Review of Fluid

Properties

Density, Pressure, & Buoyancy

What is the density of water?

Ans. 1000 kg/m3 or1 gram/cm3 or 1 gram/ml

George the whale displaces 32 m3 of water when floating at rest

underwater. What is the George’s weight?Ans. 320,000 N

The “tip of the iceberg” that is above the water represents what % of the total iceberg?

Ans. 10%

A cube has a density of 500 kg/m3. Will it float or sink

when placed in water?

Ans. float

A “koosh” displaces 5 grams of water when submerged. What is the volume of the

koosh?

Ans. 5 cm3

What is the volume of the cube shown below?

0.4 m

Ans. 0.064 m3

If the cube shown below is divided into 8 pieces of equal volume, what is the mass of one of the smaller cubes?

32 kgAns. 4 kg

A cube of density 2000 kg/m3 is divided into eight identical smaller cubes. What is the density of one of the smaller

cubes?

Ans. 2000 kg/m3

A cube with a density of 4000 kg/m3 is shown below. What

is the mass of this cube?

0.4 m

Ans. 256 kg

A cube with a density of 4000 kg/m3 is placed into water.

Once the cube is submerged, what will be the buoyant force

acting on it?

0.4 m

Ans. 640 N

A cube with a density of 200 kg/m3 is placed in water. Will

it float? What will be the buoyant force acting on it?

Ans. Yes; cannot determine

What is the density of the cube that is floating in water

as shown below?

1/3

2/3Ans. 667 kg/m3

What is the weight of the 55 kg man?

Ans. 550 N

If the total bottom area of the 55 kg man’s feet is 0.03

m2, what is the pressure at the floor when he

stands on both feet?

Ans. 18,333 Pa

What is the pressure at the floor when the man from the previous slide stands on one

foot?Ans. 36,667 Pa

What is the pressure at a depth of 5 m below the surface

of a lake?

Ans. 50,000 Pa

A treasure chest with a top area of 0.5 m2 sits 20 m below the surface of the sea. What is the force acting on the top?

Ans. 100,000 N

What is the volume of water displaced by the submerged

portion of the cube?

Water level

0.1 m

0.04 m

Ans. 0.0004 m3

What is the weight of the water displaced by the

submerged portion of the cube?

Water level

0.1 m

0.04 m

Ans. 4 N

What is the weight of the cube?

Water level

0.1 m

0.04 m

Ans. 4 N

What is the density of the cube?

Water level

0.1 m

0.04 m

Ans. 400 kg/m3

A hovercraft floats on a cushion of air. If the hovercraft weighs 300,000 N,

and has a base area of 340 m2, what is the pressure at the base?

Ans. 882 Pa

An object that weighs 5 N in air appears to weigh only 3 N

when lowered into water. What is the buoyant force

acting on the object?

Ans. 2 N

An object that weighs 5 N in air appears to weigh only 3 N

when lowered into water. What is the volume of water it

displaces?

Ans. 200 cm3 (0.0002 kg/m3)

A 5000 N car is lifted on a hydraulic piston of area 2000 cm2. What force is needed on the connecting 20 cm2 piston

to do this?

Ans. 50 N

The 3000 N elephant on a 5

m2 piston platform is lifted

by a 0.5 N mouse sitting on a ______

piston plunger.Ans. 8.3 x 10-4 m2

An airship is filled with

helium gas and two inflatable

“ballast” bags of air. Which case below

shows the flow of air when the airship rises?

A

B

Ans. A

For the fire extinguisher to

work, the plunger breaks into the

cylinder at point A. Is the gas in the

small internal cylinder at high or

low pressure?

A

water

Ans. high