Conceptual Physics Chapter 11-18 Class Questions

Why I and not H?

Because the way it would be installed/utilized would be the I.

Water pressure provided by a water tower is greater if the tower : is taller, holds more water, both, none

Is taller; only depth/height , not the amount of water contributes to the pressure

Why does the suspended spring stretch more at the top than at the bottom?

Less spring mass pulls at the bottom part, whereas the entire mass pulls on the top

What is the color of my bottle? Why? What do you notice on the outside of the bottle?

The air surrounding the bottle is cooler and this slows down the molecules around and therefore it creates dew

At ground level, the ballon is partially inflated. The same balloon is fully inflated at high altitudes BECAUSE

The bag of chip concept. The higher it goes the pressure outside will be less and the inside of the ballon will be more.

The atoms that constitute your body are mostly empty space, and structures such as the chair you're sitting on are composed of atoms that are also mostly empty space.So why don't you fall through the chair?

The electron cloud of the atoms that are neutral repel each other.

How does a microwave work?

The microwave tunes into the water via radiation. The water jiggles which causes friction which heats things up

The top part of a beam is stretched and the bottom part is compressed. What happens in the middle portion, between the top and bottom.

The middle part is neutral since both ends are extremes then the middle must be the neutral territory

Beaker full of water and then a beaker with the wooden block on it. Why does the reading of the balance not change?

(Look for if it submerged or floating THIS WILL MAKE THE DIFFERENCE!!!) This is floating, the reason is because there is a buoyant force acting on it. The force is equal to the weight of the displaced force which is the reason why the scales read the same.

A 2kg antique painting is hung from a spring. The spring stretches a distance of 10cm. If instead, a 4kg painting is hung from the same spring, how much will the spring stretch? If a 6kg painting is hung from the same spring

- A 4kg has twice the wright of a 2kg load. In accord with Hooke's law, F~Δx, 2 times the applied force results in 2 times the stretch, so the spring stretches 20cm.The weight of the 6kg load makes the spring stretch 3 times as far , 30cm

If your chilly outside the shower stall, step back inside and be warmed by the condensation of the excess water vapor.

- As steam condenses out it releases energy and heats up the shower stall - Water molecules tend to stick together. Because of their normally high average speed in air, however, most water molecules do not stick together when they collide. Instead, these fast-moving molecules bounce back when they collide and therefore remain in the gaseous phase. Some water molecules move more slowly than average, though, and these slow ones are more likely to stick to one another upon collision.

Two life preservers have identical volumes, but one is filled with Styrofoam while the other is filled with sand. When the two life preservers are fully submerged, the buoyant force is greater on the one filled with: Styrofoam, sand, same on each as long as their volumes are the same

- Both of them are identical, therefore they are displacing the same amount of water. They are therefore the same (key word is FULLY SUBMERGED) - Buoyant force is greatest on a submerged: 1-cubic centimeter block of aluminum, 1-cubic centimeter block of lead, is the same on each - SAME; they are submerged; they are same volume

The filling of pie is hot even though its crust is cool. Why?

- Different materials require different quantities of heat to raise the temperature of a given mass of the material by a specified number of degrees. - The specific heat capacity of any substance is defined as the quantity of heat required to change the temperature of a unit mass of the substance by 1 degree

How can an airplane fly?

- For the airplane it has to be shaped in a certain form. The air over the top has to flow faster than the bottom. Less pressure on the top then the bottom. Has a force pushing upward that lets it lift. - Shape the wing is such a way that the air has to travel a longer distance over the top than the bottom. The thing that goes in must go out. Therefore less pressure on top and this allows for the lift.

When water freezes, it expands. What does this say about the density of ice compared with the density of water? Do ice cubes float? What's the deal with icebergs?

- Ice is less dense than water (because it has more volume for the same mass), which is why ice floats on water. - Yes. Most of the iceberg is actually underwater.

Touch the inside of a 200C hot oven and you burn yourself. But when the 1800C white hot spark from a 4th of July type sparkler hit your skin. Your okay, why?

- Metal and air, insulator and conductor. The reason you survive is the difference between temperature, (average kinetic energy), which is determined by how much stuff is there; one of the sparklers is minuscule in comparison to you touching the entire surface of the oven. - Temperature is proportional to energy per molecule. How much energy depends on how many molecules. When you touch the inside surface of the oven you making contact with many many molecules and the flow of energy.

Why are airplanes shaped the way they are?

