Question

a ball weighing 4kg of density 4000kg/m3 is completely immersed in water of density 1000kg/m3. find the buoyant force

Answer 1

Mass of ball = 4kg
Density of ball = 4000kg/m³
So, volume of ball,
4000/1 = 4/x
x = 4/4000 = 1/1000 = 0.001
Volume of ball = Volume of liquid displaced = 0.001 m³

Density of liquid = 1000kg/m³
Weight of liquid displaced =
1000/1 = y/0.001
y = 1kg
Now, according to Archimedes principle, the upthrust is equal to the weight of water displaced.
Upthrust = 4

Answer 2

Mass of ball m = 4 kg Density of ball ρ = 4000 kg/m3 Volume of the ball V = m/ρ = 4/4000 m3 = 10-3 m3. Buoyant force or upthrust acting on the ball                     = Volume of water displaced x density of water x acceleration due to gravity                    = 10-3 m3 x 1000 kg/m3 x 9.8 m/s2                     = 9.8 kg. m/s2                     = 9.8 N.