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Grade 12General Physics

Can you please help me with the solution of question 8 only??

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Profile image of Dx Jayden
6 Years agoGrade 12
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1 Answer

Profile image of Ayush_Deep
ApprovedApproved Tutor Answer6 Years ago
For a rod the change in length dl = Feff L/AY
Feff is the average force which is equal to average force across ends.
Let's assume a force F is applied at one end and other end is rigid (F=0) average force is F+0/2=F/2
In the above question ,
Net force on rod is zero
F + mg = boyant force = 2DVg 
D density of rod 
V volume of rod
m mass of rod
F + DVg = 2DVg 
F= DVg
Boyant force = 2DVg =2F
Therefore force on one end is F and on lower end is 2F
Feff is (F+2F)/2 =3F/2= 3DVg/2
Extension in rod is 3FL/2AY = 3DVgL/2AY=3DL²g/2Y
Hence option 2 is correct
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