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Physics Test 3
Terms in this set (140)
In a vaccuum a marshmallow becomes ___.
What is the term for a direct change of state from a solid to a gas?
A metal block has a density of 5000 kg per cubic meter and a volume of 2 cubic meters. What is the block's mass?
What is the term for a change of state from a solid to liquid?
Consider a break that is totally immersed in water, with the long edge of the brick vertical. The pressure on the brick is...
greatest on the bottom of the brick.
If a loaf of bread is compressed, its...
The pressure differential across a wing cross section due to the difference in air flow is explained by ____.
The hydraulic lift is an application of ____.
When you touch a piece of ice, ....
thermal energy flows from your hand to the ice.
Which of the following is NOT a unit of pressure?
The heat required to change a substance from the liquid to the vapor state is referred to as the ____.
When gas in a container is squeezed to half its volume, its density...
A 10kg piece of aluminum sits at the bottom of a lake, right next to a 10kg piece of lead, which is much denser than aluminum. Which one has the greater buoyant force on it?
The aluminum one.
The faster a fluid moves, the...
less its internal pressure.
The type of heat transfer that occurs between a stove and a pot place on it is ____.
A balloon is buoyed up with a force equal to the...
weight of air it displaces.
An umbrella tends to move upwards on a windy day principally because...
air pressure is reduced over the curved top surface.
The type of heat transfer that occurs between a heating lamp and the food that it's keeping warm is ___.
To melt ice, add ____.
Steam burns can be much more severe than burns caused by burning water. The reason for this is that...
steam delivers more energy to the skin than boiling water does.
When an object is partly or wholly immersed in a liquid, it is buoyed up by...
a force equal to the weight of liquid displaced.
It is a well-known fact that water has a higher specific heat than iron. Now, consider equal masses of water and iron that are initially in thermal equilibrium. The same amount of heat, 30 Joules, is added to each one. Which statement is true?
They are no longer in thermal equilibrium; the iron is warmer.
proportional to force and inversely proportional to area.
If the mass of an object were due to double while its volume remains the same, its density would ___.
Salt water is more dense than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of water displaced in the salt water is ___.
The reason that buoyant force acts upward on a submerged object is that...
upward pressure against the bottom is greater than downward pressure against the top of the submerged object.
proportional to mass and inversely proportional to volume.
The ratio of output force to input force of a hydraulic press will be equal to the ratio of the output and input piston ____.
As a high-altitude balloon sinks lower and lower into the atmosphere, it undergoes a decrease in ___.
The temperature at which water freezes is the same as the temperature at which...
"An external pressure applied to an enclosed fluid is transmitted unchanged to every point within the fluid" is known as ____ principle.
If you wanted to know how much the temperature of a particular piece of material would rise when a known amount of heat was added to it, which of the following would be most helpful to know?
A block of styrofoam floats on water while a same size block of lead lies submerged in the water. The buoyant force is greatest on the ___.
Phase changes occur...
as the temperature remains the same.
When a liquid freezes...
heat energy leaves the substance.
If the temperature of an iron sphere is increased...
its density will decrease.
A dam is thicker at the bottom than at the top partly because...
water pressure is greater with increasing depth.
One day, while swimming below the surface of the ocean, you let out a number of bubbles of air from your mouth. As the bubbles rise towards the surface, their diameters will ___.
When water freezes, it expands. What does this say about the density of ice compared to the density of water?
Ice is less dense than water because it has more volume for the same mass.
At what temperature does all the water in a lake need to reach before it will freeze on top? ___ degrees Celsius.
An immersed object is buoyed up by a force equal to the weight of the fluid it displaces.
A force divided by the area over which the force is exerted. (Pressure= force/area)
Liquid Pressure is equal to what?
Weight x depth
The net upward force exerted by a fluid on a submerged or immersed object.
Principle of flotation
A floating object displaces a weight of fluid equal to its own weight.
Changes in pressure at any point in an enclosed fluid at rest are transmitted undiminished to all points in the fluid and act in all directions.
Pressure exerted against bodies immersed in the atmosphere resulting from the weight of air pressing down from above. At sea level, atmospheric pressure is about 101kPa.
A device used to measure the pressure of the atmosphere.
The product of pressure and volume is a constant for a given mass of confined gas regardless of changes in either pressure or volume individually, as long as the temperature remains unchanged.
The pressure in a fluid along a given streamline decreases as the speed of the fluid increases.
The fourth phase of matter, in addition to solid, liquid, and gas. In the plasma phase, which exists mainly at high temperatures, matter consists of positively charged ions and free electrons.
The pressure increases on a block resting on a table when you increase the ___.
downward force on the block.
How does pressure relate to force?
Pressure is force per unit area.
Water pressure in a lake is greater ___.
at the bottom.
How does pressure at the bottom of a body of water relate to the weight of water above each square meter of the bottom surface?
The pressure is the weight of the water divided by 1 m^2.
What is the relationship between liquid pressure and the depth of a liquid? Between liquid pressure and weight density?
Pressure is proportional to both depth and weight density.
If you swim beneath the surface in saltwater, will the pressure be greater than in fresh water at the same depth?
The pressure will be greater.
How does the water pressure 1 m below the surface of a small pond compare with the water pressure 1 m below the surface of a huge lake?
The pressure will be the same.
If you punch holes in the side of a container filled with water, in what direction does the water initially flow outward from the container?
It flows straight out, perpendicular to the wall.
A stone submerged in water displaces the _____.
volume of water.
Why does the buoyant force act upward on an object submerged in water?
The pressure upward on the deeper bottom is greater than the downward pressure on the top.
Why isn't there a horizontal buoyant force on a submerged object?
Force vectors on the sides cancel one another.
How does the volume of a completely submerged object compare with the volume of water displaced?
The volumes are equal.
If an object suspended by a scale shows a weight of 3 N in air, and 2 N when submerged in water, the buoyant force
How does the buoyant force on a submerged object compare with the weight of the water displaced?
The buoyant force is equal to the weight of the water displaced.
Distinguish between an immersed and a submerged body.
A submerged body is completely surrounded by fluid, whereas an immersed one is partially or completely surrounded.
What is the mass of a 1 L of water? What is its weight in newtons?
1 kg; 10 N
If a 1-L container is immersed halfway into water, what is the volume of the water displaced? What is the buoyant force on the container?
0.5 displaced, 5 N buoyant force.
An object having the same density as water will ____.
Neither sink nor float in water.
Is the buoyant force on a submerged object equal to the weight of the object itself or is it equal to the weight of the fluid displaced by the object?
It is equal to the weight of the fluid displaced.
What is the condition in which the buoyant force on an object does equal the weight of the object?
The object is neutrally buoyant, so it will neither sink nor float.
Does the buoyant force on a submerged object depend on the volume of the object or on the weight of the object?
What will these objects do in water: an object denser than water, an object less dense than water, an object that has the same density as water.
Sink, float, neither sink nor float.
How is the density of a fish controlled? How is the density of a submarine controlled?
A fish changed its volume, whereas a submarine changes its weight.
How much air must a 100-ton blimp displace to float and neither rise nor sink?
The operation of a hydraulic press best illustrates ____.
conservation of energy.
What happens to the pressure in all parts of a confined fluid f the pressure in one part is increased?
The pressure everywhere increases by the same amount.
If the pressure in a hydraulic press is increased by an additional 10 N/cm^2, how much extra load will the output piston support if its cross-sectional area is 50cm^2?
Atmospheric pressure decreases with increasing ____.
What is the energy source for the motion of gas in the atmosphere? What prevents atmospheric gases from flying off into space?
Solar energy, gravity.
How high would you have to go in the atmosphere for half of the mass of air to be below you?
What is the cause of atmospheric pressure?
The weight of the air
What is the approximate mass of a column of air 1 cm2 in area that extends from sea level to the upper atmosphere? What is the weight of this amount of air? What is the pressure at the bottom
1 kg, 10 N, 100 kPa
How does the pressure at the bottom of a 76-cm column of mercury in a barometer compare with the air pressure at the bottom of the atmosphere?
The pressures are equal.
Why would a water barometer have to be 13.6 times taller than a mercury barometer?
Mercury is 13.6 times denser than water.
How does the weight of mercury in a barometer compare with the weight of an equal cross-section of air from sea level to the top of the atmosphere?
They are equal.
When you drink liquid through a straw, is it more accurate to say the liquid is pushed up the straw rather than sucked up the straw? What exactly does the pushing?
The atmospheric pressure outside the straw pushes the liquid toward the lower pressure in your mouth.
By how much does the density of air increase when it is compressed to half its volume?
What happens to the air pressure inside a balloon when it is squeezed to half its volume at constant temperature?
When a party balloon is compressed to one-third its volume, gas pressure in the balloon ___________.
A balloon that weighs 1 N is suspended in air, drifting neither up nor down. (a) How much buoyant force acts on it? (b) What happens if the buoyant force decreases? (c) If the buoyant force increases?
(a) 1 N up; (b) it falls; (c) it rises.
Why are high-altitude research balloons only partially inflated when launched?
The atmospheric pressure decreases as they rise, so they expand. If they were fully inflated at launch, they would burst at high altitudes.
How does faster-moving air above an airplane wing affect the pressure on the wing?
The speed increases as the air flows over the wing, so the pressure decreases.
Does Bernoulli's principle refer to changes in the internal pressure of a fluid or to pressures the fluid may exert on objects?
Internal pressure only
What happens to the internal pressure in a fluid flowing in a horizontal pipe when its speed decreases?
The pressure increases when the speed decreases.
When the speed of a fluid increases, internal pressure in the fluid __________.
Air pressure over the surface of a bird's wings decreases when __________.
air speed increases there
A gas will become plasma when it is __________.
Cite at least three examples of plasmas in your daily environment.
Fluorescent lights, neon lights, plasma televisions
Which one of these cites the lowest temperature?
The temperature of absolute zero is stated as ___________.
What are the temperatures for freezing water on the Celsius and Fahrenheit scales? For boiling water?
Freezing: 0°C, 32°F; boiling: 100°C, 212°F
What are the temperatures for freezing water and boiling water on the Kelvin temperature scale?
273 K, 373 K
What is meant by "translational" kinetic energy?
Kinetic energy of motion that carries a molecule from one place to another.
Which forms of energy determine temperature: translational kinetic energy, rotational kinetic energy, vibrational kinetic energy, or all of these?
What is meant when we say that a thermometer is in thermal equilibrium with another object?
Heat no longer flows between the object and thermometer when both are at the same temperature.
When we speak about heat we refer to ___________.
energy in transit
Which one of these is largest amount of energy?
The amount of heat needed to raise the temperature of water by 1°C is ___________.
In which direction does heat flow spontaneously between hot and cold objects?
From high temperature to low temperature
What role does temperature have in the direction of heat flow?
Heat flows spontaneously from high temperature to low temperature.
How many joules (J) are needed to change the temperature of 1 gram of water by 1°C?
Which of these has the highest specific heat capacity?
Hot sand cools off faster at night than plants and vegetation. This indicates that the specific heat capacity for sand is ___________.
less than that of plants
Which warms up fastest when heat is applied: water, iron, or silver?
Silver warms up faster than iron. Iron warms up faster than water.
Does a substance that heats up quickly have a high or a low specific heat capacity?
A low specific heat capacity
Does a substance that cools off quickly have a high or a low specific heat capacity?
A low specific heat capacity
Water is most dense at ___________.
How does the specific heat capacity of water compare with the specific heat capacities of other common materials?
Water has a higher specific heat capacity than most common materials.
Why do substances expand when their temperature is increased?
Higher-temperature substances have greater molecular motion.
Why does a bimetallic strip bend with changes in temperature?
The two metals expand at different rates.
When the temperature of ice-cold water is increased slightly, does it undergo a net expansion or a net contraction?
Why does all the water in a lake have to be cooled to 4°C before the surface water can be cooled below 4°C?
When water is cooled to 4°C, it sinks and deeper, warmer, water rises to the surface.
When your foot stands on a tile floor, thermal energy always flows _________.
from either your foot or the tile, depending on the temperature of the tile
If you touch the metal sides in an oven with your bare hand, you're in trouble. But hold your hand briefly in the oven air and you're okay. What does this tell you about the relative conductivities of metal and air?
Metal is a good conductor of heat, whereas air is a terrible conductor of heat.
Explain why a firewalker can step quickly without harm on red-hot coals with bare feet.
Wood, even as glowing coals, is a poor conductor of heat.
Why are materials such as wood, fur, feathers, and even snow good insulators?
Outer electrons in these materials are firmly attached.
Does a good insulator prevent heat from escaping or slow its passage?
Insulators slow the passage of heat.
Thermal convection applies mainly to _________.
What happens to the volume of air as it rises? What happens to its temperature?
Volume increases; temperature decreases.
Heat travels from the Sun to Earth by the process of _________.
How are the speeds of molecules of air affected as they separate from one another when escaping from the nozzle of a party balloon? What happens to the temperature of the air?
Speeds decrease; temperature decreases.
When an air molecule is hit by an approaching, faster moving molecule, does the approaching molecule's rebound speed increase or decrease? How about when it hits a receding molecule?
The relation f ~ T tells us that high temperature sources emit electromagnetic waves of _________.
In what form does radiant energy travel?
As electromagnetic waves
Relatively speaking, do high-frequency waves have long wavelengths or short wavelengths? Name an electromagnetic wave with higher frequency than blue light.
Which will normally warm faster: a black pot of cold water or a silvered pot of cold water? Which will cool faster?
Can an object be both a good absorber and a good reflector at the same time?
No. A good absorber reflects very little light.
How does glass act like a one-way valve for a conventional greenhouse? Does the atmosphere similarly act as a one-way valve?
Glass transmits solar radiation into the greenhouse and blocks infrared radiation from leaving the greenhouse. The same thing happens in the atmosphere.
Cite three ways in which a Thermos bottle inhibits heat transfer.
There is no conduction and no convection through a vacuum, and silvered surfaces stops radiation.
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