A small wooden block (cuboid) of mass 
floats in water, as shown in the figure below.
The top face of the block is horizontal and has area 
. The density of the water is 
. The block is displaced and released so that it oscillates vertically. The variation with displacement 
of the acceleration 
of the block is measured for the first half oscillation, as shown in the graph below.
Explain why the maximum negative displacement of the block is not equal to its maximum positive displacement.
The mass of the block is 
. Use the graph above to determine the decrease 
in energy of the oscillation for the first half oscillation.
.
