4/12 Misprint in tonight's HW assignment

     In HW problem #43 in tonight's (4/12) HW, the given
     equation numbers are wrong.  The approximate form
     is in Eq. (12-18).  The exact form can be derived
     from Eq. (12-17).


4/03 Misprint in tonight's HW assignment

     In HW problem #55 in tonight's (4/3) HW, the correct 
     radius of the disk is 12 cm or 0.12 m (not 0.12 cm).


3/31 Some comments are necessary for a few of the HW problems
     at the end of Chapter 9.

#47  The initial angular velocity of the bicycle wheel
     is said to point in the up direction.  This is correct,
     however we will not discuss this use of vectors with
     angular quantities until Chapter 10.  For our
     purposes, 'up' means CCW when viewed from above, and
     'down' means CW when viewed from above (or CCW when
     viewed from below).

#65 and #67

    The picture of the yo-yo in problem 65 might not be
    clear.  The yo-yo consists of two uniform discs connected
    by (and separated by) a "massless" peg of radius r about 
    which the string is wound.  The total mass of the yo-yo is 
    M and the radius of the uniform discs is R.  So the 
    rotational inertia of the yo-yo is the same as the I for a 
    single uniform disc of mass M and radius R, (1/2)MR^2.


3/06  Misprints in tonight's HW assignment:

      #44(b)  The 1.22 m height should be 0.75 m.
      #64     The 6.0 cm length should be 60 cm.


2/23  The solutions for TEST TWO (yellow form) are
      now available at the Noble Library Copy Center.


2/15  Change to office hours and upcoming help session:

      Beginning this week my Monday afternoon office
      hour (3:40-4:40) is cancelled and replaced with
      an hour on Thursday afternoons from 2:40-3:40,
      still in PSF-430.

      There will be a nighttime help session at 7PM
      in PSF-173 on Thursday 2/17.  No test hints will
      be given, no new material will be covered, and
      I will not do HW problems.  I WILL answer your
      questions about concepts that you do not
      understand.

    
2/08  The solutions for TEST ONE (yellow form) are
      now available at the Noble Library Copy Center.


2/02  There will be a nighttime help session at 7PM
      in PSF-173 on Thursday 2/03.  No test hints will
      be given, no new material will be covered, and
      I will not do HW problems.  I WILL answer your
      questions about concepts that you do not
      understand.


1/31    EXCEPTIONS TO HW RULES FOR FRIDAY RECITATIONS:

        Twice this semester (2/04 and 4/07) we have a
   Friday test for which the lecture material on the
   preceeding Wednesday is not covered by that test.
   So for those two Fridays we make the following
   exception to your rules for HW due.

   Fri 2/04  The HW due is from the preceeding Fri (1/28)
             and the preceeding Mon (1/31).  The HW for
             Wed 2/02 is added to the HW due on Fri 2/11.

   Fri 4/07  The HW due is from the preceeding Fri (3/31)
             and the preceeding Mon (4/03).  The HW for
             Wed 4/05 is added to the HW due on Fri 4/14.


   These exceptions apply only to Fri recitations and only
   on these two dates.


1/19    The tests, with solutions, for this instructor's 
   offering of PHY 121 during the first Summer Session 1999 
   are now available at the Noble Library Copy Center.