Physics--Chapter 19: Liquids

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force/area

What is the relationship between liquid pressure and depth of a liquid? Between liquid pressure and density?

liquid pressure increases with depth; it increases with density

By how much does the water pressure on a submarine change when the submarine dives to double its previous depth (neglect the very real effect of atmospheric pressure above)? If the submarine operated in fresh water, would the pressure it feel be greater or less than at the same depth in salt water?

doubles
less because density of fresh water is less

same

If you immerse a tin can with a small hole in it in water so that water spurts through the hole, what will be the direction of water flow where the hole is?

perpendicular to the surface of the can

Why does the buoyant force act upward for an object submerged in water?

there is greater pressure against the bottom

same

Why does the buoyant force on submerged objects not act sideways?

pressure on each side is the same

same

1 kg; 9.8 N

Does the buoyant force on a submerged object depend on the weight of the object itself or on the weight of the fluid displaced by the object? Does it depend on the weight of the object itself or on its volume? Defend your answer.

Weight of fluid displaced
volume; the volume of the submerged object determines the volume of the fluid displaced

When the buoyant force on a submerged object is more than the weight of the object, how do the densities of the object and water compare?

object's density is less

When the buoyant force on a submerged object is less than the weight of the object, how do the densities of the object and water compare?

object's density is greater

100 tons

According to Pascal's principle, what happens to the pressure in all parts of a confined fluid when you produce an increase in pressure in one part?

Pressure increases equally in all parts

What are the key factors that determine the pressure exerted by the liquid?

density and depth

At, any point in a liquid, the forces that produce pressure are exerted in what way?

equally in all directions

the surface

At greater depths, the force what?

gets greater and the velocity of the escaping liquid is greater

Pressure of the liquid does NOT depend on what?

amount, volume, or total amount of liquid

The dam that must withstand the greater pressure is: the large, but shallow lake or the small, but deep lake??

small but deep lake...because it is the dam with the deepest water behind it, not the most water

When you are swimming in water, do you feel different amounts of pressure when you tilt your head on your ears?

no, you feel the same amount of water pressure on your ears because at any point within a liquid, the forces that produce pressure are exerted equally in all directions

buoyancy

buoyancy force

When the weight of a submerged object is equal to the buoyant force, the submerged object will...

remain at any level or will be suspended

A completely submerged object will always displace what kind of water?

displaces a volume of liquid equal to its own volume

What happens when there is a net upward force or a buoyant force?

the upward forces against the bottom of a submerged object are greater than the downward forces against the top...the forces acting horizontally against the sides cancel each other out

sink

When the weight is equal to the buoyancy force, the submerged object will?

remain at any level, like a fish

When the weight is less than the buoyant force, the object will?

rise to the surface and float

displaced

rise

The volume of water displaced is equal to what?

the volume of the object

its own volume

What does Archimedes' Principle describe the relationship between?

buoyancy and displaced fluids

An immersed object is buoyed by a force equal to the weight of the fluid it displaces

Archimedes' Principle

immersed

True or False. The shape of the object changed the buoyant force equally the weight of liquid displaced.

False...this holds true at any depth

Archimedes' Principle holds true for what two things?

liquid and gases...both fluids

9.8 N

Is the weight of the displaced water or the the weight of the submerged object the buoyant force when an object is completely submerged?

the weight of the displaced water

According to Archimedes' Principle, what equals the weight of liquid displaced?

the upward force due to water pressure, minus the downward force due to water pressure on the top

Why does the depth of the submerged object make no difference?

because although there is more pressure at greater depths, the difference in pressures on the bottom and top of the block is the same at any depth

What are the 3 simple rules when it comes to sinking and floating?

1) an object more dense than the fluid in which it is immersed sinks
2) an object less dense than the fluid sinks
3) an object with equal density to the fluid neither sinks nor floats

the buoyant force on a submerged object depends on what?

volume, NOT WEIGHT...a smaller object displaces less water so has a smaller buoyant force acting on it...a larger object displaces more water so a larger buoyant force acts on it

What would happen if a fish were somehow bloated up? Swallowed a stone?

-it would be less dense than the water and float to the top
-it would sink to the bottom

What do we say about people, who try but cannot float?

they are too dense...to float more easily, you must reduce your density...since weight density is weight divided by volume, you must eight reduce weight or increase volume...taking in a lung full of air can increase your volume...a life jacket would increase your volume but add little weight

How does a submarine control its density?

by controlling the flow water into and out of its ballast tanks

How does a fish regulate its density?

by expanding or contracting an air sac that changes its volume...a fish can move upward by increasing its volume which decreases density and downward by contracting its volume which increases density

How does a crocodile increase its density?

swallowing stones...with its increased density it can swim lower in the water and expose itself less to prey

a floating object displaces a weight of fluid equal to its own weight

Principle of Floating

True or False. Archimedes' principle holds true whether or not an object sinks or floats

true...in the case of floating, the buoyant force equals not only the weight of liquid displaced, but also the weight of the floating object

Why does a 1-ton iron block sink, while a 1-ton iron bowl float?

The iron bowl will still weigh 1 ton...but when you lower the bowl into a body of water, it displaces a greater volume of water than with the iron block...the deeper the bowl is immersed, the more water is displaced and the greater water equals the weight of the bowl, it will sink no further...it will float because the buoyant force now equals the weight of the bowl

What does Pascal's Principle deal with?

the transfer of pressure through enclosed fluid objects

Changes in pressure at any point in an enclosed fluid at rest are transmitted undiminished to all points in the fluid and act in all directions

Pascal's Principle

Are the ideas of efficiency compromised?

No, the law of conservation of energy is not compromised...the increase in force is compensated for by a decrease in distance moved

hydraulic press

What does Pascal's Principle apply to?

all fluids whether gases or liquids

What is a typical application of Pascal's Principle for gases and liquids?

automobile lift...compressed air exerts pressure on the oil in an underground reservoir. the oil in turn transmits the pressure to a cylinder, which lifts the automobile

the top floor of a building is 30 m above the basement. calculate how much greater the water pressure is in the basement compared with the pressure at the top floor

1000 x 9.8 x 30= 2.9 x 10^5 Pa

Why does water seek its own level?

water wants to have equal pressure, but pressure is already equal in all directions

why is it inaccurate to say that heavy objects sink and light objects float?

depends on density of object compared to fluid it was put into

compared with an empty ship, would a ship loaded with a cargo of foam insulation sink deeper into water or rise in water?

sink deeper because it is adding mass without any volume

A) a half-filled bucket of water is on a spring scale. If a live fish is placed in it, what happens to the reading on the scale? B) Would your answer be different if the bucket were initially filled to the brim?

A) yes, increase by the weight of the fish
B) yes, the weight of the fish will fall out of the top of the fish

Example: