chapter14 Flashcards
Atmospheric pressure decreases with increasing _________.
altitude
What is the mass of a cubic meter of air at room temperature (20°C)?
1.21 kg
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
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
Why would a water barometer have to be 13.6 times taller than a mercury barometer?
Mercury is 13.6 times denser than water
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
Why won’t a vacuum pump operate for a well that is deeper than 10.3 m?
Atmospheric pressure equals the pressure under 10.3 m of water and so can push water no higher
By how much does the density of air increase when it is compressed to half its volume?
It doubles.
What happens to the air pressure inside a balloon when it is squeezed to half its volume at constant temperature?
doubles
Does the air exert a buoyant force on all objects in air or only on objects such as balloons that are very light for their size?
Air exerts a buoyant force on all objects.
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
A helium-filled balloon will reach its maximum altitude when __________.
its weight equals the weight of displaced air
What happens to the internal pressure in a fluid flowing in a horizontal pipe when its speed increases?
The pressure decreases when the speed increases.
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
Is the fluid that goes up the inside tube in a hand sprayer pushed up the tube or sucked up the tube? Explain.
It is pushed up the tube by atmospheric pressure into the low-pressure, fast air stream.
The air in your classroom has
- mass
- weight
- energy
In drinking soda or water through a straw, we make use of
atmospheric pressure
At normal atmospheric pressure and temperature, 1 cubic meter of air has a mass of about
1.25 kg
When a suction cup sticks to a wall it is
pushed to the wall by the atmosphere
The weight of air in a column 1-m2 in cross section that extends from sea level to the top of the atmosphere is
101,000 N
A column that extends from sea level to the top of the atmosphere contains a certain mass of air. If the column instead contained the same mass of mercury, its height would be about
3/4 meter
Consider two mercury barometers, one with twice the cross-sectional area of the other. Neglecting capillarity, compared with the wider tube, mercury in the smaller tube will rise
to the same height
It would be easier to pull the evacuated Magdeburg hemispheres apart if they were
20 km above the ocean surface.
The weight of air in a bathtub (about 1/3 cubic meter) is about the same as the weight of
pound of butter
When a gas in a container is squeezed to half its volume with no change in temperature, the gas pressure
doubles
When boarding an airplane you bring a bag of chips. While in flight the bag puffs up, because
air pressure in the air-tight bag is greater than cabin air pressure
A bubble of air released from the bottom of a lake
becomes larger as it rises
The buoyant force of the atmosphere on a body is equal to the
weight of air displaced
Archimedes’ principle applies to
- fluid
- gas
- liquid
The buoyant force on a one-ton blimp hovering in air is
one ton
As a high-altitude balloon sinks lower into the atmosphere, it undergoes a decrease in
volume
A helium-filled balloon released in the atmosphere will rise until
the balloon and surrounding air have equal densities.
Compared with the buoyant force of the atmosphere on a 1-liter helium-filled balloon, the buoyant force of the atmosphere on a nearby 1-liter solid iron block is
same
Compared to the buoyant force of the atmosphere on a 1-kilogram iron block, the buoyant force on a nearby 1-kilogram helium-filled balloon is
considerably more
If you stand on a weighing scale and suddenly the atmosphere vanishes, taking buoyancy into account, the scale reading
increases
Airplane flight best illustrates
Bernoulli’s principle.
An umbrella tends to move upwards on a windy day principally because
air pressure is reduced over the curved top surface
When a gas in a container is squeezed to half its volume, its density
doubles
As a balloon rises higher and higher into the atmosphere its
none
As a high-altitude balloon rises higher into the atmosphere, it undergoes a decrease in
density
An object in a vacuum has no
buoyant force
A common 5-liter metal can will float in air if it is
no way, unless the displaced air weighs more than the can and its contents
An empty jar is pushed open-side downward into water so that trapped air cannot escape. As it is pushed deeper, the buoyant force on the jar
decreases
A spinning tossed baseball veers off course in the direction of
reduced air pressure on the ball.
When you blow air between a pair of closely-spaced Ping-Pong balls suspended by strings, the balls will swing
toward each other
As a balloon high in the atmosphere descends, it undergoes a decrease in
volume
A large block of wood and a smaller block of iron on weighing scales both register 1 ton. Taking buoyancy of air into account, which has the greater mass?
wood
How does the mass of the air in your bedroom compare to your mass?
they are approximately equal
