Answer:[tex]F_{net}=803.712 lbf[/tex]
Explanation:
Given
[tex]d_1=8 ft[/tex]
[tex]d_2=2 ft[/tex]
height=100 ft
specific gravity=0.6
[tex]Volume of tree=\frac{\pi \cdot h}{3}\left [ r_1^2+r_2^2+r_1r_2\right ][/tex]
[tex]V=\frac{\pi \cdot 100}{3}\left [ 8^2+2^2+8\cdot 2\right ][/tex]
[tex]V=8798.6 ft^3[/tex]
Now net upward force on log
[tex]F_{net}=\rho _{water}Vg-mg[/tex]
[tex]F_{net}=\left ( \rho _{water}-\rho \right )Vg[/tex]
[tex]F_{net}=\left ( 1-0.6 \right )\times 62.4\times 32.2[/tex]
[tex]F_{net}=803.712 lbf[/tex]