Physics Help Forum Pressure - Tension Problem

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 May 9th 2018, 07:51 PM #1 Junior Member   Join Date: May 2018 Posts: 3 Pressure - Tension Problem A moored contact mine is an explosive tethered by a cable to the seafloor so that it sits just under the surface of the ocean, then explodes when a ship hits it. Imagine one is a 300 kg sphere with a radius of 0.600 m. If it is 4.00 m below the surface and the tether is low mass enough to be negligible, what is the tension in the tether? Pbot = ptop + density*g*height pbot = 101300 + (1030)(9.81)(4) F/A = 141717.2 F = 141717.2 * pi * .6^2 F = 160197.1N Is this force the correct force which I am trying to find?
 May 9th 2018, 11:45 PM #2 Senior Member   Join Date: Apr 2017 Posts: 499 it shouldn't matter whether it's 4 or 400 meters below the surface , the tension will be the same unless density of water changes with depth you have the radius , so calculate the volume , what is the formula for the volume of a sphere??, then with the density of seawater you can calculate the up force ... topsquark likes this. Last edited by oz93666; May 9th 2018 at 11:48 PM.
May 10th 2018, 12:11 AM   #3
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Join Date: May 2018
Posts: 3
 Originally Posted by oz93666 it shouldn't matter whether it's 4 or 400 meters below the surface , the tension will be the same unless density of water changes with depth you have the radius , so calculate the volume , what is the formula for the volume of a sphere??, then with the density of seawater you can calculate the up force ...
FBuoyancy = density*volume*g
(1030)(4/3)(pi)(.6)^3(9.81)

Then Fnety = 0 = FBuoyancy - Tension - mg
Could I solve for tension this way?

 May 10th 2018, 03:29 AM #4 Senior Member   Join Date: Apr 2017 Posts: 499 yes , that's the only way

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