Properties of Matter 1 Question 6

6. A load of mass Mkg is suspended from a steel wire of length 2m and radius 1.0mm in Searle’s apparatus experiment. The increase in length produced in the wire is 4.0mm. Now, the load is fully immersed in a liquid of relative density 2 . The relative density of the material of load is 8 . The new value of increase in length of the steel wire is

(2019 Main, 12 Jan II)

(a) zero

(b) 5.0mm

(c) 4.0mm

(d) 3.0mm

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Answer:

Correct Answer: 6. (d)

Solution:

  1. When load M is attached to wire, extension in length of wire is

Δl1=MglA.Y

where, Y is the Young’s modulus of the wire.

when load is immersed in liquid of relative density 2, increase in length of wire as shown in the figure is

Δl2=(MgFB)lA.Y

where, FB= Buoyant force

Δl2=(MgMgρlρb)lA.Y[FB=Vρlg=Mgρbρlg]

Here given that, ρlρb=28=14

So, Δl2=(34Mg)lA.Y

Dividing Eqs. (ii) by (i), we get

Δl2Δl1=34Δl2=34×Δl1=34×4mm=3mm

204 Properties of Matter



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