In Fig. $12-39,$ a 55 $\mathrm{kg}$ rock climber is in a lie-back climb
along a fissure, with hands pulling on
one side of the fissure and feet
pressed against the opposite side. The fissure has width $w=0.20 \mathrm{m}$
and the center of mass of the climber
is a horizontal distance $d=0.40 \mathrm{m}$
from the fissure. The coefficient of static friction between hands and
rock is $\mu_{1}=0.40,$ and between boots
and rock it is $\mu_{2}=1.2$ . (a) What is the least horizontal pull by the hands and push by the feet that
will keep the climber stable? (b) For the horizontal pull of
(a), what must be the vertical distance $h$ between hands and feet? If the climber encounters wet rock, so
that $\mu_{1}$ and $\mu_{2}$ are reduced, what happens to $(\mathrm{c})$ the answer to $(\mathrm{a})$ and $(\mathrm{d})$
the answer to $(\mathrm{b}) ?$