Answers to those Homework Problems that you must
write up and turn in at recitation (i.e. the HW 
problems not on the Mastering Physics web site)
will be posted here.
Fishbane Problems - Chapter 4
24. (a) 0.889 m/s² right
    (b) netF=1.78 N right; F_12=6.22 N left
        (also gravity, normal force, and 8 N force)
    (c) netF=2.67 N right; F_23=3.56 N left; F_21=6.22 N right
        (also gravity and normal force)
    (d) netF= 3.56 N right; F_32=3.56 N right
        (also gravity and normal force)
    (e) netF=1.78N right; F_12=1.78N right
        (also gravity and normal force)
Fishbane Problems - Chapter 5
32. (a) 5.88 N when applied to upper block
    (b) 8.82 N when applied to lower block
HRW - Chapter 6
36. (a) zero 
    (b) -112 W
Serway Problems - Chapter 8
56. (a) 14.0 cm/s
    (b) 4.00 mm
    (c) same answers by a different method;
        the method is what counts here
HRW - Chapter 8
34. (a) 3.50 m/s
    (b) 9.50 J