A ball whose density is 0.4 x 103 kg/m3 falls into water from a height of 9 cm . To what depth does the ball sink?

The velocity of ball before entering the water surface:v=2gh=2g×9When ball enters into water, due to the upthrust of water, the velocity of ball decreases (or retarded). Retardation, a= Apparent weight  Mass of ball =V(ρ−σ)gVρ=ρ−σρg=0.4−10.4×g=−32glf h be the depth up to which the ball sinks. Then0−v2=2×−32g×h⇒2g×9=3gh∴h=6cm