A 4 kg block with a 1 kg block stacked on top initially slides at 2 m/s on a rough, horizontal
surface. The blocks continue to move as a unit with no sliding between the two. The blocks come to rest 1 m
away.

15. How much work did kinetic friction from the surface below do on the 4 kg block during this process?
a) -2 J
b) -6 J
c) -10 J
d) -14 J
e) -18 J

16. How much work did static friction from the 1 kg block above do on the 4 kg block during this process?
a) +2 J
b) +6 J
c) +10 J
d) +14 J
e) +18 J

17. What is the coefficient of kinetic friction between the 4 kg block and the surface below?
a) 0.35
b) 0.30
c) 0.25
d) 0.20
e) 0.15

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