Physical science gerner

what happens to heat added to a system that doesn't increase the temperature of the system?

Added heat that doesn't raise temperature increases the thermal energy of the system and/or does external work if it leaves the system.

wood is a better insulator than glass, yet fiberglass is commonly used as an insulator in wooden buildings, explain.

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.

why undergoes a faster rate of cooling: a red-hot poker in a warm oven or a red-hot poker in a cold room?

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.

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.

C, B, A.

invoking ideas from Chapter 2 and this chapter, discuss why is it esier to throw a curve with a tennis ball than a baseball.

. 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.

what weight of water is displaced by a 100-ton floating ship? What is the buoyant force that acts on this ship?

100 tons of water are displaced by a 100-ton floating ship. Buoyant force on the ship is therefore 100 tons.

what happens to the temperature of air when it expands?

Expanding air cools. So temperature is reduced.

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?

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

does a gas release energy or absorb energy when it changes in a liquid? How about a solid changing into a liquid?

A gas gives off energy when changing to a liquid; when solid changes to a liquid it absorbs energy.

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

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.

A, C, B

from best to worse, rank these materials as heat conductors: (a) copper wire, (b) snow and a (c) glass rod.

A, C, B.

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?

According to the formula, liquid pressure = density × depth, pressure increases with an increase in depth and/or an increase in density.

state Archimedes principle

An immersed body is buoyed up by a force equal to the weight of the fluid displaced.

what happens to the pressure in all parts of a confined fluid when the pressure in one part is increased?

An increase in pressure in one part of a confined fluid is transmitted throughout the fluid to all parts

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?

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.

what does the high specific heat capacity of water have to do with the convection currents in the air at the seashore?

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

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?

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 physics principle underlies the following three observation? When passing an oncoming truck on the highway, your car tends to sway toward the truck. The canvas roof of a convertible car 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.

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's being pushed by the atmosphere towards the truck. Inside the convertible, atmospheric pressure is greater than outside, and the canvas rooftop is pushed upwards towards 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 significant enough, the window is blown out.

when a 1-kg pan containing 1 kg of cold water is removed from the refrigerator onto a table, which absorbs more heat from the room: the pan or the water?

Both the pan and water undergo the same temperature change. But water, with its greater specific heat capacity, absorbs more heat.

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?

Both weights are the same.

what does buoyant force act upward on an object submerged in water?

Buoyant force acts upward because pressure is greater up against the bottom where the water is deeper

what is condensation, how does it differ from evaporation and why is it a warming process?

Condensation is the opposite of evaporation. Gas molecules near a liquid surface are attracted to the liquid, strike it with increased KE, and thereby warm the liquid.

when boiling spaghetti, is your cooking time reduced if the ater is vigourosly boiling instead of gently boiling?

Cooking time will be no different for vigorously boiling water and gently boiling water, for both have the same temperature. The reason spaghetti is cooked in vigorously boiling water is simply to ensure the spaghetti doesn't stick to itself and the pot. For fuel economy, stir your spaghetti in gently boiling water.

what is the purpose of the copper or aluminum layer on the bottom of a stainless steel pot?

Copper and aluminum are better conductors than stainless steel, and therefore transfers heat more quickly to the pot's interior.

would it be slightly more difficult to draw soda through a straw at sea level or on top of a very high mountain? Explain.

Drinking through a straw is slightly more difficult atop a mountain. This is because the reduced atmospheric pressure is less effective in pushing soda up into the straw

in which direction does thermal energy flow between hot and cold objects?

Energy transfers from warmer objects to cooler objects

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?

Entropy increases, for spreading around maximizes the disorder of molecules.

when disorder in a system increases, does entropy increase or decrease?

Entropy is a measure of disorder, and the more disorder, the more the entropy. So entropy increases with disorder in a system

distinguish between evaporation and boiling.

Evaporation is a phase change at the surface of a liquid; boiling is a phase change that occurs throughout a liquid, producing bubbles

what is evaporation and why is it a cooling process?

Evaporation is the change of phase from liquid to gas. As fast-moving molecules in a liquid escape into the air, slower ones on average are left behind, thereby cooling the water.

why is a tub of water placed in farmer canning cellar in cold winter to help prevent canned food from freezing?

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.

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?

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.)

you come into a crowded chilly classroom early in the morning on a cold winter day. Before the end of the hour, the room temperature increase to comfortable level, even if heat is not provided by the heating system. Why the difference?

