Q.

The bulk modulus of a spherical object is 'B'. If it is subjected to uniform pressure 'p', the fractional decrease in radius is           [2017]

1 B3p  
2 3pB  
3 p3B  
4 pB  

Ans.

(3)

Bulk modulus B is given as

  B=-pVΔV                                 ...(i)

The volume of a spherical object of radius r is given as

     V=43πr3,  ΔV=43π(3r2)Δr

   -VΔV=43πr343π3r2Δr or -VΔV=-r3Δr

Put this value in eqn. (i), we get B=-pr3Δr

Fractional decrease in radius is -Δrr=p3B