Science 6 Because The Other Five Weren't Good Enough
did hemisshpere experiminet
Otto von Guericke
117.Which teapot holds more liquid?
The water can be no deeper than the spouts, which are at the same height, so both teapots hold the same amount of liquid.-
table chart showed
densities of materials, etc
submerged
under water
105. Why will the strong man in the previous exercise be more successful in lifting the 10 kg block if he switches places and pushes down on the smaller piston with the block on the larger piston?
-In this case his downward force is multiplied, not divided. He needs only to exert a force equal to one-fiftieth the weight of the 10-kg block. That's 2 N.
73. You know that a sharp knife cuts better than a dull knife. Do you know why this is so? Defend your answer.
A sharp knife cuts better than a dull knife because it has a thinner cutting area which results in more cutting pressure for a given force.
-An immersed body is buoyed up by a force equal to the weight of the fluid it displaces (for both liquids and gases).
Archimedes' principle
120.Compared to an empty ship, would a ship loaded with a cargo of Styrofoam sink deeper or less deeply into water? Discuss and defend your answer.
Deeper because p[rinciple of floation says that floating objects hgave boyyant force equal to weight of object. This jeans that the force will be bigger. The thing is, the only way to do that is by increasing the boyhant force. The boyant force is created by the wieght of water dispalecd as stated by Archimedes Principle. this means that the boat will sink more to solve that
-The amount of matter per unit volume:
Density
-Density formula
Density=massvolume
An aneroid barometer calibrated for altitude is called
an altimeter (altitude meter)
A small portable instrument that measures atmospheric pressure is
aneroid barometer
What they all have in common is that air is made to flow faster over the wing's top surface than under its lower surface. This is mainly accomplished by a tilt in the wing, called its
angle of attack
112.When a steadily flowing gas flows from a larger
diameter pipe to a smaller-diameter pipe, what happens to (a) its speed, (b) its pressure, and (c) the spacing between its streamlines?-112. The speed increases, the pressure decreases, and the streamlines get closer. This is because of Bernoulli's Principle which states that when speed in a fluid increases, internal pressure in it decreases. Secondly, streamlines are the motion of fluid. This all means that when the fluid goes into a narrower path, the lines will have to get closer together to all fit in it, and this means that they begin to add onto each other which increases speed, and form what we have just gathered, as the speed of a fluid increases, it's internal pressure decreases.
one in which the disturbing effects of the forces between molecules and the finite size of the individual molecules can be neglected.
ideal gas
all wings have one thing in common
is that air is made to flow faster over the wing's top surface than under its lower surface.
Boyle's law example
tire
immersed
touching water
iron is _ times as dense as water
8
It is an absence of matter; it is a condition of nothingnes
vacuum
-Liquid Pressure Formula
weight density*depth
Formula for weight density
weight/volume
MErcury Density
13.6g/cm^3
Weight density is expressed as
-weight per unit volume.
100. Would it be slightly more difficult to draw soda through a straw at sea level or on top of a very high mountain? Explain.
100. It would be harder to suck soda throughh a straw on a very high mountain. This is becaue that when you suck through a straw, its not you pulling on the wtaer, it's atmospheric pressure pushing up on it. When you suck, you are getting rid of air presure in the straw. Atmospheric pressure then moves in in all directions to get that area where the pressur eis at, so it moves inside oif the straw the only way it can, from the bottom. It then pushes up to take all that empty space from the air pressure taken by you and the more you suck on the straw, the more air pressure is taken, and thus, the higher the fluid is pushed. In this case, atmospheric pressure lessens as you get higher in the Earth until eventually it becomes negligible. If you were on a high mountain and were to suck from the straw, atmospheric pressure wouldn't be able to exert as much pressure to push the fluid up as it did when you were on ground level simply because there is less of it.
102. Why is it so difficult to breathe when snorkeling at a depth of 1 m, and practically impossible at a depth of 2 m? Why can't a diver simply breathe through a hose that extends to the surface?
102. It's hard to breath with a snorkler at those depths because of atmospheric pressure. The deeper you go, the bigger atmospheric pressure is. In this case, you have a small tube that extends to the surface of the water, when you breath, you are sucking out the air pressure in the tube, which can make the atmospheric pressure crush it. Another thing that could happen is that the pressure outside the tube could be bigger than the pressure inside the tube and crush it or decrease the volume of the tube. You can't just simply breath using a huge hose going to the surface because you will eventually get deep enough to the point where the wate pressure gets so big that it crushes the hose, and now you're at the bottom of the ocean without any air, have fun!
104. In the hydraulic arrangement shown, the larger piston has an area that is 50 times that of the smaller piston. The strong man hopes to exert enough force on the large piston to raise the 10 kg block that rests on the small piston. Do you think he will be successful? Defend your answer.
104. He probably won't be successful. This is because of Pascal's Principle. It states that if a change in pressure occurs in any part of a fluid, that change is transmitted to every part of that fluid. THis means that when our strong friend pushes down on the big piston, he will end up exerting the pressure needed to get to the other side, but that forcewill be transmitted throughout that entire large fluid and divide it when he puts pressure on the big piston, so the pressure will be the same, but the area will get bigger and the force will get smaller when it reacehs the small piston, so chances are, nothing's lifting.
106. Your friend says that the buoyant force of the atmosphere on an elephant is significantly greater than the buoyant force of the atmosphere on a small helium filled balloon. What do you say?-
106. I agree with this because Archimedes' Principle applies to all fluids including air. It states that an object submerged in fluid will be buoyed up by a force equal to the weight of the fluid displaced. In this case, the balloon has a significantly less amount of volume compared to that of the elephant. This means that it will take up less space and therefore displace less air, so the air will buoy up the balloon less than it would buoy up the elephant.
108. A steel tank filled with helium gas doesn't rise in air, but a balloon containing the same gas easily does. Why?
108. The tank has a higher density than the air while the balloon doesn't. This is because when you fill the balloon with helium, you are expanding it and increasing the volume, which in turn decreases the density of both the helium and the balloon itself because the atoms aren't bunched together like they were before they were pushed apart from each other by this inflation. Meanwhile, the tank already is much heavier than the balloon and doesn't expand at all. This makes the tank have a much bigger velocity and therefore not float up in the air no matter how much helium you give it. If anything, the helium is just making the tank barely less dense.
114.How does an airplane adjust its angle of attack so that it is able to fly upside down?
114. The planje would have to adjust it's angle of attack to where the front of the wing is pointing down. This is because when streamlines are closer, speed increases. In order to do that, like the roof of a house, you will need to provide something to block some of the streamlines from moving. This will make them have to get closer to each other in order to get across the wall and not push each other out of the way. This will in turn cause the speed to remain as if you were flying normally.
116.Why is blood pressure measured in the upper arm, at the elevation of your heart?
116. This is because of liquid pressure. When Depth incerases in a fluid, so does pressure, so if you were to go down on your leg, you wold have a much higher blood pressure than your arm.
122.A discussion of the following question raises some eyebrows: Why is the buoyant force on a submerged submarine appreciably greater than the buoyant force on it while it is floating?
122. This is because of Archimedes Principle which states that the buoyant force of a body is equal to the weight of the fluid displaced by the body. This means that when the submarine is fully submerged in the water, it displaces as much water as it [possibly can with its volume being as big as possible. This will yield a higher buoyant force. When it is on the surface, it is not fully submerged, so therefore it is not displacing as much water as it can. This will yield a lesser buoyant force.
128.In the classroom demonstration at Lund University, a vacuum pump evacuates air from a large, empty oil drum, which slowly and dramatically crumples as shown. A student friend says that the vacuum sucks in the sides of the drum. What is your explanation?
128. When you suck out the air pressure in the barrel, you are emptying out the pressure that is keeping the atmospheric pressure from crushing the barrel. When it is empty, the atmospheric pressure is greater than the pressure inside the oil can and the barrel gets crushed from the pressure of the atmosphere.
70. When you squeeze a party balloon between your hands, what happens to the mass of the balloon? To its volume? To its density?
