PHY2216: Tutorial Questions 2
PRESSURE IN FLUIDS
Where necessary, and unless otherwise stated, use the following data:
Atmospheric pressure = 1.01 x 104Pa (or 760mmHg),
Density of mercury = 1.36 x 104kgm-3,
Acceleration due to gravity, g = 9.81 m s-2
1.
Use the following figure to calculate the pressure of the gas in the bulb.
[Answer: 1.17 x 105Pa]
2.
An open U-tube manometer containing an oil of density 897 kgm-3 is used to measure the
pressure of a gas. The oil level in the open tube is 25.0 cm higher than that in the limb
connected to the gas. Calculate the:
(i)
gauge pressure,
(ii)
absolute pressure of the gas. (Atmospheric pressure = 9.98 x 104 Pa)
[Answer: (i) 2.2 x 103 Pa (ii) 1.02 x 105 pa]
3.
The pressure on the upper surface of a submerged US Naval submarine is 1.20 x 106 Pa;
the pressure on the base of the hull is 1.40 x 106 Pa. Calculate the height of the
submarine. (Density of seawater = 1.04 x 103 kg m-3.)
[Answer: 19.6 m]
4.
Use the following figure to calculate the pressure of the gas in the bulb.
[Answer: 730 mmHg]
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5.
Find the pressure of the enclosed gas in each of the following situations;
[Answer: (a) 30 mmHg (b) 800 mmHg (c) 1.962 x 103Pa]
6.
A beaker of cross-sectional area 60 cm2 contains 600 cm3 of mercury. Find the pressure
on the inner surface of the base of the beaker
[Answer: 860mmHg or 1.14 x 105Pa]
7.
An open U-tube manometer containing mercury records the pressure of a gas as 150kPa
when the atmospheric pressure is 100kPa. If the mercury level in the open tube is h mm
higher than that in the limb which is in contact with the gas, what is the height difference,
h, of the mercury surfaces?
[Answer: 0.375m]
8.
An open U-tube manometer containing mercury is used to measure the pressure of a gas.
The mercury level in the open tube is 600mm higher than that in the limb which is in
contact with the gas. What is the pressure (in pascals) of the gas?
[Answer: 1.81 x 105Pa]
9.
The diagram shows a mercury manometer recording a pressure of 150kPa. If the
atmospheric pressure is 100kPa, what is the height difference h of the mercury surface?
[Answer: 36.8cm]
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10.
An object is weighed with a spring balance, first in air and then whilst totally immersed
in water. The readings on the balance are 0.48N and 0.36N respectively. Calculate the
density of the object. (Density of water = 1.0 x 103kgm). [Answer: 4.0 x 103kgm–3]
11.
A boy tries to use a garden hose to supply air for a swim at the bottom of a 50m deep
pool. What goes wrong?
[Answer: His lings, and the hose through which he is breathing, may collapse]
12.
A hydraulic press consists of two cylinders of cross-section 0.2m2 and 5.0m2. If the
position in the smaller cylinder is pushed down with a force of 100 N through a distance
of 0.2 m, calculate:
(i)
the pressure transmitted by the fluid,
(ii)
the force exerted by the piston of the large cylinder.
[Answer: (i) 500Nm–2 (ii) 2500N]
13.
A car weighing 1.2 x 104N rests on four tires.
(a)
If the gauge pressure in each tire is 200kPa, what is the area of each tire in contact
with the road?
(b)
If the car sits on a hydraulic press, and the area of the cylinder holding the car up
is 4 times greater than the area of the cylinder on the other side of the press, what
is the force that must be applied to the other side of the hydraulic press?
[Answer: (a) 0.015m2 (b) 0.3 x 104N]
14.
A body has a weight of 160N when weighed in air and a weight of 120N when totally
immersed in a liquid of relative density 0.8. What is the relative density of the body?
[Answer: 3.2]
15.
The areas of the effort and load pistons of a hydraulic press are 0.5m2 and 5m2
respectively. If a force, F1, of 100N is applied on the effort piston, determine the force,
F2, on the load.
[Answer: 1000N]
16.
An object weighs 10N in air and 7N in water. What is the weight when immersed in a
liquid of relative density 1.5?
[Answer: 5.5N]
17.
What is Matter?
18.
(a)
(b)
19.
Explain what is meant by center of buoyancy. For maximum stability, how should the
center of gravity relate to the metacenter?
20.
What happens if a body cannot displace its own weight of fluid, even when completely
immersed?
State the Archimedes’ Principle.
The principle of flotation applies to both partially and totally immersed bodies.
Give an example, each of partially immersed and totally immersed bodies.
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