- The best ratio for volume is a sphere but they do not fly well so we use a cylinder type shape which allows for the effect when you fly. - Airplanes — like submarines are basically cylinders. They are shaped this way to survive large pressure.

A 1-L container completely filled with lead has a mass of 11.3 kg and is submerged in water. What is the buoyant force acting on it?

- The buoyant force equals the weight of the liter of water displaced—not the weight of the lead! One L of water has a mass of 1kg and weighs 10N. So the buoyant force on it is 10N - BECAUSE IT IS COMPLETELY SUBMERGED ;

Surface pressure is always perpendicular

- The reason why the water on the bottom can come out faster then the water at the top (imagine a cup with small holds along side) is because there is more pressure - The greater pressure against the bottom of a submerged object produced upward by the buoyant force

Two lakes; one is long but shallow, the other is short but deep. Which one exerts the larger pressure on the dam?

- The shorter one does; the reason is because it has more pressure (based off the fact that it has more depth) - The average water pressure acting against the dam depends on the average depth of the water and not on the volume of water held back. The large, shallow lake exerts only one-half the average pressure that the small, deep pond exerts. P=pgh

Is the piston that supports the load pulled up or pushed up?

- When you push it against something you are getting rid of the air through the vacuum and therefore the atmosphere pushes against this thing and it keeps that seal and creates that 'suction' effect - Produces a vacuum on one side and atmospheric pressure on the other side; if you destroy the seal than it falls to the ground

Entropy

- order to chaos; It is a measure of the amount of disorder in a system.

Which block exerts the larger pressure on the table? One standing or one laying down?

-The one that sits upright is same force over less area and therefore more pressure than the one going over a larger distance.

Pascal's principle

A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid. (Incompressible fluid is how hydraulics work)

A hydrogen and a carbon atom move at the same speed. Which has the greater kinetic energy?

A hydrogen has amu of 1 and carbon has amu of 12

A poor conductor of heat is a INSULATOR. They are one in the same.

Air is poor conductor. Metal is a good conductor.

Alcohol evaporates more quickly than water at the same temperature. Which produces more cooling—alcohol or the same amount of water on your skin?

Alcohol because it evaporates more quickly and reaches lower kinetic energy which equates to more cooling.

Ethyl alcohol has about on-half the specific heat capacity of water. If equal masses of each at the same temperature are supplied with equal quantities of heat, which will undergo the greater change in temperature?

Alcohol, for less specific heat means less thermal inertia and a greater change in temperature.

Bernoulli's Principle :

Because the flow is continuous, water speeds up when it flows through the narrow and/or shallow part of the brook.

Heat is energy in motion; it is energy in transit from a body of higher temperature to one of lower temperature. Once transferred, the energy ceases to be heat.

As an analogy, work is also energy in transit. A body does not contain work. It does work or has work done to it.

Between 0C and 4C, the volume of liquid water decreases as temperature increases. Above 4C, water behaves the way other substances do.

As water is cooled at the surface, it sinks until the temperature of the entire lake is 4C,. Only then can the surface water cool to 0C.

The force of the atmosphere a sea level against the outside of 10m^2 store window is about a million N. Why does this not shatter the window? Why might the window shatter in a strong wind blowing past the window? That is past the window not at the window...why?

Because the atmospheric pressure is the same on both sides Because the atmospheric pressure is lower outside in comparison to the pressure inside the store

Bermuda is about about as far north of the equator as north Carolina, but, unlike North Carolina, it has a subtropical climate year-round. Why is this so?

Bermuda is surrounded by water. Water tempers the climate. Therefore it will be take more energy to heat the water and similarly cool it down.

You're driving in a convertible car with the top up and the windows closed. You note that the fabric top puffs up. To explain this interesting phenomenon.

Bernoulli's principle. The top has more air flow so less pressure than the inside and it creates that puff

Why do you suppose that airplane windows are smaller than bus windows?

Bus windows have no significant pressure difference between the inside and the outside of the bus. This is not the case for airlines that fly 40,000ft in the air.

What is sublimation?

Change of the state of matter from solid to gas. It passes the state of liquid. Most notable in comets.

Why do electrically neutral atoms repel one another when they are close?

Everything is made out of atoms which are mainly empty space;

True of False? Temperature is a measure of the total kinetic energy in a substance.

False. it is of the average not total.

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

Fiberglass is made of several strands and it has air in between and air is a poor conductor of heat which is good for insulation purposes.

The atmosphere Air is mored compressed at sea level than at higher altitudes. Like feathers in a huge pile, what's at the bottom is more squashed than what's at the top.

Gravity applies more pressure lower so the buffer is denser on the troposphere (where we are located) than on the other spheres

Clouds are normally denser than air. So why don't clouds fall from the sky?

Hot air rises, as it rises it cools down, the moisture goes up, the air that remains and goes over the mountain is dry.

Why does the fire in a fireplace burn more briskly on a windy day?

If the wind is blowing on the top of the chimney it lowers the pressure which allows for more oxygen to come in and therefore creates a bigger fire.

Why arches?

If you have layers of stone on top of one another the force goes straight down, the weight pushes on the top and the arch redistributes the weight from the top of the sides.

The average mass of a giraffe's heart is around 40kg. Why is it so much heavier than your heart?

It has to be big because it has to pump blood higher to get to the giraffe's head; if you do not have blood supply getting to your brain then it can send you into a critical state, the heart has to be big enough to pump to every place of the body.

There is a I-beam. Why is it shaped this way?

It is as strong as a solid beam. The top part is stretched/under tension. The bottom is compressed. Therefore the middle portion is neutral. Can take material away without reducing the structural integrity. Less money for same result.

Why is it easier to float in salt water than fresh?

It is more dense and therefore you can float easier.

Why are airplanes pressurized?

It needs to be pressurized so that we can breathe and have are normal pressure that we are used to on ground.

Color of light you see out of the hole only depends on the interior temperature What is the color inside of a dark box

It's white. Radiation that inters the cavity (hole of the box) has little change of leaving because most of it is absorbed. For this reason, the opening to any cavity looks black to us.

Wrap a piece of paper around a thick metal bar and place it in a flame. Notice that the paper will not catch fire. Can you explain this in terms of the conductivity of the metal bar?

Metal is a good conductor so when you heat up the center the edges will be the same temperature, therefore you have to raise the temperature of the entire metal bar to burn it which would cost you much more energy.

If we warm a volume of air, it expands. Does it follow that, if we expand a volume of air it warms?

No; as expansion occurs it actually is cooling

Why do you suppose that girders are so often arranged to form triangles in the construction of bridges and other structures?

Rectangles are not great because it is easy to push away. It is better to use a triangle because you cannot push it anywhere.

On a boat ride, the skipper gives you a life preserver filled with lead pellets. When he sees the skeptical look on your face, he says that you'll experience a greater buoyant force if you fall overboard than your friends who wear Styrofoam-filled life preservers. Is he being truthful?

Styrofoam is less dense than you and therefore you will float. He is correct that your buoyant force is greater because you would be fully submerged and therefore displace more water.

The pressure at the bottom of a jug filled with water does NOT depend on : water density, the height of the liquid, none of the given variants, the acceleration due to gravity, and the surface area of the water

Surface area of the water: remember the formula for pressure: P=pgh (P= pressure p = rho (density) g = gravity and h= depth/height)

Heat is a measure of ENERGY not _________________

TEMPERATURE

When boarding an airplane, you bring a bag of chips and, while you are in flight, you notice that the bag puffs up. Explain why this happens.

The air pressure inside the airplane cabin is lower than the air pressure at sea level where the bag was packed. Therefore higher pressure inside the bag than outside => bag puffs up.

Why would you pick the silver pavement over the black tar to walk on?

The black will absorb more heat therefore it would be smarter to pick silver.

Why are dams shaped like this on the bottom )( .

The deeper the pond then the higher the pressure

When the temperature of the piece of metal is increased and the metal expands. Will the gap between the ends become narrower, or wider, nothing.

The gap will become wider when the metal expands. To see this pretend the shape is composed of little blocks, each the size of the gap. When heated each block will expand the same.

Why do some things heat up faster in a microwave than others?

The heat capacity of the object

When you touch a nail stuck in ice, does flow from the nail to your hand, or does energy flow from your hand to the nail?

The heat flows from conduction; a wooden nail is not a good conductor so it would not transfer the heat/cold where to the metal is a good conductor and therefore would transfer more of the heat/cold

Why is it that you can place your hand briefly inside hot pizza oven without harm, but you are burned if you touch the metal sides of the oven??

The heat flows from the oven to you but the air is a poor conductor so you do not burn. The second is that you make contact with relatively few molecules when you are putting your hand in. The corresponding low energy transfer borders on your threshold of feeling.

Which contributes more to an atom's mass — electrons or protons? Which contributes more to an atoms size?