70. When you squeeze a balloon, the mass of it remains the same because mass is the amount of matter in an object. This means that if you were to lower the mass of the balloon, you would have to take a piece off of it or take away some of it's matter, thereby lowering its mass. In this case, you are not doing that and you are just squeezing the atoms of it closer together, so the mass remains the same. The volume lowers because volume is the amount of space an object takes up. If you were to blow a balloon up, it would obviously take up a lot of space, therefore having a lot of volume. If you were to squeeze the balloon, you would be making it smaller because you are pushing the sides of it closer to each other. This will make it take up less space and in turn, make it's volume smaller. Another reason is because volume is inversely proportional to density. This means that when volume goes up, density decreases, and when density increases, volume decreases. This brings us to the density of the balloon. It increases because when volume decreases, density increases. Another reason is that density is the amount of mass per unit volume, basically saying it's the amount of mass per liter or whatever unit for volume you would wish to use. When you blow up a balloon, you stretch it out and therefore, push the atoms of the balloon farther apart from each other. This decreases density because atoms make up matter and the amount of matter in an object is mass and if these atoms are stretched out, there is less matter per unit of volume and thus less mass per unit volume. Therefore, density is decreased.
72. The density of a rock doesn't change when it is submerged in water. Does your density change when you are submerged in water? Discuss and defend your answer.
72. Your density does change when you are submerged in water. This is because density is the amount of mass per unit volume or the mass of a section of space. The formula for density is mass divided by volume. This means that if your mass were to go up, your density would increase and if your volume were to go up, your density would go down. Now, if you were to jump in the water, your lungs shrink as you go deeper into the water, this compresses them and makes the volume smalelr, which therfore makes the density beigger.
78. What common liquid covers more than two thirds of our planet, makes up 60% of our bodies, and sustains our lives and lifestyles in countless ways?-
78. Water covers more than two thirds of our planet, makes up 60% of our bodies, and sustains life and lifestyles in countless ways.
80. Why is it inaccurate to say that heavy objects sink and that light objects float? Give exaggerated examples to support your answer.
80. If a heavy object had a ridiculously large area, it's pressure and density would be really small. If it was put in the water, the buoyant force of the water would try to equal out the force exerted on it, so it pushes up with that force and overpowers the heavy object and keeps it above the water. If the density was too small compared to the water's density it would also be a reason for being pushed on top of the water. If there was a light object that had an incredibly small area, it's pressure would be close to its original force, and it would have a normal density to how much it weighed. If it had a bigger density than the water and the pressure overpowered the buoyant force, it would sink to the bottom.
82. A halffilled bucket of water is on a spring scale. Does the reading of the scale increase or remain the same when a fish is placed in the bucket? (Is your answer different if the bucket is initially filled to the brim?)-
82. When a fish is placed in a bucket that is halfway full of water on a spring scale, the reading of the scale would increase. This is because the fish has weight and mass and is added to the bucket of water and its mass will increase the push on the spring scale and thus increase it's reading. If the bucket was filled to the brim with water and a fish was dropped in there, the reading would remain the same because of displacement. Displacement is basically volume getting pushed out of the way when a new volume takes its place. In this case, water equal to the volume of the fish gets pushed out of the cup in order to make room for the fish. This means that the weight of the bucket remains the same unless the fish weighs more or less than the water displaced. This is true if the water falling out of the bucket doesn't land on the spring scale.
84. Why will a block of iron float in mercury but sink in water?
84. A block of iron will float in mercury but not in water because of Archimedes' Principle. It states that an object submerged in fluid will be buoyed up by a force equal to the weight of the fluid displaced. This means that an object submerged in a fluid will be pushed up by a force that is equal to the weight of the fluid displaced. This means that for a fluid like water that is very lightweight, the force of buoyancy is low, but for a fluid like mercury that is a lot more heavyweight, the force of buoyancy will be a lot higher. Weight and volume are independent of each other, so if 2 m of water were displaced and 2 m of mercury were displaced, those 2 m of mercury would weigh more than those 2 m of water.
86. The mountains of the Himalayas are slightly less dense than the mantle material upon which they "float." Do you suppose that, like floating icebergs, they are deeper than they are high?
86. I do believe that the Himalayas, like icebergs, are deeper than they are high. I believe this because when you cut off part of the mountain, it is pushed up to where it gets back close to its original height. This is just like Archimedes' Principle which states that an object submerged in fluid will be buoyed up by a force equal to the weight of the fluid displaced. When part of the mountain gets cut off, the buoyed force is higher than the mountain and pushes it up until it's weight equals the buoyant force again. Just like Archimedes Principle, it balances itself out to follow that rule by being bouye up to match the force of the fluid that it displaced long ago. It's like an ice cube in a drink, it sinks partiatlly. Prinicple of floation, fluid displaces an obejct equal to it;s weight
88. The Falkirk Wheel in Scotland (Figure 5.17) rotates with the same low energy no matter what the weight of the boats it lifts. What would be different in its operation if, instead of carrying floating boats, it carried scrap metal that doesn't float?
