26. The mass of the cylinder is m = ρ(πd
2
1
/4)H, where d
1
is the diameter of the cylinder. Since it is in
equilibrium
F
net
= mg
− F
r
=
πHd
2
1
gρ
4
−
πd
2
1
4
2I
c
= 0 .
We solve for H:
H
=
2I
gcρ
=
2P
πd
2
/4
1
gcρ
=
8(4.60 W)
π(2.60
× 10
−3
m)
2
(9.8 m/s
2
)(3.0
× 10
8
m/s)(1.20
× 10
3
kg/m
3
)
=
4.91
× 10
−7
m .