a raft of dimensions 2m wide by 3m long by. 5m thick is floating in a pond if one fourth of the raf is submerged find the density of the raft material

250 kg/m3

Explanation:

The total volume of the raft is length times width times height

V = lwh = 2 * 3 * 0.5 = 3 m cubed

The volume of the raft that is submerged in water is 1/4 of total volume

3 / 4 = 0.75 m cubed

Let water density = 1000 kg/m cubed and g = 10 m/s2

The buoyant force is equal to the weight of water displaced by the raft

F = 0.75 * 1000 * 10 = 7500 N

This force is balanced by the raft weight, so the weight of the raft is also 7500N

Mass of raft is 7500 / g = 7500 / 10 = 750 kg

Raft density is mass divided by volume = 750 / 3 = 250 kg/m3