Pressure
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Question 1
a) A bottle has three tiny holes in the base of it. It is standing in a large bowl of water.
The bottle is filled with water.
When the bottle is removed from the bowl of water, the water in it flows out through
the small holes into the bowl. (fig.1)
If the cap is screwed on, the flow stops. (fig.2)
If the cap is unscrewed the flow begins again.
Fig.1
Fig.2
What prevents the water draining out of the bottle when the cap is replaced?
Why does the water flow out again when the cap is removed?
Do you think it would make a difference if the holes in the base were bigger?
Explain your answer:
b) A sucker cup will only work on perfectly smooth surfaces e.g. glass
Explain how the sucker cup sticks to the glass:
Why must the surface be perfectly smooth?
c) A student had a plastic syringe and a marshmallow.
Plunger
Nozzle
The marshmallow was placed in the syringe. (Fig.3)
A finger was placed over the nozzle of the syringe as shown and the plunger was pulled
outwards (Fig.4). The marshmallow expanded.
Fig.3
Fig.4
Explain why the marshmallow expanded and got bigger.
What happened to the pressure on the marshmallow?
What happened to the volume of the marshmallow?
d)
A page of stiff paper was folded in half to make a tunnel and placed on a table as shown
in the photograph.
A steady stream of air was blown through the tunnel (as shown by the blue arrow).
What do you think happened to the paper?
Explain your answer:
e) Pressure, Volume and Area are connected by the formula Pressure = Force / Area
Give 2 reasons, using the terms force, area and pressure, why the design of a drawing pin
is excellent for pushing into a notice board.
1.
2.
Explain, using the terms force, area and pressure, why the
girl can lie on the bed of nails without hurting herself.
Style A
Explain, using the terms force, area and pressure,
whether Style A or Style B shoes would be more
suited for walking on a sandy beach.
Style B
What is the pressure exerted on the floor by a
man standing on one leg?
Tick the correct box:
Half of the pressure he exerts when standing on two legs.
The same pressure as he exerts when standing on two legs.
Twice the pressure he exerts when standing on two legs.
Give a reason for your choice:
Question 2
a) The pictures below show what happens as water boils.
Boiling
At what temperature does water usually boil?
Where do the water molecules get the energy to escape from the beaker into the air?
From looking at the diagrams above, suggest how could you get water to boil at a
temperature above 100˚C?
To make good tea, the water has to be at 100˚C.
Climbers on top of Mount Everest boil a kettle of water
to make tea. They find that this boiling water is not hot
enough to make good tea. Suggest why this might be so?
b) Name an instrument used to measure the pressure of the air/atmosphere.
What unit is used when measuring the pressure of the air/atmosphere?
What are lines joining places of equal pressure on a weather map called?
Look carefully at the two weather charts.
What is a region of high pressure, H, called?
What do you think the weather conditions were in Ireland on June 8th, 2005?
What is a region of low pressure, L, on a weather chart called?
What does the “Today Monday” chart tell you about the weather in Ireland on that day?
The following are pressure measurements taken
by a climber climbing Mount Everest.
Height/km
1.3
5.3
5.3
6.6
7.0
7.4
7.8
8.2
8.6
Pressure/kPa
87
55
43
42
40
38
35
30
24
Show this data on a suitable graph or chart
From the graph, what do you think is the relationship between pressure and altitude?
Sometimes mountain climbers suffer from altitude sickness – dizziness and feeling faint.
Can you suggest one reason why this happens?
Reason:
Why do you think it is an advantage for athletes to train at high altitude?
Question 3
A student used a datalogger and a pressure sensor to investigate the relationship
between pressure and depth of a liquid.
A plastic funnel was attached to the pressure sensor. The sensor was connected to a
datalogger.
The funnel was lowered into the cylinder of water and pressure readings obtained at
different depths.
The graph below shows the data obtained for the pressure at different depths in the
water.
Depth (cm)
How did the student measure the depth of the liquid?
Using the graph, write down the atmospheric pressure on the day the experiment
was done.
Using the graph, explain what happens to the pressure as you go deeper in a liquid?
What is the pressure 4 cm down in the water?
A student used the same apparatus to investigate if the pressure is affected by the
density of the liquid.
She used three different liquids and their densities are shown in the table below,
Liquid
Density
Alcohol
0.84 g/cm 3
Water
1.00 g/cm 3
Seawater
1.15 g/cm
3
The graph shows the data she got for the three liquids.
Depth (cm)
Why did all three liquids have the same pressure at the surface?
From looking at the graph, do you think that the density of the liquid affects the pressure
in the liquid?
Give a reason for your answer:
Look at the table of densities.
Knowing that pressure depends on force and area, what do you think liquid A is?
Circle your answer
Alcohol
Saltwater
Explain your choice:
Deep sea divers wear a special suit called a Newtsuit
under water. One is shown in the photo.
The suit is made of very strong material and is filled
with air at a pressure of one atmosphere.
Give two reasons why divers wear Newtsuits when
examining sea wrecks on the ocean floor
1.
2.
The deepest parts of the oceans can only be
explored by using deep driving craft called
bathyscaphes. Explain why:
Suggest why divers have to take decompression breaks when rising from deep sea dives.
What happens to the volume of an air bubble
moving from the bottom of the sea to the surface?
Explain why you think this happens:
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