Physics III
A. an increase in pressure.
A blood platelets drifts along with the flow of blood through an artery that is partially blocked by deposits. As the platelet moves from the narrow region to the wider region, it experiences A. an increase in pressure. B. no change in pressure. C. a decrease in pressure. D zero pressure.
D. The pressure increasing because more air molecules are striking the walls of the tire.
A girl uses a pump to put air into her bicycle tire at constant temperature. A pressure gauge on the pump indicates the pressure inside the tire is increasing each time she pumps. What is the cause of this pressure increase? A. The air molecules repel each other more as more molecules are added and push outward. B. The volume of the tire is constant. C. The pressure increases to keep the temperature constant. D. The pressure increasing because more air molecules are striking the walls of the tire. E. The pressure increases because the air molecules are traveling faster.
B. It increases.
A hole is drilled in a metal plate. When the metal is raised to a higher temperature, what happens to the diameter of the hole? A. It decreases. B. It increases. C. It remains the same. D. The answer depends on the initial temperature of the metal.
D. difference between the weight of the stone and the weight of the displaced water.
A large aluminum cube in Figure 9.26 a) is resting on the bottom of the tank. The normal force of the bottom of the tank on the cube is equal to the A. weight of the stone. B. weight of the water displaced. C. sum of the weight of the stone and the weight of the displaced water. D. difference between the weight of the stone and the weight of the displaced water.
B. the water line is below the top surface of the Styrofoam.
A lead weight is fastened on top of a large solid piece of Styrofoam that floats in container of water. Because of the weight of the lead, the water line is flush with the top surface of the Styrofoam. If the piece of Styrofoam is turned upside down so that the weight is now suspended underneath it, A. the arrangement sinks. B. the water line is below the top surface of the Styrofoam. C. the water line is still flush with the top surface of the Styrofoam. D. do not have enough information to answer.
B. It will expand as the metallic portion expands.
A metallic key ring of 1.00 cm diameter is placed in a fire and heated up. What would you expect would happen to the inside diameter of the ring as it heats up? A. It will shrink as the metallic portion expands. B. It will expand as the metallic portion expands. C. It will stay the same size as the metallic portion expands. D. It is impossible to say what will happen to the open area in the center of the ring
D. 718
According to Figure 11.3 how many calories are required to change one gram of 0oC ice to 100oC steam? A. 118 B. 318 C. 518 D. 718 E. 918
B. convection.
Areas near a cold ocean or other cold body of water often experience a 'sea breeze' during the late morning, particularly on warm, sunny days. The process of energy transfer most directly associated with the development of the sea breeze is A. conduction. B. convection. C. radiation. D. none of the above
Perfect emitter/absorber, e = 1
Blackbody
A. the narrow part.
Blood flows through a coronary artery that is partially blocked by deposits along the artery wall. Through which part of the artery is the flow speed largest? A. the narrow part. B. the wide part. C. the flow speed is the same in both parts. D. do not have enough information.
C. C
By adding 25 kJ to solid material A, 4.0 kg will melt. By adding 50 kJ to solid material B, 6.0 kg will melt. Solid material C requires 30 kJ to melt 3.0 kg. Which of these materials, if any, has the largest value for the heat of fusion? A. A B. B C. C D. A=B
B. energy conservation in moving fluids.
Complete the following statement: Bernoulli's principle is a statement of A. momentum conservation in moving fluids. B. energy conservation in moving fluids. C. mechanical equilibrium in fluids. D. hydrostatic equilibrium.
C. that is equal to the weight of the fluid displaced by the object.
Complete the following statement: When an object is placed in a fluid, a buoyant force is exerted on it that is directed upward with a magnitude A. that is greater than the force of gravity on the object. B. that is greater than the weight of the fluid displaced by the object. C. that is equal to the weight of the fluid displaced by the object. D. that is less than the weight of the fluid displaced by the object. E. that is equal to the force of gravity on the object.
B. It will contract slightly (its volume will decrease).
Consider an amount of water freshly melted from snow in a pan and that the water has a temperature of 1°C. What will happen to the water as its temperature is increased to 3°C? A. It will expand slightly (its volume will increase). B. It will contract slightly (its volume will decrease). C. Its volume will not change. D. Its mass will decrease.
C. 1 g/cm3
Density of water at 0o C is: A. 1 kg/m3 B. 1 g/m3 C. 1 g/cm3 D. 1kg/cm3
While conduction is the transfer of heat energy by direct contact, convection is the movement of heat by actual motion of matter (due to different temperatures); radiation is the transfer of energy with the help of electromagnetic waves.
Differentiate between conduction, convection, and radiation
Internal energy, U, is the energy associated with the microscopic energy of the system Heat, Q, is the transfer of energy between a system and its environment because of a temperature difference between them
Differentiate between internal energy and heat
NO
Does pressure depend on shape of container?
Water flows faster in the narrow part and slower the wide part because A1V1 = A2V2. Area increases, so speed must decrease.
Does water flow faster in the narrow part of a river, or the wide part? Why?
B. 1/2.
Equal masses of hydrogen and helium gas are at the same temperature in vessels of equal volume. The atomic mass of helium is four times that of hydrogen. If the total mass of both gases is the same, the ratio of the pressure of helium (He) to that of hydrogen (H2) is A. 1/4. B. 1/2. C. 1. D. 2. E. 4.
Increasing number of molecules per unit volume in the container Increasing the average translational kinetic energy of the molecules
How can you increase pressure? (2 ways)
Radiation thermometer measures the intensity of the infrared radiation from the eardrum
How does a radiation thermometer work?
CONVECTION! The radiator warms the air in the lower region of the room. The warm air is less dense, so it rises to the ceiling. The denser, cooler air sinks. A continuous air current pattern is set up as shown.
How does a radiator work?
You apply a force to the balloon end, and increase the speed of the air. Since air speed increases, pressure is reduced. This creates a net force from the pressure below, inside the bottle, that prompts it to dispense fluid.
How does an old-fashioned perfume bottle work?
Through radiation
How does fire warm your hands?
C. radiation
How does the heat energy from the Sun reach us through the vacuum of space? A. conduction B. convection C. radiation D. none of the above.
All 3 - conduction, convection, and radiation!
How does the human body transfer heat?
B. increase pan bottom thickness
If cooking is done using an aluminum pan over an electric burner, which of the following will not promote the rate of heat flow from burner to food? A. increase pan bottom area B. increase pan bottom thickness C. increase burner temperature D. decrease height of pan sides
C. Quadruples.
If the speed of a molecule in a container doubles (other things remaining the same), the average pressure that this molecule exerts on the container wall A. Remains the same B. Doubles C. Quadruples. D. It is impossible to determine.
Decrease! Bernoulli's principle
If you have a fluid speeding up, what happens to the pressure?
B. the same as the force required to hold brick A in place.
Imagine holding two identical bricks under the water. Brick A is just beneath the surface of the water, while brick B is at greater depth. The force needed to hold brick B in place is A. larger than the force required to hold brick A in place. B. the same as the force required to hold brick A in place. C. smaller than the force required to hold brick A in place. D. can not be deduced from information given.
Vrms = 1/(M)^1/2, so the lighter particle must move faster at a given temperature. VH2/VO2 = (MO2/MH2)^1/2 = (32/2)^1/2 = 4
In a gas with H and O molecules in thermal equilibrium, which ones move faster, and by which factor?
True
In ideal gas the molecules interact only during the elastic collisions but otherwise do not exert any forces on each other. True False
C. be in thermal equilibrium.
In order for two objects to have the same temperature, they must A. be in thermal contact with each other. B. have the same relative "hotness" or "coldness" when touched. C. be in thermal equilibrium. D. have all of the properties listed above. E. have only properties (b) and (c) above.
A. when the person is lying down on the floor
In which of the following cases would the maximum "contact pressure" from the floor on a person be the least? A. when the person is lying down on the floor B. when the person is sitting on the floor C. when the person is standing on the floor D. when the person is standing on their tip-toes on the floor
C. It's because the thermal conductivity of carpet is less than that of tile.
Inside a house, stepping on a tile floor barefooted may feel almost cold, but stepping on carpet in an adjacent room feels comfortably warm. Why is this? A. It's because the tile is below room temperature while the carpet is at room temperature. B. It's because the tile is at room temperature while carpet is normally warmer. C. It's because the thermal conductivity of carpet is less than that of tile. D. It's because the thermal conductivity of tile is less than that of carpet.
D. Yes, in some cases a substance's temperature will change when energy is added to the substance. In other cases, the substance's temperature will not change when energy is added.
Is it possible to add energy to an isolated substance and not have the substance's temperature change? A. No, the subtsance's temperature will always go up when energy is added to it. B. No, the substance's temperature will sometimes go up and sometimes go down when energy is added, but it will always change. C. Yes, temperature change is not a function of energy added to a substance. D. Yes, in some cases a substance's temperature will change when energy is added to the substance. In other cases, the substance's temperature will not change when energy is added.
melting or freezing
Latent heat of fusion
Boiling or condensing
Latent heat of vaporization
A. The internal energy decreases.
Let's say that an ideal gas decreases in temperature, but that its volume remains constant during this process. What happens to its internal energy in this case? A. The internal energy decreases. B. The internal energy increases. C. The internal energy remains constant. D. It cannot be determined whether it will increase, decrease, or remain the same.
Objects are in thermal contact if energy can be exchanged between them
Objects are in thermal contact if...
Area under the curve
On a Stefan-Boltzmann plot of intensity vs wavelength, how do we determine total radiation emitted?
D. specific heat
On a sunny day at the beach, the reason the sand gets so hot and the water stays relatively cool is attributed to the difference in which property between water and sand? A. mass density B. temperature. C. thermal conductivity D. specific heat
Light particles are moving faster, so overall KE is the same (mass decreases, but v increases, and T is kept constant). P = 2/3(N/V)(1/2 * mv^2) Pressure is directly proportional to the average KE and # of moles
Pressure is the same, for same amount of particles, in a closed container, regardless of if particles are heavy or light. Why?
Shortest = ultraviolet Longest = infrared
Shortest/longest wavelengths?
True! Specific heat of liquid water is highest, followed by steam, followed by ice
T/F: The same substance in different phases can have different specific heats Use water as an example to justify your claim
True!
T/F: every object, including the human body, can radiate + absorb radiation. That process will continue until the object reaches thermal equilibrium with its environment
C. change in momentum of a gas molecule due to collision with wall
The force on the walls of a vessel of a contained gas is due to: A. repulsive force between gas molecules B. slight loss in average speed of a gas molecule after collision with wall C. change in momentum of a gas molecule due to collision with wall D. elastic collisions between gas molecules E. inelastic collisions between gas molecules
B. The loss doubles.
The inside of a house is at 20 °C on an early morning when the temperature outside is 15 °C. The next morning the inside temperature is the same but the outside temperature is now 10 °C. How much does the energy per unit time lost by conduction through the walls, windows, doors, etc., change for the house from the first morning to the second one? A. Since the inside temperature stays the same, the loss is the same both days. B. The loss doubles. C. The loss halves. D. The loss increases by 5/288 since we need to use the Kelvin scale for this calculation.
The weight of the displaced water
The magnitude of the buoyance force equals what?
C. greater than P.
The pressure at the bottom of a glass of fresh water is P. The water is poured out and is replaced with seawater. The new pressure at the bottom of the glass is A. smaller than P. B. equal to P. C. greater than P. D. indeterminate.
B. lower than in the non-constricted region.
The pressure in the constricted region of artery shown in Figure 9.36 is A. higher than in the non-constricted region. B. lower than in the non-constricted region. C. same as in the non-constricted region. D. can not be determined from the information given.
C. The two weigh the same.
Two cups are filled to the same level with water. One of the two cups has plastic balls floating in it. If the density of the plastic balls is less than that of ice, which of the two cups weighs more? A. The cup without plastic balls. B. The cup with plastic balls. C. The two weigh the same.
D. in neither, the flow rate is the same in both pipes
Two pipes are smoothly connected together without leaks. One has a diameter of 3 cm and the other has a diameter of 5 cm. Water flows through the pipes. In which pipe is the volume flow rate the greatest? A. in the pipe that the water flows through first (the "upstream" pipe) B. in the 3-cm pipe C. in the 5-cm pipe D. in neither, the flow rate is the same in both pipes
A. Star A.
Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with RA = 0.5 RB, and TA = 2 TB. Assuming the temperature of space to be negligible, which star radiates the most energy per unit time? A. Star A. B. Star B. C. Both radiate the same amount of energy per unit time. D. More information is needed in order to make a determination.
Two objects in thermal equilibrium with each other are at the same temperature
Under what conditions can we say that two objects are in thermal equilibrium with each other?
The volume of fluid that enters one end of the tube in a given time interval equals the volume of fluid leaving the tube in the same interval
Voiceover: Equation of continuity
1. In general, liquids become more dense as they cool, because mass stays the same while volume decreases (P=m/v). This isn't true for water, though! At 4C, water starts to expand, and therefore becomes less dense 2. Water has the highest specific heat of any liquid
What do we mean when we say 'unusual behavior of water'?
