Question

with what acceleration does an aluminum p= 2800 kg/m³ sphere fall under water p=1000kg/m³, ignore drag force

Answer 1

When the aluminium sphere fall under water only buoyant force will act on it as we need to neglect the drag force.

Let F be the buoyant force

where V_s is the volume of sphere

  is the density of fluid (water) = 1000 kg/m³

g is the gravitational constant = 9.81 m/s²

Let m_s be the mass of sphere

be the density of sphere = 2800 kg/m³

Then

Now F is also given as

a is the acceleration of aluminium sphere

Putting (1) = (3)

Putting value of V_s from (2) in (4)