Fluid MechanicsHard
Question
A small solid ball is dropped from a height above the free surface of a liquid. It strikes the surface of the liquid at t = 0. The density of the material of the ball is 500 kg/m3 and that of liquid is 1000 kg/m3. If the ball comes momentarily at rest at t = 2 sec then initial height of the ball from surface of liquid was (neglect viscosity) :
Options
A.20m
B.10 m
C.15 m
D.25 m
Solution
Velocity of ball when it reaches to surface of liquid

a =
; where V is the volume of the ball.
a = 10 m/sec2
apply v = u + at ⇒ 0 =
− 10t
⇒
= 10 × (2)
⇒ 2 × 10 × h = 400 ⇒ h = 20 m Ans

a =
a = 10 m/sec2
apply v = u + at ⇒ 0 =
⇒
⇒ 2 × 10 × h = 400 ⇒ h = 20 m Ans
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