Tells us how much energy is being emitted or absorbed by the object at a certain temperature
What does intensity on a Stefan-Boltzmann plot tell us?
Characteristics of the substance, including: thermal conductivity, k width of object, delta x Difference in temperatures (in Kelvin, T-T)
What does rate of conduction depend upon?
Relates pressure to fluid speed and elevation. Can be used like conservation of ME. Applies to ideal fluids. P + 1/2pv^2 + pgy = constant
What is Bernoulli's equation and why do we care?
he root-mean-square speed is the measure of the speed of particles in a gas, defined as the square root of the average velocity-squared of the molecules in a gas.
What is RMS speed?
All gases extrapolate to the same temperature at zero pressure. This temperature is absolute zero, given by 0K (-273 C).
What is absolute zero?
Heat is energy exchanged between objects (note - heat itself is not energy. heat is exchange of energy)
What is heat?
During a phase change, amount of heat is given by: Q = +- m*L, where L is the latent heat Choose positive sign if adding, negative sign if subtracting
What is latent heat? Why do we care?
The physical cause of the buoyant force is the pressure difference between the top and the bottom of the object (pressure is different because they're at different levels y)
What is the cause of the buoyant force?
PV = nRT where n can be equal to m/M, but m MUST be in kg (so adjust accordingly) p is in Pa V is in m^3 R = 8.31 J/mol*K T is in Kelvin
What is the ideal gas law (physics version) including units?
0C
What is the temperature if water and ice are both present?
100C
What is the temperature if water and steam are both present?
At or around 4C, because this is the last temperature that the water would sink at (otherwise, it expands, and is less dense)
What is the temperature of water near the bottom of a lake?
The point at which water exists in all 3 phases. 273.16K, 0.01C
What is the triple point of water?
In order for a phase change to occur, energy must be added or taken away. This is because bonds must be loosened or formed. Important - no temperature change!
What needs to happen for a phase to change? Why?
Average KE is given entirely by T KEaverage = N3/2KbT = 3/2nRT
What's the relationship between KE and T?
Thermal equilibrium exists when two objects in thermal contact with each other cease to exchange energy
When does thermal equilibrium exist?
D. an increase in the pressure at constant volume
Which of the following could be associated with a temperature increase for a fixed amount of gas? A. a decrease in the volume at constant pressure B. a decrease in the pressure at constant volume C. a decrease in both the pressure and the volume D. an increase in the pressure at constant volume
A. One gram of steam at 100°C changing to water at 100°C.
Which of the following involves the greatest heat transfer? A. One gram of steam at 100°C changing to water at 100°C. B. One gram of ice at 0°C changing to water at 0°C. C. One gram of water cooling from 100°C to 0°C. D. One gram of ice heating from -100°C to 0°C.
B. 0.100 kg of water at 22 oC
Which of the following substances would be the most effective in cooling 0.300 kg of water at 98 °C? A. 0.100 kg of lead at 22 oC B. 0.100 kg of water at 22 oC C. 0.100 kg of glass at 22 oC D. 0.100 kg of iron at 22 oC
B. The buoyant force depends on the volume of the liquid displaced.
Which one of the following statements concerning the buoyant force on an object submerged in a liquid is true? A. The buoyant force will increase with depth if the liquid is incompressible. B. The buoyant force depends on the volume of the liquid displaced. C. The buoyant force depends on the weight of the object. D. The buoyant force depends on the mass of the object. E. The buoyant force is independent of the density of the liquid.
B. The specific heat is the amount of energy per unit mass to raise the temperature of the object by 1 oC.
Which one of the following statements is the definition of the specific heat of an object? A. The specific heat is the amount of energy per unit mass to raise the temperature of the object from its freezing point to its boiling point. B. The specific heat is the amount of energy per unit mass to raise the temperature of the object by 1 oC. C. The specific heat is the temperature of the object divided by its density. D. Given one gram of the material, the specific heat is the amount of energy to change the material from solid to liquid. E. Given one gram of the material, the specific heat is the amount of energy to change the material from a solid to a gas.
Area decreases, so speed increases (A1V1 = A2V2). Speed increase causes pressure to decrease. The change in pressure is not good for the heart
Why are deposits in the aorta bad? Explain using Bernoulli's principle.
40% from melting glaciers, 60% from expansion as ocean temperatures rise
Why are sea levels rising?
Airplane wings aren't flat in order to ensure that the air speed above the wing is greater than the speed below. This makes it so that the air pressure above the wing is less than the air pressure below, which provides a 'lift' force to keep the airplane up. (Net force in the upward direction) In order for a plane to be in level flight, lift on both wings has to support the weight of the plane, so the larger the plane, the larger the area of the wings
Why aren't airplane wings flat? How do we ensure level flight? What is the lift force?
Pressure = Force/Area Force = Area*pressure So to make the net upward force as large as possible, you want the greatest area of the wings
Why do giant planes have giant wings?
Because of the unusual behavior of water! Water at and below 4C starts to exand, so it rises to the top before it freezes. At 0, when it begins to freeze it stays on top, and ice begins to form
Why do lakes freeze from the top down?
If a car is going REALLY fast, the speed of the air above is way faster than the speed of the air below. That means that pressure below >> pressure above, so the car is in danger of flipping. Spoilers prevent the car from flipping by slowing the speed of the air above the car without having too much drag (reduce the speed above to push the car down)
Why do some cars have spoilers?
2 reasons: 1. Need to reduce speed as landing 2. Reducing speed also reduces the lift! So trying to increase the area to keep up lift while slowing down
Why do the flaps come up when an airplane is trying to land?
Convection! The sun delivers the same amount of heat per unit mass to both sand and water. But! The specific heat of sand << specific heat of water. Sand transfers heat to air above sand, either by radiation or conduction. Water transfers heat to air above water, either by radiation or conduction. The air above the water, though, won't be as hot as the air above the sand, because of the specific heat differential, so convection begins. Colder air moves towards the shore to replace hot air... feels like a breeze coming off of the water.
Why do you feel a breeze on a hot day at the beach?
Air is moving inside of the shower, so speed increase causes pressure to decrease. This causes net force from outside pushing in, which pushes the curtain towards you
Why does a shower curtain pull in when you shower?
Water is in free fall, so speeding up. If v is increasing, cross-sectional area, and therefore width, must decrease (volume per unit time can't change!) This is equation of continuity
Why does a stream of water narrow as it falls from the faucet?
Metal is actually in thermal eq. with the rest of the room (at the same temperature), as is the book, so they're likely the same temperature. Heat is transferred from your hand to the objects when you touch them. Therefore, the sensation of "coldness" is related to how fast heat is leaving your hand. Metal feels colder because energy is larger - energy is faster to leave your hand. Rate of transfer of conduction depends on the characteristics of the substance.
Why does metal feel colder to the touch than a book?
By blowing above, we create a 'lift' force. Can be explained by Bernoulli's principle: P + 1/2pv^2 + pgy = constant Because speed of air above increases, pressure above must decrease. This means that there is a net force from the pressure below pushing up!
Why does paper flip up if you blow above it?
Because it's thermal conductivity value is relatively low (see: table, it's about 0.2 vs. 238 for aluminum, e.g.)
Why does rubber make a good insulator?
Rate at which heat enters the room depends on the thickness of the walls (so heat will enter the room slowly)
Why is it nice to be in a basement with thick walls on a hot day?
Because of the unusual behavior of water! Water at and below 4C starts to exand, so it rises to the top before it freezes. Water that isn't yet frozen sinks to the bottom, and allows marine life to live.
Why is it possible for fish to live at the bottom of a lake?
Due to high specific heat of water and convection! Water of the pacific ocean releases huge amount of heat into the air above the water. Why is this different than the east coast? Well, the same heat release is happening, but west is milder because the prevailing winds push air towards the land, while on the east coast, they push air away from the land
Why is the west-coast climate more mild during the winter?
Because of static equilibrium! If pressure wasn't the same, there would be a net force, and the fluid would be in motion
Why must all points at the same depth be at the same pressure?
If you sum the thermal resistance of those layers, including the air between, you will end up with a larger R value, and therefore smaller total heat transfer (heat leaves your body slower, cold enters your body slower)
Why should you layer on a cold day?
A. the liquid water
You have 1 kg of liquid water and 1 kg of steam. If you want to increase the temperature of both of them by 10 oC, which would require more added energy? A. the liquid water B. the steam C. They both require the same amount of energy to be warmed 10 oC. D. It cannot be determined because it depends on the actual temperature of the water and steam as well as the pressure.
The difference in the tension forces is the buoyant force
You have an object suspended by a string in air. Then, that same object is put into water. How do you calculate the difference in the tension forces?
Perfect reflector, lighter the object smaller the e
e = 0