Contemporary Physics I – HW 8
HW 8
Due December 8, 2006
Please answer all questions clearly and concisely. While you need not transcribe the question
completely, it should be clear from your answer alone what you are talking about.
You are strongly encouraged to discuss the homework with your classmates, but you must complete
the written homework by yourself, and of course, the material you submit must be your own.
Remember, show all of your work!
1) 7.3
2) Two identical particles of mass, m= 1kg, are connected by a solid rod of length, l= 2m, and
allowed to pivot around an axis so that at lowest, one of the particles will just barely touch the
ground (as shown).
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a.. When the rod is at an angle θ, as shown, what is the gravitational potential energy of the 1st
mass (with respect to the ground)? The 2nd mass? What is the total potential energy of the
system?
b.. What is the moment of inertia of the system?
c.. Imagine I then add 40 J of energy to the system. What is the rotational kinetic energy
afterwards?
d.. Translational?
e.. What speed will each of the masses have?
f.. What is the instantaneous angular velocity (ω) of the rotation?
3) 8.5
