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When the Tucurui Dam was constructed in northern Brazil, the lake that was created covered a large forest of valuable hardwood trees. It was found that even after 15 years underwater the trees were perfectly preserved and underwater logging was started. During the logging process a tree is selected, trimmed, and anchored with ropes to prevent it from shooting to the surface like a missile when cut. Assume that a typical large tree can be approximated as a truncated cone with a base diameter of 8 ft , a top diameter of 2 ft , and a height of 100 ft . Determine the resultant vertical force that the ropes must resist when the completely submerged tree is cut. The specific gravity of the wood is approximately 0.6.

User Georgian
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Answer:
F_(net)=803.712 lbf

Step-by-step explanation:

Given


d_1=8 ft


d_2=2 ft

height=100 ft

specific gravity=0.6


Volume of tree=(\pi \cdot h)/(3)\left [ r_1^2+r_2^2+r_1r_2\right ]


V=(\pi \cdot 100)/(3)\left [ 8^2+2^2+8\cdot 2\right ]


V=8798.6 ft^3

Now net upward force on log


F_(net)=\rho _(water)Vg-mg


F_(net)=\left ( \rho _(water)-\rho \right )Vg


F_(net)=\left ( 1-0.6 \right )* 62.4* 32.2


F_(net)=803.712 lbf

User Forvas
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