88. They would have to fill one of the other containers up with enough weight that it could balance out the weight of the scrap metal in the other container. According to Archimedes' Principle which states that an object submerged in fluid will be buoyed up by a force equal to the weight of the fluid displaced, if an object were to be floated to the top by the fluid it displaces, that object floating would have equaled out what was lost when water was displaced. In this case, the weight of the fluid displaced does not equal the weight of the object that did the displacing and it sinks to the bottom, which changes the original weight of the container, so the only way to keep the balance on the wheel intact would be to fill the other container up enough so it can equal the weight of the opposite container. This would be a lot harder, but it would be the only way.
90. Both a 50 ton boat and a 100-ton boat float side by side in the gondola of the Falkirk Wheel, while the opposite gondola carries no boats at all. Why do the gondolas nevertheless weigh the same?-
90. The reason the two gondolas weigh the same is because of Archimedes' Principle. Archimedes' Principle states that an object that is submerged in fluid will be buoyed up by a force equal to the weight of the fluid displaced. This means that for the two boats in the one gondola, before they were put in the gondola, it was filled to the brim with water. When the two boats were placed in, however, the water in the gondola was displaced by how much space these boats took up. That way, a good deal of the weight of the water was taken away and replaced by the weight of the two boats which balances out the gondola like nothing was ever put in there.
94. How does the density of air in a deep mine compare with the air density at Earth's surface?
94. The density of air in a deep mine compared to the density on the surface of Earth is greater. This is because of Boyle's Law, which states that the product of pressure and volume is the same for a confined gas as long as the temperature doesn't change. This means that if the volume or pressure were to increase or decrease, the other of the two would do the exact opposite. For example, If the volume were to decrease, the pressure would increase and vice versa. This means for our question that the volume in a deep cave is less than the volume on the surface of the Earth, this means that the pressure of air will be bigger in the cave than the surface of the Earth. This in turn means that the density will be bigger in the cave because volume is inversely proportional to density, so if it were to decrease, density would increase. This means that the volume is smaller in the cave and hence, the air is denser there than the surface of Earth. Boyle's Law also shows for this problem that since pressure is greater underground, so is density because when pressure increases, so does density.
95. The "pump" in a vacuum cleaner is merely a high speed fan. Would a vacuum cleaner pick up dust from a rug on the Moon? Explain.-
A vacuum cleaner wouldn't work on the Moon. A vacuum cleaner operates on Earth because the atmospheric pressure pushes dust into the machine's region of reduced pressure. On the Moon there is no atmospheric pressure to push the dust anywhere.
115.The photo shows physics teacher Marshall Ellenstein walking barefoot on broken glass bottles in his class. What physics concept is Marshall demonstrating, and why is he careful to ensure that the broken pieces are small and numerous? (The Band
Aids on his feet are for humor!)-The concept of pressure is being demonstrated. He is careful that there are numerous small pieces of glass so that his weight is applied over a large contact area so that the sharp glass provides insufficient pressure to cut his feet.
96. It is said that a gas fills all the space available to it. Why, then, doesn't the atmosphere go off into space?
Air has weight which means gravity is pushing down on it. This weight is called atmospheric pressure.
-The pressure exerted against bodies immersed in the atmosphere, resulting from the weight of air pressing down from above. At sea level, atmospheric pressure is about 101 kPa.
Atmospheric pressure
-Any device that measures atmospheric pressure.
Barometer
-The pressure in a fluid moving steadily, without friction or external energy input, decreases when the fluid velocity increases.
Bernoulli's principle
-The product of pressure and volume is a constant for a given mass of confined gas regardless of changes in either pressure or volume individually, so long as temperature remains unchanged:
Boyle's law
-The net upward force that a fluid exerts on an immersed object.
Buoyant force
What happens in a barometer is similar to what happens when you drink through a straw.
By sucking, you reduce the air pressure in the straw when it is placed in a drink. Atmospheric pressure on the drink then pushes the liquid up into the reduced-pressure region. Strictly speaking, the liquid is not sucked up; it is pushed up the straw by the pressure of the atmosphere.
111.How will two dangling vertical sheets of paper move when you blow between them? Try it and see.
In accord with Bernoulli's principle, the sheets of paper will move inward together because air pressure between them is reduced, and will be less than the air pressure on the outside surfaces.
desnest material on Earth
Irdium
131.Invoking ideas from Chapter 2 and this chapter, discuss why is it easier to throw a curve with a tennis ball than with a baseball.
It si easier to throw a curve ball with a ennis ball because it hass less inertia. This means it will r3esist the turning less. The turinging is caused by the spin of the ball. It grabs a streamline and turns it with it and cerates a low pressure area on the side it will curve on.
77. If water faucets upstairs and downstairs are turned fully on, does more water per second flow out the downstairs faucet? Or is the volume of water flowing from the faucets the same?
More water will flow from a downstairs open faucet because of the greater pressure. Since pressure depends on depth, the downstairs faucet is effectively "deeper" than the upstairs faucet. The pressure downstairs is greater by an amount = weight density × depth, where the depth is the vertical distance between faucets.
119.If liquid pressure were the same at all depths, would there be a buoyant force on an object submerged in the liquid? Discuss your explanation with your friends.
No. The reason for a bouyant force is because pressure is depth dependent, This means that pressure is the gretaest on the bottom of all bodies. This in turn means that water pressure will push up on it the most which is the bouyant force. This is because pressure in a fluid is exeretd equallyin all directons at any point. If the presure was the same everywhere, there wpuld be no higher pressure pushing up, so you would have no bouyantforce
-Formula for Boyle's law
P1V1=P2V2
103. Say you've had a run of bad luck, and you slip quietly into a small, calm pool as hungry crocodiles lurking at the bottom are relying on Pascal's principle to help them to detect a tender morsel. What does Pascal's principle have to do with their delight at your arrival?
Part of whatever pressure you add to the water is transmitted to the hungry crocodiles, via Pascal's principle. If the water were confined, that is, not open to the atmosphere, the crocs would receive every bit of pressure you exert. But even if you were able to slip into the pool to quietly float without exerting pressure via swimming strokes, your displacement of water raises the water level in the pool. This ever-so-slight rise, and accompanying ever-so-slight increase in pressure at the bottom of the pool, is an eversowelcome signal to the hungry crocodiles. Yum! Yum!
-A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid.
Pascal's principle
-The ratio of force to the area over which that force is distributed:
Pressure
-A floating object displaces a weight of fluid equal to its own weight
Principle of flotation
101. Richard's pump can operate at a certain maximum well depth in Pocatello, Idaho. Would this maximum depth be greater than, less than, or the same as if he pumps water in San Francisco?
Richard's pump operates by way of atmospheric pressure. The greater the atmospheric pressure on the surface of water in the well, the deeper the well can be. Since atmospheric pressure is greater in sea-level San Francisco than in higher-altitude Pocatello, maximum well depth for Richard's pump is greater in San Francisco.
123.A balloon is weighted so that it is barely able to float in water. If it is pushed beneath the surface, does it rise back to the surface, stay at the depth to which it is pushed, or sink? Discuss your explanation. (Hint: Does the balloon's density change?)
The balloon will sink to the bottom because its density increases with depth. The balloon is compressible, so the increase in water pressure beneath the surface compresses it and reduces its volume, thereby increasing its density. Density is further increased as it sinks to regions of greater pressure and compression. This sinking is understood also from a buoyant force point of view. As its volume is reduced by increasing pressure as it descends, the amount of water it displaces becomes less. The result is a decrease in the initial buoyant force that was sufficient to barely keep it afloat.
91. A ship sailing from the ocean into a fresh water harbor sinks slightly deeper into the water. Does the buoyant force on it change? If so, does it increase or decrease?-
The buoyant force does not change. The buoyant force on a floating object is always equal to that object's weight, no matter what the fluid.
81. Why does an inflated beach ball pushed beneath the surface of water swiftly shoot above the water surface when released?
The buoyant force on the ball beneath the surface is much greater than the force of gravity on the ball, producing a large net upward force and large acceleration.
71. A can of diet soft drink floats in water, whereas a can of regular soft drink sinks. Discuss this phenomenon first in terms of density, then in terms of weight versus buoyant force.
