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13 terms

Chap 9: Quizzes

STUDY
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Suppose you have one cubic meter of gold, two cubic of silver and six cubic meters of aluminum. Rank them by mass from smallest to largest
A. Gold, aluminum, silver
B. Gold, silver, aluminum
C. Aluminum, gold, silver
D. Silver, aluminum, gold
Mass = density x volume
Mass(G) = 19.3 x 10^3 x 1 = 19.3 x 10^3
Mass(S) = 10.5 x 10^3 x 2 = 21 x 10^3
Mass(A) = 2.7 x 10^3 x 6 = 16.2 x 10^3

C. Aluminum, gold, silver
A giant oil storage facility contains oil to a depth of 40.0m. How does the pressure at the bottom of the tank compare to the pressure at the length of 40.0m in water? Explain
P(bottom) = P(atm) + (density x g x h)
Water density > Oil density

The pressure exerted by a column of water is greater than the pressure exerted by a column of oil
Rank by the amount of fractional increase in length under increasing tensile stress, from smallest to largest: Rubber, tungsten, steel, aluminum
Delta L = (FLi)/YA
Y>, Delta L <
Y - Rubber = 0.1 x 10^7
Y - Tungsten = 35 x 10^10
Y - Steel = 20 x 10^10
Y - Aluminum = 7 x 10^10

Tungsten- Steel-Aluminum-Rubber
A defensive lineman of mass M = 125kg makes a flying tackle at Vi = 4 m/s on a stationary quarterback of mass m = 85kg, and the lineman's helmet makes solid contact with the quarterbacks femur. What kind of stress would be sustained by the lineman? What parts of his body would be affected?
The lineman's skull and neck would undergo compressional stress
Rank the following substances in order of the fractional change in volume in response to increasing pressure, from smallest to largest: Copper, Steel, Water, Mercury
Delta Volume = - (Volume x delta pressure)/bulk modulus

bulk>, Delta volume <

B - Steel = 16 x 10^10
B - Copper = 14 x 10^10
B - Mercury = 2.8 x 10^10
B - Water = 0.21 x 10^10

Steel - Copper - Mercury - Water
The pressure at the bottom of a glass filled with water (density = 1000kg/m^3) is P. The water is poured out and the glass is filled with ethyl alcohol (density = 806kg/m^3). The pressure at the bottom of the glass is now

B. Equal to P
C. Larger than P
D. inderterminate.
P(bottom) = P(atm) + (density x g x h)
Water density > Ethyl alcohol density

The pressure exerted by ethyl alcohol is smaller than the pressure exerted by water

A. smaller than P
Why does air pressure decrease with increasing altitude?
At high altitude, the column of air above a given area is progressively shorter and less dense, so the weight of the air column is reduced. Pressure is caused by the weight of the air column, so the press is also reduced.
Why do water containers and gas can often have a second, smaller cap opposite the spout through which fluid is poured?
As fluid pours out through a single opening, the air inside the can above the fluid expands into a larger volume, reducing the pressure to below atmospheric pressure. Air must then enter the same opening going the opposite direction, resulting in disrupted fluid flow. A separate opening for air intake maintains air pressure inside the can without disrupting the flow of the fluid
Blood pressure is normally measured with the cuff of the sphygmomanometer around the arm. Suppose the blood pressure is measured with the cuff around the calf of the leg of a standing person. Would the reading of the blood pressure be
A. the same here as it is for the arm
B. Greater than it is for the arm
C. Less than it is for the arm.
B. Greater than it is for the arm

P = density x g x h
h>, P>
The blood pressure measured at the calf would be larger than that measured at the arm. If we imagine the vascular system of the body to be a vessel containing a liquid (blood), the pressure in the liquid will increase with depth. The blood at the calf is deeper in the liquid than that at the arm and so it is is at higher pressure.
The magnitude of the buoyant force on a completely submerges object depends on the object's density?
A. True
B. False
B. False

The buoyant force acting on the submerged object
is equal to the weight of the water which displaces. The weight of the displaced water, in turn, is directly proportional to the volume of the submerged object.
Atmospheric pressure varies from day to day. The level of a floating ship on a high-pressure day is
A. Higher
B. Lower
C. No different than on a low-pressure day.
C. No different than on a low-pressure day.

W = mg = density x volume x g = density x Ah x g = B
h=m/(density x g)

Air pressure does not affect the height.
The density of lead is greater than iron, and both metals are denser than water. Is the buoyant force on a solid lead object
A. Greater than
B. Equal to
C. Less than the buoyant force acting on a solid iron object of the same dimension
B. Equal to

Because the dimensions are the same

The buoyant force acting on the submerged object
is equal to the weight of the water which displaces. The weight of the displaced water, in turn, is directly proportional to the volume of the submerged object.
You observe two helium balloons floating next to each other at the ends of strings secured to a table. The facing surfaces of the balloons are separated by 1-2 cm. You blow through the opening between the balloons. What happens to the balloons?
A. They move toward
B. They move away from each other
C. They are unaffected
A. They move towards each other

Bernoulli's principle - faster moving fluids develop a low pressure.