A cube of density 3ρ/5 floats in a liquid of density ρ. It is pushed down until it is just completely submerged and released. Neglect drag. If its initial upward acceleration is ng/3, find n.
Physics · Fluid Mechanics · pascal law and buoyant force
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Question

A cube of density 3ρ/5 floats in a liquid of density ρ. It is pushed down until it is just completely submerged and released. Neglect drag. If its initial upward acceleration is ng/3, find n.

G1 Physics · Accepted Answer

When fully submerged, buoyancy=ρVg and weight=(3ρ/5)Vg. Net upward force=(2ρ/5)Vg. Mass=(3ρ/5)V, so a=[(2/5)/(3/5)]g=2g/3. Hence n=2.