Every student radiates about the same amount of heat as a 100-W incandescent bulb. So heat radiated by you and your classmates increases the temperature of the room.

Distinguish between for some pressure. Compare their units of measurement.

Force is a push or pull measured in newtons; pressures force per unit area measured in newtons per square meter

how does heat differ from thermal energy?

Heat is thermal energy that flows from hot to cold locations.

by what means heat transferred by convection?

Heat is transferred by the movement of fluids.

why isn't Millie's hand burned when she holds it above the escape valve of the pressure cooker?

Her hand is not in steam, but in a jet of condensed vapor that has expanded and cooled.

what is the reason ice is less dense than water?

Ice is less dense than water due to its ice crystals that have open structures.

if cooling occurred at the bottom of a pond instead of at the surface, would a lake freeze from the bottom up? Explain.

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).

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?

If more terrestrial radiation in the upper atmosphere escaped, Earth's climate would be cooler

in terms of thermal expansion, why is it important that a lock and its key be made of the same or similar materials?

If they expanded differently, as for different materials, the fit between the lock and key wouldn't match.

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.

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.

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?

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

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?

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.

which of he laws of thermodynamics says what doesn't happen?

Only the second law is a probabilistic statement and has exceptions

how does the paek frequency of raiant energy relate to the absolute temperature of the radiating source?

Peak frequency and absolute temperature are directly proportional: f T

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?

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

which generally expands more for an equal increase in temperature: solid or liquids?

Liquids generally expand more for equal increases in temperature

What is the role of "loose" electrons in hear conductors?

Loose electrons quickly move and transfer energy to other electrons that migrate through the material.

why does increasing the temperature of a solid make it melt?

Molecular motion increases and molecules shake apart with increasing temperature.

does a liquid release energy or absorb energy when it changes into a gas? When it changes into a solid?

Molecular motion slows allowing molecules to bind together

why does decreasing the temperature of a liquid make it freeze?

Molecular motion slows allowing molecules to bind together

earth scientist are considering a means of inducing clouds to be a brighter white. What effect would it have on earths climate?

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.)

how much energy can be removed from a system at 0 k?

No energy can be removed from a system at 0 K.

air-conditioning units contain no water whatever, yet it is common to see water dripping from operating air conditioners poking outside homes on a hot day. Explain.

No water leaks from inside the unit, for water vapor in warm air condenses on its low-temperature metal surface. That's the water that drips.

does pascals principle provide a way to get more energy from a machine that is put into it?

No! No machine can do that. Pascal's principle provides a way to multiply force (at the expense of distance).

why is it so difficult to breather when snorkeling at a depth of 1 m, and practically impossible at a depth of 2m? why cant a diver simply breathe through a hose that extends to the surface?

One's lungs, like an inflated balloon, are compressed when submerged in water, and the air within is compressed. Air will not of itself flow from a region of low pressure into a region of high pressure. The diaphragm in one's body reduces lung pressure to permit breathing, but this limit is strained when nearly 1 m below the water surface. The limit is exceeded at more than 1-m deep.

suppose that, at a restaurant you are served coffee before you are ready to drink it. In order that it is the hottest when you are ready for it, would you be wiser to add cream to it right away just before you are ready to drink it? This question should elicit much discussion!

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.

How does water pressure 1m below the surface of a small pond compare to water pressure 1m below the surface of a huge lake?

Pressure at the same depth will be the same in the pond or the lake

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?

Pressure would be appreciably greater by the woman, which would hurt you more.

desert san is very hot in the day and very cool at night. What does this tell you about its specific heat capacity?

Sand has a low specific heat, as evidenced by its relatively large temperature changes for small changes in thermal energy. A substance with a high specific heat, on the other hand, must absorb or give off large amounts of thermal energy for comparable temperature changes.

why is a steam burn more damaging than a burn from boiling water of the same temperature?

Steam has considerably more energy than boiling water of the same temperature.

what is sublimation?

Sublimation is the direct change of phase from solid to gas, skipping the liquid phase.

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?

Temperature is a measure of the average translational KE per molecule

because all objects emit energy to their surroundings, why don't the temperatures fall objects continuously decrease?

Temperatures don't continuously decrease because all object are also absorbing radiant energy.

on which temperature scale does the average kinetic energy of molecules double when the temperature doubles?

The Kelvin temperature scale.

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.

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.

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

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 role does temperature play in the direction of thermal energy flow?

The direction of thermal energy flow is from objects at higher temperatures to lower temperatures.

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?

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.

under what condition can the entropy of a system be decreased?

The entropy of a system decreases when work is put into it

what is the principle reason a feather quilt is so warm on a cold winter night?

The feather quilt is an excellent insulator (poor conductor), which slows the transfer of heat from your body to the surroundings.

which law of thermodynamics is the conservation of energy applied to thermal systems?

The first law of thermodynamics is in accord with energy conservation.

when you are near an incandescent lamp, tune it on and off quickly. You feel its hear, but you find when you touch the bulb that it is not hot. Explain why you felt hear from the lamp.

The heat you received was from radiation, which travels at the speed of light. Heating the glass, however, is a longer process.

which has the greater amount of thermal energy: an iceberg or a cup of coffee? Defend your answer.

The hot coffee has a higher temperature, but not a greater thermal energy. Although the iceberg has less thermal energy per mass, its enormously greater mass gives it a greater total energy than that in the small cup of coffee.

why does putting a lid over a pot of water on a stove shorten the time needed for the water to come to a boil, whereas, after the water boils, the suse of the lid only slightly shorten the cooking time.

The lid on the pot traps heat, which quickens boiling; the lid also slightly increases pressure on the boiling, water which raises its boiling temperature. The hotter water correspondingly cooks food in a shorter time, although the effect is not significant unless the lid is held down as on a pressure cooker.

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.

The mixture expands when it is ejected from the nozzle, and therefore cools. At the freezing temperature of 0°C, ice forms.

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?

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.

why does the pupil of the eye appear black?

The pupil appears black because light that enters the eye doesn't exit. With flash cameras, however, some of it does

which law of thermodynamics reltes to the direction of heat flow?

The second law of thermodynamics relates to the direction of heat flow

why does a bimetallic strip bend with changes in temperature?

The strip bends due to its two metals with difference rates of thermal expansion.

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.

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.

which law of thermodynamics relates to a system reaching 0 k?

The third law states that no system can reach absolute zero.

. why cant you tell whether you are running a fever by touvhing your own forehead?

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.

when can thermal energy in a system move from lower to higher temperature?

Thermal energy can move from lower to higher temperatures only when external work is done on the system.

What happens to the volume of a loaf of bread when it is squeezed? What happens to the mass? To the density?

Volume decreases masterminds and changed and density increases when the loaf is squeezed.

how does the specific heat capacity of water compare with the specific heat capacities of other common materials?

Water has an appreciably higher specific heat capacity than other common materials.

State an exception to the claim that all substances expand when heated.

Water is an exception. Between 4°C and 0°C, water expands when cooled.

What do peaked roofs, convertible tops and airplane wings have in common when air moves fastest across their top surface?

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."

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?

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.

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?

When the balloon is in equilibrium, buoyant force equals its weight, 1 N. If the buoyant force increases, the balloon will rise.

for many years a method for breaking boulders was putting them in a hot fire and then dousing them with cold water. Why did this fracture the boulders?

When the boulders are doused, the outer part of the boulders cools while the insides are still hot. This causes a difference in contraction, which fractures the boulders.

why is it inaccurate to say that heavy objects sink and light objects float? Give exaggerated examples to support your answer.

Whether an object sinks or floats has to do with density, not weight. A heavy piece of wood will float whereas a light piece of solid iron will sink; a log floats while a paper clip sinks in water.

what would be the consequence to Earths climate if the greenhouse effect were completely eliminated?

With no greenhouse effect Earth would be a very cold place, with an average temperature about −18°C.

in terms of physics, why do restaraunts serve baked potatoes weapped in aluminum foil?

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.

does Newtons law of cooling apply to warming as well as to cooling?

Yes, Newton's law of cooling also applies to warming.

your friend says that the buoyancy 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?

You agree with your friend, for the elephant displaces far more air than a small helium-filled balloon, or any small item. The effects of the buoyant forces, however, is a different story. The large buoyant force on the elephant is insignificant relative to its enormous weight. The tiny buoyant force acting on the balloon of tiny weight, however, is significant.

when cam you add heat to a substance without raising its temperature? Give an example.

You can add heat without raising temperature when the substance is undergoing a change of phase. Small amounts of heat added to 0°C ice, or to 100°C water, for example, doesn't increase temperature

room-temperature of water boils spontaneously in a vacuum- on the moon, for example. Could you cook an egg in this boiling water? Explain.

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!