A raft is made using a number of logs (TBD) with 25-cm diameter and 2-m-length. It is desired that a maximum 90 percent volume of each log w

Question

A raft is made using a number of logs (TBD) with 25-cm diameter and 2-m-length. It is desired that a maximum 90 percent volume of each log will be submerged when carrying two boys with 400 N each. Determine the minimum number of logs that must be used. The specific gravity of the log is 0.75.

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Trúc Chi 3 years 2021-07-25T02:56:01+00:00 1 Answers 301 views 0

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  1. thuthao
    0
    2021-07-25T02:57:37+00:00
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    Answer:

    6logs

    Explanation:f

    First finding the volume of the logs

    V= π/4d²l

    = 0.098m³

    So number of logs will be

    Weight of 2 boys + weight of log = buoyancy force.

    So

    2( 400)+ N ( Mlog x g) = density of water x volume displaced x g

    2(400) = N x 0.098x 1000x 9.8 x 0.9- 0.75* 1000

    N= 5.5 which is approx 6logs

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