Ch 4
MCQ
1 1- All fluids are:
A. gases
C. gases or liquids
B. liquids
D. non-metallic
E. transparent
2 2 1Pa is:
A. 1N/m
B. 1m/N
C. 1 kg/m · s
D. 1 kg/m · s2
E. 1N/m · s
3
3-To obtain the absolute pressure from the gauge pressure:
A. subtract atmospheric pressure
C. subtract 273
B. add atmospheric pressure
D. add 273
E. convert to N/m2
4
Barometers and open-tube manometers are two instruments that are used to
measure pressure.
A. Both measure gauge pressure
B. Both measure absolute pressure
C. Barometers measure gauge pressure and manometers measure absolute
pressure
D. Barometers measure absolute pressure and manometers measure gauge
pressure
E. Both measure an average of the absolute and gauge pressures
1
5 The vessels shown below all contain water to the same height. Rank them
according to the
pressure exerted by the water on the vessel bottoms, least to greatest.
A. 1, 2, 3, 4
B. 3, 4, 2, 1
C. 4, 3, 2, 1
D. 2, 3, 4, 1
E. All pressures are the same
6 In a stationary homogeneous liquid:
A. pressure is the same at all points
B. pressure depends on the direction
C. pressure is independent of any atmospheric pressure on the upper surface
of the liquid
D. pressure is the same at all points at the same level
E. none of the above
7 7-A hydraulic lift raises a 2000-kg automobile when a 500-N force is applied to
the smaller piston. If the smaller piston has an area of 10 cm2, what is
the cross-sectional area of the larger piston?
a.
b.
c.
d.
e.
40 cm2
80 cm2
196 cm2
392 cm2
160 cm2
8 8-The water level in a reservoir is maintained at a constant level. What is the
exit velocity in an outlet pipe 3.0 m below the water surface?
a.
b.
c.
d.
e.
2.4 m/s
3.0 m/s
5.4 m/s
7.7 m/s
49 m/s
9 9-The principle of fluid pressure that is used in hydraulic brakes or lifts is
that:
A. pressure is the same at all levels in a fluid
B. increases of pressure are transmitted equally to all parts of a fluid
C. the pressure at a point in a fluid is due to the weight of the fluid above it
D. increases of pressure can only be transmitted through fluids
2
E. the pressure at a given depth is proportional to the depth in the fluid
11 10-Which of the following statements about Pascal’s principle is true?
A. It is valid only for incompressible fluids
B. It explains why light objects float
C. It explains why the pressure is greater at the bottom of a lake than at the
surface
D. It is valid only for objects that are less dense than water
E. None of the above are true
11 11-The hydraulic automobile jack illustrates:
A. Archimedes’ principle
B. Pascal’s principle
C. Hooke’s law
D. Newton’s third law
E. Newton’s second law
12 12-One piston in a hydraulic lift has an area that is twice the area of the other.
When the pressure
at the smaller piston is increased by ∆p the pressure at the larger piston:
A. increases by 2∆p
B. increases by ∆p/2
C. increases by ∆p
D. increases by 4∆p
E. does not change
13 13-A hydraulic press has one piston of diameter 2.0 cm and the other piston of
diameter 8.0cm.
What force must be applied to the smaller piston to obtain a force of 1600N at
the larger
piston?
A. 6.25N
B. 25N
C. 100N
D. 400N
E. 1600N
14 If p is a pressure and ρ is a density then p/ρ has units of:
A. m2
C. N/m2
B. m2/s2
D. kg/m2
E. m3/kg
15 15-“An object completely submerged in a fluid displaces its own volume of
fluid”. This is:
3
A. Pascal’s paradox
B. Archimedes’ principle
C. Pascal’s principle
D. true, but none of the above
E. false
16
16-Several cans of different sizes and shapes are all filled with the same liquid
to the same depth.
