Q: A cubical block of wood of side *a* and density ρ floats in water of density 2ρ . The lower surface of the cube just touches the free end of a massless spring of force constant K fixed at the bottom of the vessel. The weight W put over the block so that it is completely immersed in water without wetting the weight is

(a) $ \displaystyle a(a^2 \rho g + K ) $

(b) $ \displaystyle a(a \rho g + 2K ) $

(c) $ \displaystyle a(\frac{a\rho g}{2} + 2K ) $

(d) $ \displaystyle a(a^2 \rho g + K/2 ) $

Ans: (d)