The mass comes from the proton in the nucleus and the size comes from the electrons in the electron cloud

In desert regions that are hot in the daytime and cold at nighttime, the walls of houses are often made of mud. Why is it important that the mud walls be thick? How about the Adobe walls you can find in NM?

The mud has better insulation. The walls will hold in the heat from the day and let it out during the cool nights and then the cool that they gather at night will be slowly let out during the day.

Newtons law of cooling

The rate of loss of heat from an object is proportional to the temperature difference between the object and its surroundings.

Lower pressure means what to the size of air bubbles.?

The same concept as the bag. The air bubbles will get larger

The reason that they fly so high is?

There is less air resistance from the higher distance so its easier to fly. You also want to be above the clouds (which are made of water vapor)

Water molecules in ice link together to form an open structure. The open pockets in the structure are what makes ice less dense than water. Which is why ice floats on water. To be sure you interpret this correctly answer this: whats inside the open pickets? air, water vapor, or nothing?

There is nothing in between the ice crystals. They just form a crystalline structure that expand and there is nothing in the empty spaces. If there were air in the open spaces, they would have to show the molecules of air. Any water vapor would be seen as unassociated water molecules spaced relatively far apart. Neither of these are shown. instead, open pockets represent nothing but empty space.

How do igloos' work?

They insulate you from the outside. Your body will give off heat and it will keep it locked within the inside. Air is important because it is a poor conductor of heat but a good insulator.

You wish to bolt a sign to a horizontal I beam supporting a bridge. You will weaken the beam least if you drill the bolt holes through which layer?

Through the Neutral layer

Why is it easier for a chick inside an eggshell to poke its way out than it is for a chicken on the outside to poke its way in?

To poke its way into a shell, a chicken on the outside must contend with compression, which greatly resists shell breakage. But, when a chick pokes from the inside, only the weaker shell tension must be overcome.

When you step on a wooden floor, where the flooring is not directly supported, what part of the floor is under compression, and what part under tension?

Top is under compression and the bottom is under tension

What role does specific heat capacity play in a watermelon staying cool after removal from a cooler on a hot day?

Water has a high heat capacity so it takes a lot of energy to change the temperature. It is likely to stay cold for a long time.

Convection currents produced by unequal heating od land and water. During the day, warm air above the land rises, and cooler air over the water moves in to replace it. At night, the direction of air flow is reversed because then the water is warmer than the land.

We call this the sea effect; As the hot air rises it gets cooler and transformed into a liquid state aka cloud.

Why is Brownian motion apparent only for microscopic particles?

When looking at a microscopic level you can see the particles easier

Suppose that, at a restaurant, you are served coffee before you are ready to drink it. In order that it be hottest when you are ready for it, would you be wiser to add cream to it right away or when you are ready to drink it?

When the creamer is cool the temperature of the mixture to the coffee is cooler and therefore its going to be colder faster. Put the creamer in right away fro three reasons. Since black coffee radiates more heat than white coffee, make it whiter right away so it wont radiate and cool so quickly.

What happens when you have a main water break?

When the pressure is not as high there is contamination that occurs that can make you sick

A metal ball is just able to pass through a metal ring. When the ball is heated, however, it will not pass through the ring. What would happen if the ring, rather than the ball, were heated? Does

When the temperature increases the metal expands — in ALL directions. It gets thicker; its inner as well as its outer diameter increases; every part of it increases by the same proportion.

Why is it important to have a continuous high water pressure?

When there is high pressure it is difficult for things to contaminate the spring because of the amount of pressure

In a glass of water at room temperature, do all the molecules have the same speed?

Yes. The same average speed , but not the same instantaneous speed.

Archimedes Principle: An immersed body is buoyed up by a force equal to the weight of the fluid it displaces.

You can lift someone who is in water because the apparent weight is displaced and therefore the buoyant force acting up on the body is equal to the weight of the displaced liquid

When wet, the cloth covering on the sides of the canteen promotes cooling. Why?

You lower the temperature of the liquid on the inside of the bottle because the water on the outside will evaporate and take energy out of the system which will cool the water down. The fastest moving water molecules evaporate from the wet cloth.

Why do you sweat?

You sweat in order to regulate your body temperature. When you are getting hotter you sweat to let out of the heat. - Temperature is a measure of the average kinetic energy, when evaporation happens the fastest moving molecules can escape, when they escape the average kinetic energy gets lower and therefore the temperature gets cooler

Convection can be found in?

air, Convection current in liquid, Ocean currents, plate tectonics