physics fluid buoyant force

Main Menu

Problem# h2phy1 - Pressure converted inside the Aorta

Problem# h2phy2 - Pressure inside vein

Problem# h2phy3 - Pressure on the floor

Problem# h2phy4 - Pressure under the sea

Problem# h2phy5 - Pressure between oil and water

Problem# h2phy6 - Buoyant Force

The density of fluid "A" is 1.2 times of density fluid "B".
When we bring an object lower into the liquid "B", and
find that volume of the object sunk down is 0.6 times of total volume.
If we take this object lower into the liquid "A", and sunk down, what is
the ratio of lower portion into liquid "A" comparing with the total volume?

Strategy - the rule "Must have" of Mr.Zhang ®

Fb= ρvg

Solution

Consider, force acts against object when 1st. lowering into the “B” liquid ;

ΣFup=ΣFdown

Fb=mg

ρbg(0.6V)=mg

ρb(0.6V)=m     → (1)

Consider, force acts against object when 2nd. lowering into the “A” liquid ;

ΣFup=ΣFdown

Fb=mg

We represents Vx  with the portion which sunk down into liquid "A"

ρag(vx)=mg     → (2)

From the problem gives ρa=1.2ρb,and we also take the equation(1) substitue in equation(2) , therefore,

1.2ρbg(vx)=0.6ρbvg

1.2ρb(vx)=0.6ρbv

1.2(vx)=0.6v

vx= 0.6v 1.2

vx=0.5v

Ans.  The ratio of lower portion into liquid "A" comparing with the total volume is 0.5v

Brake Booster