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Designing a Buoy tether

  • Thread starter Shnitzel
  • Start date
  • #1
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Homework Statement


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.


Homework 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
acceleration

The Attempt at a Solution


Not sure how to start this, I have to solve it in excel but dont know where to begin
 

Answers and Replies

  • #2
gneill
Mentor
20,712
2,714

Homework Statement


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.


Homework 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
acceleration

The Attempt at a Solution


Not sure how to start this, I have to solve it in excel but dont know where to begin
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?
 

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