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Physical science gerner Questions
What happens to the volume of a loaf of bread when it is squeezed? What happens to the mass? To the density? - verified answer Volume decreases masterminds and changed and density increases when the loaf is squeezed. Distinguish between for some pressure. Compare their units of measurement. - verified answer Force is a push or pull measured in newtons; pressures force per unit area measured in newtons per square meter How does the pressure exerted by a liquid change with a liquid how does the pressure exerted by a liquid changes the density of a liquid changes? - verified answer According to the formula, liquid pressure = density × depth, pressure increases with an increase in depth and/or an increase in density. How does water pressure 1m below the surface of a small pond compare to water pressure 1m below the surface of a huge lake? - verified answer Pressure at the same depth will be the same in the pond or the lake what does buoyant force act upward on an object submerged in water? - verified answer Buoyant force acts upward because pressure is greater up against the bottom where the water is deeper state Archimedes principle - verified answer An immersed body is buoyed up by a force equal to the weight of the fluid displaced. does the buoyant force on a floating object depend on the weight of the object or on the weight of the fluid displaced by the object? Or are these two weights the same for the special case of floating? Defend your answer. - verified answer In the special case of floating, both buoyant force and the weight of the floating object are the same. In all cases, buoyant force equals the weight of fluid displaced. what weight of water is displaced by a 100-ton floating ship? What is the buoyant force that acts on this ship? - verified answer 100 tons of water are displaced by a 100-ton floating ship. Buoyant force on the ship is therefore 100 tons. how does the weight of mercury in a barometer tube compare with the weight of an equal cross- section of air from sea level to the top of the atmosphere? - verified answer Both weights are the same.
what happens to the pressure in all parts of a confined fluid when the pressure in one part is increased? - verified answer An increase in pressure in one part of a confined fluid is transmitted throughout the fluid to all parts does pascals principle provide a way to get more energy from a machine that is put into it? - verified answer No! No machine can do that. Pascal's principle provides a way to multiply force (at the expense of distance). a balloon that weighs 1 N is suspended in air, drifting neither up nor down. How much buoyant force acts on it? What happens f the buoyant force decreases? Increases? - verified answer When the balloon is in equilibrium, buoyant force equals its weight, 1 N. If the buoyant force increases, the balloon will rise. Does Bernoullis principle refer to internal pressure change in a fluid, or to pressures that a fluid can exert on objects in the path of the flowing fluid? Or both? - verified answer Bernoulli's principle refers only to the internal pressure changes in a fluid; not to pressures the fluid may exert when it interacts with objects in the path of the fluid What do peaked roofs, convertible tops and airplane wings have in common when air moves fastest across their top surface? - verified answer When air speeds up in passing over these surfaces, streamlines become more crowded and air pressure at the surfaces decreases. All three experience a "lift." Rank the following from highest to lowest percentage of its volume above the waterline: (a) basketball floating in fresh water, (b) basketball floating in salt water, and (c) basketball floating in mercury. - verified answer C, B, A. Rank the buoyant force supplied by the atmosphere on the following, from greatest to least (a) an elephant, (b) a helium-filled party balloon and (c) a skydiver at terminal velocity. - verified answer A, C, B You know that a sharp knife cuts better than a dull knife. Do you know why this is so? Defend your answer. - verified 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
in a classroom demonstration a vacuum pump evacuates air from a large empty oil drum, which slowly and dramatically crumples as shown in the photo. A student friend says that the vacuum sucks in the sides of the drum. What is your explanation? - verified answer It is more correct to say that the atmosphere pushes in the sides of the barrel. It is able to do this because of the low air pressure in the barrel. Things push; nothing sucks if you bring a bag of potato chips aboard an airplane, youll note that the unopened bag puffs up as the plane ascends to high altitude. Why? And why is this effect opposite to what happens to the drum in the preceding question? - verified answer Assuming the bag is airtight, whatever air is inside when on the ground expands against the decreased cabin pressure when the plane it aloft. Air pressure in the bag > surrounding atmospheric pressure. In the case of the crunched drum in the previous question, the surrounding air has more pressure than whatever air remains inside the barrel. Opposite results for opposite situations. 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 position to raise the 10 kg that rest on the small piston. Do you think he will be successful? Defend your answer. - verified answer The strong man will be unsuccessful. He will have to push with 50 times the weight of the 10 kilograms. That's 5000 N, more than his weight. The hydraulic arrangement is arranged to his disadvantage. Ordinarily, the input force is applied to the smaller piston and the output force to the large piston. This arrangement is just the opposite. invoking ideas from Chapter 2 and this chapter, discuss why is it esier to throw a curve with a tennis ball than a baseball. - verified answer. A tennis ball has about the same size as a baseball, but much less mass. Less mass means less inertia, and more acceleration for the same force, as discussed in Chapter 2. A Ping-Pong ball provides a more obvious curve due to spinning (Chapter 5) because of its low mass. is the temperature of an object a measure of the total translational kinetic energy of molecules in the object or a measure of the average translational kinetic energy per molecules in the object? - verified answer Temperature is a measure of the average translational KE per molecule how much energy can be removed from a system at 0 k? - verified answer No energy can be removed from a system at 0 K. in which direction does thermal energy flow between hot and cold objects? - verified answer Energy transfers from warmer objects to cooler objects how does heat differ from thermal energy? - verified answer Heat is thermal energy that flows from hot to cold locations.
