How does adding a block to a spring affect its stiffness?

[caitbaby23]

Homework Statement

A spring sticks up from the bottom of the sink, 0.20[m] long ; when a light (ρ=750[kg/m³]) wood block (0.2[m,x]×0.2[m,y]×0.1[m,z]) is attached on top of it, the spring becomes 0.05[m] long.

Homework Equations

mass density = mass / volume
Fspring = -ks

The Attempt at a Solution

a) weight of block = 3kg
stiffness of spring?
b & the others.. ??

 

[gamer_x_]

What do you need to determine?

 

[caitbaby23]

a) calculate the weight of the block, and the spring's stiffness.
b) Write the Forces applied to the block if the sink is filled until the block's top is .05[m] below water surface (ρ=1000[kg/m³]).
c) calculate the Pressure Force on block's top and on block's bottom. (Patmosphere=10000[N/m²])
d) What will the spring's length become, when the block is submerged?

 

[gamer_x_]

- for spring stiffness all you need to think about is the formula for the force exerted by a spring. draw your free body diagram. There will only be two forces...

- what do you think adding water does? the question already gives you a great hint in that it gives you the density of water...