1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Designing a Buoy tether

  1. Sep 18, 2012 #1
    1. The problem statement, all variables and given/known data
    Consider a buoy in the form of a vertical right circular cylinder of outside diameter (D) of 8 feet, and
    height (H) of 12 feet. The buoy is a hollow cylinder formed of glass-fiber-reinforced plastic (FRP)
    that is ½-inch thick. The buoy is to be placed in a large river and tethered to the bottom by a cable
    that is 80 feet long
    The cable is supposed to snap if the water depth exceeds 90 feet. Set up an
    Excel spreadsheet to compute the force on the cable at different river depths and the force at which
    the cable should be designed to snap.

    2. Relevant equations
    Archimedes Pinciple: mass of obj- apparent mass of obj= Density of water * vol of obj
    The force on the cable can be computed from a force balance on the buoy.
    The downward force due to gravity is the total mass of the buoy multiplied by gravitational

    3. The attempt at a solution
    Not sure how to start this, I have to solve it in excel but dont know where to begin
  2. jcsd
  3. Sep 18, 2012 #2


    User Avatar

    Staff: Mentor

    Hi Shnitzel, Welcome to Physics Forums.

    To start off, why not perform the calculation by hand for one particular case. That will at least tell you what constants, variables and formulas you'll need to implement.

    So, suppose that at some time the river is 85 feet deep. What's the tension on the buoy cable?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook