When a 55 N stone is attached to a spring

Question

scale and is submerged in water, the spring scale reads 30 N.
What is the density of the stone?
Answer in units of kg/m3.

Answer 1

apparent weight= 55N-densitywater*g*volumestone

30=55-densitywater*g*volumestone

solve for volume stone
volumestone= 25/(densitywater*g)

density of STone= massstone/volume

= (55/g)/(25/densitywater*g)=55/25 *densitywater

Answer 2

A book is placed on a horizontal wooden plane that is undergoing simple
harmonic motion with an amplitude of 1.0 m. The coefficient of friction
between the book and the horizontal wooden plane is given by = 0.5.
Determine the frequency of the horizontal wooden platform when the book
is about to slip from the horizontal wooden plane.