A ball weighting 4 kg of density 4000 kgm^-3 is completely immersed in water of density 1000kgm^-3. Find the apparent weight of the ball in water.(g=10ms-1)

Apparent weight = Actual weight – Buoyancy

Now,

Buoyancy = (volume of water displaced) × density of water × g

=> Buoyancy = volume of the ball × density of water × g

=> Buoyancy = (mass of ball/density of ball) × density of water × g

=> Buoyancy = (4/4000) × 1000 × 10 = 10 N

Thus,

Apparent weight = 4 × 10 – 10

=> Apparent weight = 30 N