Prob. $2\mathrm{.}10\mathrm{.}9$ p$.$ IP$-25[$Ans: $7\mathrm{.}77{10}^{9}lb$;$406ft].$

$2\mathrm{.}10\mathrm{.}9$ Video Hoover Dam $($see Video $2\mathrm{.}5)$ is the highest archgravity type of dam in the United States. A cross section of the dam is shown in Fig. P$2\mathrm{.}10\mathrm{.}9$a $.$ The walls of the canyon in which the dam is located are sloped, and just upstream of the dam the vertical plane shown in Fig. P$2\mathrm{.}10\mathrm{.}9$b approximately represents the cross section of the water acting on the dam. Use this vertical cross section to estimate the resultant horizontal force of the water on the dam and show where this force acts.

$($a$)$

$($b$)$

FIGURE P$2\mathrm{.}10\mathrm{.}9$