertisement that cost $2.6 million
to air. In groups of no more than 3 students, identify the impossible events shown in this advertisement. Extra
credit will be awarded to the group with the most correct examples.
Minute Paper:
1) What is the most important thing you learned today?
2) What questions do you have (particularly in preparation for the first exam)?