The diet drink is less dense than water, whereas the regular drink is denser than water. (Water with dissolved sugar is denser than pure water.) Also, the weight of the diet can is less than the buoyant force that would act on it if totally submerged. So it floats, where buoyant force equals the weight of the can.
109.Two identical balloons of the same volume are pumped up with air to more than atmospheric pressure and suspended on the ends of a stick that is horizontally balanced. One of the balloons is then punctured. Is there a change in the stick's balance? If so, which way does it tip?
The end supporting the punctured balloon tips upwards as it is lightened by the amount of air that escapes. There is also a loss of buoyant force on the punctured balloon, but that loss of upward force is less than the loss of downward force, since the density of air in the balloon before puncturing was greater than the density of surrounding air.
79. How much force is needed to push a nearly weightless but rigid 1L carton beneath a surface of water?-
The force needed will be the weight of 1 L of water, which is 9.8 N. If the weight of the carton is not negligible, then the force needed would be 9.8 N minus the carton's weight, for then the Earth would be 'helping' to force the carton down.
89. One gondola in the Falkirk Wheel carries a 50 ton boat, while the opposite gondola carries a 100-ton boat. Why do the gondolas nevertheless weigh the same?-
The gondolas weigh the same because they're brim full, and whatever the weight of a floating boat, that same weight of water was displaced when the boat entered the gondola.
99. If you could somehow replace the mercury in a mercury barometer with a denser liquid, would the height of the liquid column be greater or less than with mercury? Why?
The height would be less. The weight of the column balances the weight of an equal-area column of air. The denser liquid would need less height to have the same weight as the mercury column.
107. When you replace helium in a balloon with hydrogen, which is less dense? Does the buoyant force on the balloon change if the balloon remains the same size? Explain.
The hydrogen-filled balloon is less dense. The buoyant force does not change because the volume of the balloon does not change. The buoyant force is the weight of air displaced, and doesn't depend on what is doing the displacing. The net upward force (BF − mg) is, however, greater on the lighter hydrogen balloon.
75. Stand on a bathroom scale and read your weight. When you lift one foot up so that you're standing on one foot, does the reading change? Does a scale read force or pressure?
The scale measures force, not pressure, and is calibrated to read your weight. That's why your weight on the scale is the same whether you stand on one foot or both.
93. Why is the pressure in an automobile's tires slightly greater after the car has been driven several kilometers?
The tires heat, giving additional motion to the gas molecules within the tires.
121.A barge filled with scrap iron is in a canal lock. If the iron is thrown overboard, does the water level at the side of the lock rise, fall, or remain unchanged? Discuss your explanation with your discussion group.
The water level will fall. This is because the iron will displace a greater amount of water while being supported than when submerged. A floating object displaces its weight of water, which is more than its own volume, while a submerged object displaces only its volume. (This may be illustrated in the kitchen sink with a dish floating in a dishpan full of water. Silverware in the dish takes the place of the scrap iron. Note the level of water at the side of the dishpan, and then throw the silverware overboard. The floating dish will float higher and the water level at the side of the dishpan will fall. Will the volume of the silverware displace enough water to bring the level to its starting point? No, not as long as it is denser than water.)
83. When a wooden block is placed in a beaker that is brim full of water, what happens to the scale reading after water has overflowed? Answer the same question for an iron block.
The weight on the scale doesn't change, for the weight of the brim-full beaker is the same whether or not a block floats in it, because the block's weight equals the weight of water that overflows ( Figure 5.16). But not so with an iron block that sinks in the water and is heavier than the water displaced. The reading increases when the iron block is in the beaker.
97. Why is there no atmosphere on the Moon?
There is no atmosphere on the Moon because the speed of a sizable fraction of gas molecules at ordinary temperatures exceeds lunar escape velocity (because of the Moon's smaller gravity). Any appreciable amounts of gas have long ago leaked away, leaving the Moon airless.
92. In a sporting goods store, you see what appear to be two identical life preservers of the same size. One is filled with Styrofoam and the other one with lead pellets. If you submerge these life preservers in the water, upon which is the buoyant force greater? Upon which is the buoyant force ineffective? Why are your answers different?
