For an extended object, such as a baseball bat, the trajectory of any given
point on the object may be quite complicated. However, the trajectory of
one point, the center of mass, is just the same parabolic trajectory that a
ball would follow.
The center of gravity is a term that refers to the average force of gravity
on an extended object. Except for very large objects, such as the moon, the
center of gravity and the center of mass are the same point. An object
(such as a building) will be in stable equilibrium if a line dropped from
the center of mass falls within the base of support as shown below.
If you complete all of the practice quizzes during the semester, you may
replace your lowest two in-class quizzes with the highest average
of all your on-line quizzes. Since you may take the practice quizzes as often
as you like, your highest average should be pretty good. However, in order
to keep track, you must fill out the student name and id# part of the form.
For this quiz, just click on the part(s) of the figure to correctly
answer the problem.
Page last modified October 6, 2001
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