According to Archimedes' principle, when an object is wholly or partially immersed in a liquid, it experiences a buoyant force which is equal to the weight of liquid diplaced by the object.
The buoyant force acting on the ball, F = Volume of the ball × density of water × acceleration due to gravity
Volume of the ball = Mass of the ball/Density of theball
=kg/4000kg/m3
=0.001m3
The buoyant force acting on the ball,F=0.001m3×1000kg/m3×10m/s2
F = 10 N
The buoyant force acting on the ball = 10 N
The weight of the ball =4kg×10m/s2=40N
The apparent weight of the ball in water = 40 N - 10 N