They have the same bouyant force because they are the same size and according to Archimede's principle, any body submerged in a fluid is bouyed up by a force equal to weight of luid the body disp[places. The bouyantb force is ineffective on th epreserver full of pellets becuse the rpeserver has more density due to the heavy pellets inside it. This makes it have more mass than the bouyant force cn push and it sinks to tyhe botom.
127.Two teams of eight horses each were unable to pull the Magdeburg hemispheres apart (Figure 5.20). Why? Suppose two teams of nine horses each could pull them apart. Then would one team of nine horses succeed if the other team were replaced with a strong tree? Discuss and defend your answer.
To begin with, the two teams of horses used in the Magdeburg hemispheres demonstration were for showmanship and effect, for a single team and a strong tree would have provided the same force on the hemispheres. So if two teams of nine horses each could pull the hemispheres apart, a single team of nine horses could also, if a tree or some other strong object were used to hold the other end of the rope.
98. We can understand how pressure in water depends on depth by considering a stack of bricks. The pressure below the bottom brick is determined by the weight of the entire stack. Halfway up the stack, the pressure is half, because the weight of the bricks above is half. To explain atmospheric pressure, we should consider compressible bricks, like foam rubber. Why is this so?
Unlike water, air is comrpeessible, so when air stacks on top of itself, it compresses the deeper you go, which is why air oressure is much greater than that of air pressure high up in the air
118.Suppose you wish to lay a level foundation for a home on hilly and bushy terrain. How can you use a garden hose filled with water to determine equal elevations for distant points?
Water seeks its own level from pressure. This means the heitght of water will be the same throughout. This mea s that when you law out the hose on th eground and therr eis a deeo spot, you will nptice the height of the water in the hose is lower. The same applies for a bump. If it goes oevr the bump, you will notice that there is no water on one side of the hose.
129.If you bring an airtight bag of potato chips aboard an airplane, you'll note that it puffs up as the plane ascends to high altitude. Why?
Whatever air is inside when on the ground expands against the decreased cabin pressure when the plane is aloft. Air pressure in the bag is then greater than the surrounding atmospheric pressure.
76. Why are people who are confined to bed less likely to develop bedsores on their bodies if they use a waterbed rather than a standard mattress?
When laying on a mattress, it is solid and only applies force upwards. When you lay on it, only parts of yur body are actaully tpuching it. This applies more pressure to those parts of your body, while some have less or no pressure applied to them at all. This causes bedsores. Waterbeds, on th eother hand, have you sink into them and pressure in a fluid at any point is exerted equally in all directions, so every part if your body is being pushed on by pressure.
85. Why does a volleyball that is held beneath the surface of water have more buoyant force than a volleyball that is floating?
When the ball is held beneath the surface, it displaces a greater weight of water.
125.When an ice cube in a glass of water melts, does the water level in the glass rise, fall, or remain unchanged? Does your answer change if the ice cube contains many air bubbles? Discuss whether or not your answer changes if the ice cube contains many grains of heavy sand.
When the ice cube melts the water level at the side of the glass is unchanged (neglecting temperature effects). To see this, suppose the ice cube is a 5-gram cube; then while floating it will displace 5 grams of water. But when melted it becomes the same 5 grams of water. Hence the water level is unchanged. The same occurs when the ice cube with the air bubbles melts. Whether the ice cube is hollow or solid, it will displace as much water floating as it will when melted. If the ice cube contains grains of heavy sand, however, upon melting, the water level at the edge of the glass will drop. This is similar to the case of the scrap iron of Question 116.
Lift is greater when there is
a large wing area and when the plane is traveling fast.
When liquid presses against a surface
a net force is directed perpendicular to the surface
liquid pressure is exerted ________- in alll directuons
equally
-Pressure Formula
force/area
132.Your study partner says he doesn't believe in Bernoulli's principle and cites as evidence the fact that a stream of water can knock over a building. The pressure that the water exerts on the building is not reduced, as Bernoulli claims. What distinction is your partner missing?
