Question

An iron ball of density 7.8 g/cm³ and volume 200 cm³ is totally immersed in water.Calculate the up thrust on it.

Answer 1

upthurst force = vdg
where v = volume of iron ball = 200*10^-6 m³
          d = density of water = 1000kg/m³
          g = gravitational force = 9.8 m/s²
upthurst force = 200*10^-6*1000*9.8
                     = 1.96N

Answer 2

When a body is immersed in a liquid, the upthrust is
F = ρvg

here;
liquid is water, so ρ=1000 kg/m³
volume, v = 200 cm³ = 200×10⁻⁶ m³
g = 9.8 m/s²

Upthrust, F = ρvg = 10³ × (200×10⁻⁶) × 9.8 = 1.96 N