Question

A wire is elongated by 2 mm when a brick is suspended from it.  When the brick is immersed in water, the wire contracts by  0.6 mm. What is the density of the brick?

Answer 1

Y=(F/A)/(dL/L) 

{Y=YOUNG'S MODULUS, F= FORCE, A= AREA, dL=CHANGE IN LENGTH, L= LENGTH  

F=Y x dL x A/L  

In First Case F= Mg or D x V x g {D=Density Of Solid, V=Volume}  

In Second Case F= Mg- Upthrust = D x V x g - d x V x g {d Is Density Of Water}  

Put It In Formula And Divide  All Terms Will Be Cancelled left terms will be  

D/D-d=2/1.4  

d=1000 kg/m³  

hence,  

0.7 D = D -1000  

0.3 D = 1000  

D = 3333 Kg/m³