k
74. Which is more likely to hurt—being stepped on by a 200
lb man wearing loafers or being stepped on by a 100-lb woman wearing high heels?-74. It is more likely to hurt being stepped on a 100 lb woman wearing high heels than a 200 lb man wearing loafers. This is because of pressure. Pressure is the amount of force on a unit of area or the amount of force exerted on a certain amount of area. The formula for this is force divided by area. This means that the bigger the force, the bigger the pressure, and the bigger the area, the less amount of force. In this case, the man would exert more force on you with a force of 2,000 N, but his loafer has a lot more area, so that force is reduced a lot. This can be backed up by Pascal's principle when it states how if a change in pressure happens to a portion of an enclosed fluid at rest, it equally affects the entire fluid. This means that if you were you exert a ;large force over a small pressure plate that transmits to a large piston to push it up, the force would affect the large large with just as much exerted on the small pressure plate, but the pressure would be less because the force would have to split up to cover the entire piston, thereby making the force the same, but the pressure less. Back on the subject of the man's shoe, when he exerts that force, the force must split upt to cover the shoe's larger area, which will make the actual pressure on you less. Meanwhile, the 100lb lady has only a force of 1,000 N exerted on you, but she would have a larger pressure because her high heels have less area, which means the force doesn't have to split up as much to cover the whole area. This will mean that the pressure of the 1,000 N will be lowered only a little bit compared to the pressure of the 2,000 N loafers.
When the average pressure difference over the wing is multiplied by the surface area of the wing, we have a net upward forc
lift
3 metals less dense than watewr
lithium, sodium, pottatsium
110.The force of the atmosphere at sea level against the outside of a 10
m2 store window is about 1 million N. Why does this not shatter the window? Why might the window shatter in a strong wind blowing past the window?- Two different presures are pushing on the window formdifferent sides which balances things out. Shatters if a strong wind blows because that means it will have smaller pressure and therefore the otehr pressure will overpower it on the otehr side and break the window. BERNOULLI PRINCLE
what did Otto do
placed together two copper hemispheres about 0.5 m in diameter to form a sphere, as shown in Figure 5.20. He set a gasket made of a ring of leather soaked in oil and wax between them to make an airtight joint. When he evacuated the sphere with his vacuum pump, two teams of eight horses each were unable to pull the hemispheres apart.
124.Greta Novak is treated to remarkable flotation in the very
salty Dead Sea. How does buoyant force on her compare when she is floating in fresh water? In answering this question, discuss differences between the volumes of water displaced in the two cases.-124. The salt water has a greater buoyant force because it has a higher density than the fresh water one. This is because of Archimedes Principle which states that a body is buoyed up by a force equal to the weight of the furious displaced by the body. This means that while they both displace the same amount of fluid, the weights of the fluids differ. This means that the high salt water creates a higher density in the water and therefore gives it a bigger weight, so you rise a lot more compared to that of the freshwater and it's low density.
113.What physics principle underlies the following three observations? When passing an oncoming truck on the highway, your car tends to sway toward the truck. The canvas roof of a convertible automobile bulges upward when the car is traveling at high speeds. The windows of older passenger trains sometimes break when a high
speed train passes by on the next track.-All are Bernoulli's principle. For the moving car the pressure will be less on the side of the car where the air is moving fastest—the side nearest the truck, resulting in the car being pushed by the atmosphere towards the truck. Inside the convertible, atmospheric pressure is greater than outside, and the canvas rooftop is pushed upwards toward the region of lesser pressure. Similarly for the train windows, where the interior air is at rest relative to the window and the air outside is in motion. Air pressure against the interior surface of the window is greater than the atmospheric pressure outside. When the difference in pressures is large enough, the window is blown out.
87. Give a reason why canal enthusiasts in Scotland appreciate the physics illustrated in Figure 5.16 (the block of wood floating in a vessel brimfilled with water).-
the weight of a filled vessel of water is the same no matter what floats in it. -Figure 5.16 shows that the weight of a filled vessel of water is the same no matter what floats in it. This is the basis of the Falkirk Wheel in Scotland ( Figure 5.17).
126.Count the tires on a large tractor
trailer that is unloading food at your local supermarket, and you may be surprised to count 18 tires. Why so many tires? (Hint: See Activity 35.)-126. This is because of Pascal's Principle which states that if a change in pressure occurs in any part of a fluid, that change is transmitted to every part of that fluid. This means that if the tractor trailer had a normal amount of wheels, the weight of the cargo would apply too much pressure on the tires to get them moving and would just push them onto the ground. This way with more wheels, the force will be divided equally into each of them and thus, the pressure will be less, so the tractor trailer can get moving.
