You have two blocks of identical size-one made of wood, and one made of lead. a)

Question

You have two blocks of identical size-one made of wood, and one made of lead.

a) Both blocks are completely submerged in fresh water. on which object is the buoyant force the greatest? Why?

b) How does your answer to the previous question change if the wood block instead floats on the surface of the water? Explain your answer

c) A solid ball of unknown material has a mass of 40 g and a volume of 15 cm^2. Will this ball float when placed in fresh water? Defend your answer mathematically!

d) Water flows through a pipe that narrows to a smaller diameter. What happens to the speed of the water in the narrower section of the pipe compared to the wider section - does it increase, decrease or stay the same? What happens to the internal pressure of the water in the narrower section - does it increase, decrease or stay the same?

e)As you know the atmosphere is currently exerting a buoyant force on you. On Venus, the density of the atmosphere at its surface is over fifty times the density of the Earth's atmosphere at the sea level. If could stand on the surface of Venus (and survive) would the buoyant force on you from the atmosphere be greater than, less than, or the same as it is in Houston? Explain...

Explanation / Answer

a)

buoyant force Fb = rho_fluid*Vimmeresed *g

buoyant force is same on both since volumes are same

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b)

immeresed volume for wood is less

buoyant force is more for lead

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c)

density of material = 40/15 = 2.67 g/cc

density of material > density of water (1 g/cc)

the material sink

===============

d)

from equation of continuity

A1*v1 = A2*v2

as the area decreases speed increases

from Bernoullis principle

P1 + (1/2)*rho*v1^2 + rho*g*h1 = P2 + (1/2)*rho*v2^2 + rho*g*h2

as the speed increases pressure decreases

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e)

greater

buoyant force = rho_atmosphere*V*g

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