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Physics Chapter 13 & 14
Terms in this set (56)
How does pressure relate to force?
Pressure is force per unit area.
Water pressure in a lake is greater __________.
at the bottom.
How does pressure at the bottom of a body of water relate to the weight of water above each square meter of the bottom surface?
The pressure is the weight of the water divided by 1 m2.
What is the relationship between liquid pressure and the depth of a liquid? Between liquid pressure and weight density?
Pressure is proportional to both depth and weight density.
If you swim beneath the surface in saltwater, will the pressure be greater than in fresh water at the same depth?
The pressure will be greater.
How does the water pressure 1 m below the surface of a small pond compare with the water pressure 1 m below the surface of a huge lake?
The pressure will be the same.
If you punch holes in the side of a container filled with water, in what direction does the water initially flow outward from the container?
It flows straight out, perpendicular to the wall.
Why does the buoyant force act upward on an object submerged in water?
The pressure upward on the deeper bottom is greater than the downward pressure on the top.
Why isn't there a horizontal buoyant force on a submerged object?
Force vectors on the sides cancel one another.
How does the volume of a completely submerged object compare with the volume of water displaced?
The volumes are equal.
If an object suspended by a scale shows a weight of 3 N in air, and 2 N when submerged in water, the buoyant force on the submerged object is __________.
How does the buoyant force on a submerged object compare with the weight of the water displaced?
The buoyant force is equal to the weight of the water displaced.
What is the mass of 1 L of water? What is its weight in newtons?
1Kg; 10 N
If a 1-L container is immersed halfway into water, what is the volume of the water displaced? What is the buoyant force on the container?
0.5 L displaced, 5 N buoyant force
An object having the same density as water will __________.
neither sink nor float in water.
Is the buoyant force on a submerged object equal to the weight of the object itself or is it equal to the weight of the fluid displaced by the object?
it is equal to the weight of the water displaced.
What is the condition in which the buoyant force on an object does equal the weight of the object?
The object is neutrally buoyant, so it will neither sink nor float.
Does the buoyant force on a submerged object depend on the volume of the object or on the weight of the object?
What will these objects do in water: an object denser than water, an object less dense than water, an object that has the same density as water.
Sink, float, neither sink nor float
The buoyant force on a floating object is __________.
equal to the object's weight
What happens to the pressure in all parts of a confined fluid if the pressure in one part is increased?
The pressure everywhere increases by the same amount.
When you stand with only one of your feet on a weighing scale, the scale reading is
the same as with both feet.
Sara lies on a bed of sharp nails without harm because
her weight is distributed over 100s of nails.
A completely submerged object always displaces its own
volume of liquid.
The least buoyant force on a rock is when it is submerged
none of the above - (near the surface, near the bottom, halfway to the bottom)
A 5-N block of wood is difficult to fully submerge in a pool of mercury because the buoyant force on the block when submerged is
much more than 5N.
To multiply an applied force while using a simple hydraulic lift, your force should be applied to the
Atmospheric pressure decreases with increasing _________.
How high would you have to go in the atmosphere for half of the mass of air to be below you?
Atmospheric pressure is mainly due to the ___________.
weight of air.
How does the pressure at the bottom of a 76-cm column of mercury in a barometer compare with the air pressure at the bottom of the atmosphere?
the pressures are equal.
Why would a water barometer have to be 13.6 times taller than a mercury barometer?
mercury is 13.6 times denser than water.
When you drink liquid through a straw, is it more accurate to say the liquid is pushed up the straw rather than sucked up the straw? What exactly does the pushing?
The atmospheric pressure outside the straw pushes the liquid toward the lower pressure in your mouth.
Why won't a vacuum pump operate for a well that is deeper than 10.3 m?
Atmospheric pressure equals the pressure under 10.3 m of water and so can push water no higher.
Does the air exert a buoyant force on all objects in air or only on objects such as balloons that are very light for their size?
Air exerts a buoyant force on all objects.
A balloon that weighs 1 N is suspended in air, drifting neither up nor down. (a) How much buoyant force acts on it? (b) What happens if the buoyant force decreases? (c) If the buoyant force increases?
(a) 1 N up; (b) it falls; (c) it rises.
Why are high-altitude research balloons only partially inflated when launched?
The atmospheric pressure decreases as they rise, so they expand. If they were fully inflated at launch, they would burst at high altitudes.
A helium-filled balloon will reach its maximum altitude when __________.
its weight equals the weight of displaced air.
What happens to the internal pressure in a fluid flowing in a horizontal pipe when its speed increases?
The pressure decreases when the speed increases.
What happens to the internal pressure in a fluid flowing in a horizontal pipe when its speed decreases?
The pressure increases when the speed decreases.
How does faster-moving air above an airplane wing affect the pressure on the wing?
The speed increases as the air flows over the wing, so the pressure decreases.
How does faster-moving water between two ships affect the water pressure against the sides of the ships?
Faster-moving water decreases the pressure.
When there is faster-moving water between two ships, are the ships sucked together or pushed together? Explain.
They are pushed together, because faster flow between the ships decreases the pressure between them compared to the exterior pressure.
Is the fluid that goes up the inside tube in a hand sprayer pushed up the tube or sucked up the tube? Explain.
It is pushed up the tube by atmospheric pressure into the low-pressure, fast air stream.
When you stand on one foot instead of two, the force you exert on the floor is
When you stand on one foot instead of two, the pressure you exert on the floor is
more - twice as much.
Water pressure provided by a water tower is greater if the tower
How many forces act on a submerged body at rest in a fluid?
Two - buoyancy and the force due to gravity
The reason a person finds it easier to float in saltwater compared with freshwater is that in saltwater
Neither of these - a person floats higher because a smaller volume of the denser saltwater is displaced.
As you sit in class, is there a buoyant force acting on you?
Yes, due to displacement of air.
Two solid blocks of identical size are totally submerged in water. One block is lead and the other is aluminum. Upon which is the buoyant force greater?
Same on both blocks. - the buoyant force depends upon the volume of the block, since both submerged blocks are the same size, they displace the same volume of water.
On which of these blocks (uranium, aluminum, lead) totally submerged in water is the buoyant force greatest?
1 kg of aluminum. - displaces more water because largest block.
When a submarine takes water into its ballast tanks, its density
When a submerged submarine expels water from its ballast tanks, its density
The maximum height to which water can be drunk through a straw
is 10.3m - at sea level water can not be pushed up by the atmosphere higher than 10.3m
Why don't barometers use water instead of mercury?
Water can be used but the barometer will be too tall. - Water is 13.6 times less dense than mercury
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