what role does temperature play in the direction of thermal energy flow? - verified answer The direction of thermal energy flow is from objects at higher temperatures to lower temperatures. which law of thermodynamics is the conservation of energy applied to thermal systems? - verified answer The first law of thermodynamics is in accord with energy conservation. what happens to heat added to a system that doesn't increase the temperature of the system? - verified answer Added heat that doesn't raise temperature increases the thermal energy of the system and/or does external work if it leaves the system. which law of thermodynamics reltes to the direction of heat flow? - verified answer The second law of thermodynamics relates to the direction of heat flow when can thermal energy in a system move from lower to higher temperature? - verified answer Thermal energy can move from lower to higher temperatures only when external work is done on the system. which law of thermodynamics relates to a system reaching 0 k? - verified answer The third law states that no system can reach absolute zero. when disorder in a system increases, does entropy increase or decrease? - verified answer Entropy is a measure of disorder, and the more disorder, the more the entropy. So entropy increases with disorder in a system under what condition can the entropy of a system be decreased? - verified answer The entropy of a system decreases when work is put into it how does the specific heat capacity of water compare with the specific heat capacities of other common materials? - verified answer Water has an appreciably higher specific heat capacity than other common materials. why does a bimetallic strip bend with changes in temperature? - verified answer The strip bends due to its two metals with difference rates of thermal expansion.
a metal ball is barely able to apss through a metal ring. When Anette Zetterberg heats the ball, it does not pass through the ring. What happens if she insread heats the ring: does the size of the hole increase, stay the same, or decrease? - verified answer Every part of a metal ring expands when it is heated—not only the thickness, but the outer and inner circumference as well. Hence the ball that normally passes through the hole when the temperatures are equal will more easily pass through the expanded hole when the ring is heated. (Interestingly, the hole will expand as much as a disk of the same metal undergoing the same increase in temperature. Blacksmiths mounted metal rims in wooden wagon wheels by first heating the rims. Upon cooling, the contraction resulted in a snug fit.)
. why cant you tell whether you are running a fever by touvhing your own forehead? - verified answer There would be no temperature difference between your hand and forehead. If your forehead is a couple of degrees higher in temperature than normal, then your hand is also a couple of degrees higher. which of he laws of thermodynamics says what doesn't happen? - verified answer Only the second law is a probabilistic statement and has exceptions on cold winter nights in days past, it was common to bring a hot object to bed with you. Which would keep you warmer through the cold night: a 10-kg iron bring or a 10-kg iron brick or a 10-kg jug of hot water at the same high temperate? Explain. - verified answer The brick will cool off too fast and you'll be cold in the middle of the night. Bring a jug of hot water with its higher specific heat to bed and you'll make it through the night. why does the prescence of large bodies of water tend to moderate the climate of nearby land- making it warmer in cold weather and cooler in hot weather? - verified answer In winter months when the water is warmer than the air, the air is warmed by the water to produce a seacoast climate warmer than inland. In summer months when the air is warmer than the water, the air is cooled by the water to produce a seacoast climate cooler than inland. This is why seacoast communities and especially islands do not experience the high and low temperature extremes that characterize inland locations. entropy is a measure of how enrgy spreads to disorder in a system. Disorder increases and entropy increases. How does this relate to opening a bottle of perfume in the corner of a room? - verified answer The natural state of the perfume molecules is to spread out, a state of higher probability, and a state of increasing entropy. Perfume molecules and their smell will soon drift to all parts of the room. in the preceding question, we see a reason why all the gas molecules in our room don't suddenly rush to one corner, leaving us sitting in a vacuum and gsping for breath. Does the fact that air naturally spreads out mean that entropy increases or decreases? - verified answer Entropy increases, for spreading around maximizes the disorder of molecules.
if cooling occurred at the bottom of a pond instead of at the surface, would a lake freeze from the bottom up? Explain. - verified answer If cooling occurred at the bottom of a pond instead of at the surface, ice could still form at the surface, but it would take much longer for ponds to freeze. This is because all the water in the pond would have to be reduced to a temperature of 0°C rather than 4°C before the first ice would form. Ice that forms at the bottom where the cooling process occurs would be less dense and would float to the surface (except for ice that may form on material anchored to the bottom of the pond). What is the role of "loose" electrons in hear conductors? - verified answer Loose electrons quickly move and transfer energy to other electrons that migrate through the material. by what means heat transferred by convection? - verified answer Heat is transferred by the movement of fluids. what happens to the temperature of air when it expands? - verified answer Expanding air cools. So temperature is reduced. why isn't Millie's hand burned when she holds it above the escape valve of the pressure cooker? - verified answer Her hand is not in steam, but in a jet of condensed vapor that has expanded and cooled. how does the paek frequency of raiant energy relate to the absolute temperature of the radiating source? - verified answer Peak frequency and absolute temperature are directly proportional: f T because all objects emit energy to their surroundings, why don't the temperatures fall objects continuously decrease? - verified answer Temperatures don't continuously decrease because all object are also absorbing radiant energy. why does the pupil of the eye appear black? - verified answer The pupil appears black because light that enters the eye doesn't exit. With flash cameras, however, some of it does why undergoes a faster rate of cooling: a red-hot poker in a warm oven or a red-hot poker in a cold room? - verified answer By Newton's law of cooling, the hot poker in the cold room radiates more due to the greater temperature difference between the poker and the room.
from best to worse, rank these materials as heat conductors: (a) copper wire, (b) snow and a (c) glass rod. - verified answer A, C, B. what is the purpose of the copper or aluminum layer on the bottom of a stainless steel pot? - verified answer Copper and aluminum are better conductors than stainless steel, and therefore transfers heat more quickly to the pot's interior. in terms of physics, why do restaraunts serve baked potatoes weapped in aluminum foil? - verified answer Wrapping the potatoes in aluminum foil mainly retains the heat after the potatoes are removed from the oven. Also, heat transfer by radiation is minimized as radiation from the potatoes is internally reflected; heat transfer by convection is minimized as circulating air cannot make contact with the shielded potatoes. The foil also serves to retain moisture. many tongues have been injured by licking a piece of metal on a very cold day. Why would no harm result if a piece of wood were licked on the same day? - verified answer In touching the tongue to very cold metal, enough heat can be quickly conducted away from the tongue to bring the saliva to sub-zero temperature where it freezes, locking the tongue to the metal. In the case of relatively nonconducting wood, much less heat is conducted from the tongue and freezing does not take place fast enough for sudden sticking to occur wood is a better insulator than glass, yet fiberglass is commonly used as an insulator in wooden buildings, explain. - verified answer Air is an excellent insulator. The reason that fiberglass is a good insulator is principally because of the vast amount of air spaces trapped in it. wood hs a very low conductivity. Does it still have a low conductivity if it is very hot- that is, in the stage of smoldering red-hot coals? Could you safely walk across a bed of red-hot wooden coals with bare feet? Although the coals are hot, does much heat conduct from them to your feet It you step quickly? Could you do the same on pieces of red-hot iron? explain - verified answer The conductivity of wood is relatively low whatever the temperature—even in the stage of red-hot coals. You can safely walk barefoot across red-hot wooden coals if you step quickly because very little heat is conducted to your feet. Because of the poor conductivity of the coals, energy from within the coals does not readily replace the energy that transfers to your feet. This is evident in the diminished redness of the coal after your foot has left it. Stepping on red-hot iron coals, however, is a different story. Because of the excellent conductivity of iron, large amounts of heat would injure your feet. Ouch! what does the high specific heat capacity of water have to do with the convection currents in the air at the seashore? - verified answer Because of the high specific heat of water, sunshine warms water much less than it warms land. As a result, air is warmed over the land and rises. Cooler air from
above the cool water takes its place and convection currents are formed. If land and water were heated equally by the Sun, such convection currents (and the winds they produce) wouldn't occur snow-making machines used at ski areas blow a mizture of compressed air and water rhrought a muzzle. The temperature of the mixture may initially be well above the freezing temperature of water, yet crystals of sow are formed as the mixture is ejected from the nozzle. Explain how this happens. - verified answer The mixture expands when it is ejected from the nozzle, and therefore cools. At the freezing temperature of 0°C, ice forms. the source of heat of volcanoes and natural hot springs is trace amounts of radioactive minerals in common rock in earths interior. Why isn't the same kind of rock at earths surface warm to touch? - verified answer The energy given off by rock at the Earth's surface transfers to the surroundings practically as fast as it is generated. Hence there isn't the buildup of energy that occurs in the Earth's interior. why is a water-based wire solution, whitewash, sometimes applied to the glass of florists greenhouse? Would you expect this practice to be more prevalent in winter or summer months? - verified answer When it is desirable to reduce the radiant energy coming into a greenhouse, whitewash is applied to the glass simply to reflect much of the incoming sunlight. Energy reflected by the greenhouse is energy not absorbed. if the composition of the upper atmosphere were changed to permit a greater amount of terrestrial radiation to escape, what effect would this have on earth climate? - verified answer If more terrestrial radiation in the upper atmosphere escaped, Earth's climate would be cooler why does wrapping a bottled beverage in a wet cloth at a picnic often produce a cooler bottle than placing the bottle in a bucket of cold water? - verified answer A bottle wrapped in wet cloth will cool by the evaporation of liquid from the cloth. As evaporation progresses, the average temperature of the liquid left behind in the cloth can easily drop below the temperature of the cool water that wet it in the first place. So to cool a bottled beverage at a picnic, wet a piece of cloth in a bucket of cool water, then wrap it around the bottle. As evaporation progresses, the temperature of the water in the cloth drops, and cools the bottle to a temperature below that of the water in the bucket room-temperature of water boils spontaneously in a vacuum- on the moon, for example. Could you cook an egg in this boiling water? Explain. - verified answer You could not cook food in low- temperature water that is boiling by virtue of reduced pressure. Food is cooked by the high temperature it is subjected to, not by the bubbling of the surrounding water. For example, put room-temperature water in a vacuum and it will boil. But this doesn't mean the water will transfer more thermal energy to an egg than before boiling—an egg in this boiling water won't cook at all!
you are ready to drink it? This question should elicit much discussion! - verified answer Pour the cream in right away for at least three reasons. Since black coffee radiates more heat than white coffee, make it whiter right away so it won't radiate and cool so quickly. Also, by Newton's law of cooling, the higher the temperature of the coffee above the surroundings, the greater will be the rate of cooling—so again add cream right away and lower the temperature to that of a reduced cooling rate, rather than allowing it to cool fast and then bring the temperature down still further by adding the cream later. Also—by adding the cream, you increase the total amount of liquid, which for the same surface area, cools more slowly. earth scientist are considering a means of inducing clouds to be a brighter white. What effect would it have on earths climate? - verified answer More solar energy would be reflected into space, cooling Earth's surface beneath. (Whitening clouds is a consideration in offsetting the warming by excess carbon dioxide.) why is a tub of water placed in farmer canning cellar in cold winter to help prevent canned food from freezing? - verified answer Every gram of water that undergoes freezing releases 80 calories of thermal energy to the cellar. This continual release of energy by the freezing water keeps the temperature of the cellar from going below 0°C. Sugar and salts in the canned goods prevent the canned goods from freezing at 0°C. Only when all the water in the tub freezes will the temperature of the cellar go below 0°C and then freeze the canned goods. The farmer must, therefore, replace the tub before or just as soon as all the water in it has frozen. why does spraying fruit trees with water before a frost help protect the fruit from freezing? - verified answer The answer is similar to the previous answer, and also the fact that the coating of ice acts as an insulating blanket. Every gram of water that freezes releases 80 calories, much of it to the fruit; the thin layer of ice then acts as an insulating blanket against further loss of heat. the snow-covered mailboxes raise a question: what physics explains why the light-colored ones are snow covered, while the black ones free of snow? - verified answer The black boxes, better absorbers, are somewhat warmer in sunlight or even an overcast day than the lighter boxes, so snow is more likely to melt upon the black surfaces than the lighter ones. Hence the accumulation of snow on the lighter mailboxes.