Then:
A. the weight of the liquid is the same for all cans
B. the force of the liquid on the bottom of each can is the same
C. the least pressure is at the bottom of the can with the largest bottom area
D. the greatest pressure is at the bottom of the can with the largest bottom area
E. the pressure on the bottom of each can is the same
17-People can snorkel down to a depth of roughly one meter. This means that
the maximum pressure their lungs can exert on the air they expel is
roughly
17
a.
b.
c.
d.
e.
9800 N.
9800 Pa.
9800 ATM.
19 600 N.
19 600 N/m2
18- What fraction of an iceberg is submerged? (ice = 917 kg/m3,
sea = 1.03 3 kg/m3.)
18
a.
b.
c.
d.
e.
95%
93%
91%
89%
77%
19 19-An A blimp is filled with 200 m3 of helium. How much mass can the
balloon lift? The density of helium is 1/7 that of air, and the density of
air is 1/800 that of water.
a.
b.
c.
d.
e.
115 kg
214 kg
315 kg
415 kg
37 kg
21
4
20- Determine the minimum area of a flat ice floe 1.0 meter thick if it is to
support a 2000-kg car above seawater. (ice = 920 kg/m3, sea = 1020
kg/m3.)
a.
b.
c.
d.
e.
20 m2
40 m2
60 m2
80 m2
100 m2
Problems
. 1-Calculate the mass of a solid iron sphere that has a diameter
1 of 3.00 cm.
2
2-A 50.0-kg woman balances on one heel of a pair of high heeled
shoes. If the heel is circular and has a radius of
0.500 cm, what pressure does she exert on the floor?
3
3-The spring of the pressure gauge shown in Figure
has a force constant of 1 000 N/m, and the piston has a
diameter of 2.00 cm. When the gauge is lowered into
water, at what depth does the piston move in by
0.500 cm?
4
4-(a) Calculate the absolute pressure at an ocean depth of
1 000 m. Assume the density of seawater is 1 024 kg/m3
and that the air above exerts a pressure of 101.3 kPa.
(b) At this depth, what force must the frame around a
5
circular submarine porthole having a diameter of
30.0 cm exert to counterbalance the force exerted by
the water?
5
5-The tank shown in Figure is filled with water to a
depth of 2.00 m. At the bottom of one of the side walls
is a rectangular hatch 1.00 m high and 2.00 m wide.
The hatch is hinged at its top. (a)
Determine the force
that the water exerts on the hatch. (b)
Find the torque
exerted about the hinges.
6
6 6-A swimming pool has dimensions 30.0 m x 10.0 m and
a flat bottom. When the pool is filled to a depth of
2.00 m with fresh water, what is the force caused by the
water on the bottom? On each end? On each side?
7
7-A cube of wood having a side dimension of 20.0 cm and
a density of 650 kg/m3 floats on water. (a) What is the
distance from the horizontal top surface of the cube to
the water level? (b) How much lead weight must be
placed on top of the cube so that its top is just level with
the water?
7
8 8-A plastic sphere floats in water with 50.0% of its volume
Submerged. This same sphere floats in glycerin with
40.0% of its volume submerged. Determine the densities
of the glycerin and the sphere
9 In a car lift used in a service station, compressed air exerts a force
on a small piston of circular cross section having a radius of r1=
5.00 cm. This pressure is transmitted by an incompressible liquid
to a second piston of radius r2= 15.0 cm. (a) What force must the
compressed air exert on the small piston in order to lift a car
weighing 13 300 N? Neglect the weights of the pistons. (b) What
air pressure will produce a force of that magnitude?
11
In a huge oil tanker, salt water has flooded an oil tank to a depth
of 5.00 m. On top of the water is a layer of oil 8.00 m deep, as in
the cross-sectional view of the tank in Figure. The oil has a
density of 0.700 g/cm3. Find the pressure at the bottom of the
tank. (Take 1 025 kg/m3 as the density of salt water.)
?
P1=P0 +oil gh1= 1.01x105 Pa+(7.00x102 kg/m3)(9.80m/s2)(8.00m)
= 1.56x105 Pa
so P bott= P1+water gh2= 1.56x105 Pa+ (1.025x103 kg/m3) )(9.80m/s2)(5.00m)
= 2.06x105 Pa
8
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