A thin rectangular piece of wood floats in water. You slowly pour oil with a density equal to that of the wood on the surface of the water until the height of the oil above the water is twice the height of the piece of wood. Which statement is correct?

A. The wood floats on top of the oil, so it sticks up in the air.

B. The wood does not change its position

C. The wood sinks below the surface of the water

D. The wood is half in the water and half in the oil.

E. The wood floats in the oil just above the water.

E. The wood floats in the oil just above the water.

Explanation:

The buoyancy force exerted on an object on fluid can be written as;

Fb = pVg

Where;

p is density

V is the volume

g is acceleration due to gravity

Weight = density * Volume * acceleration due to gravity

For an object that originally float on water, which implies that its density is less than that of water (density of wood less than that of water). If oil with density which equals that of wood is added to the system, the wood would float in the oil just above the water because the buoyancy force from the oil balances the weight of the object, which prevents it from floating on top the oil so it stick up with air.

B. The wood does not change its position

Explanation:

Since the oil has the same density as the wood there will be no buoyant force on the wood by the oil, the wood will remain in its initial position just above the water surface but below the oil surface