# Fluids - Chapter No 13

Right Answers have been shown below in red color.

1. All fluids are:

A. gases
B. liquids
C. gases or liquids
D. non-metallic
E. transparent

2. Gases may be distinguished from other forms of matter by their:

A. lack of color
B. small atomic weights
C. inability to form free surfaces
D. ability to flow
E. ability to exert a buoyant force

3. 1 Pa is:

A. 1 N/m
B. 1 m/N
C. 1 kg/m · s
D. 1 kg/m · s2
E. 1 N/m · s

4. Mercury is a convenient liquid to use in a barometer because:

A. it is a metal
B. it has a high boiling point
C. it expands little with temperature
D. it has a high density
E. it looks silvery

5. To obtain the absolute pressure from the gauge pressure:

A. subtract atmospheric pressure
B. add atmospheric pressure
C. subtract 273
E. convert to N/m2

6. 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

7. To measure moderately low pressures oil with a density of 8.5 × 102 kg/m3 is used in place of mercury in a barometer. A change in the height of the oil column of 1.0 mm indicates a change in pressure of about:

A. 1.2 × 10-7 Pa
B. 1.2 × 10-5 Pa
C. 0.85 Pa
D. 1.2 Pa
E. 8.3 Pa

8. The pressure exerted on the ground by a man is greatest when:

A. he stands with both feet flat on the ground
B. he stands flat on one foot
C. he stands on the toes of one foot
D. he lies down on the ground
E. all of the above yield the same pressure

9. 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

10. 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

11. Which of the following five statements, concerning the upper surface pressure of a liquid, is FALSE?

A. It is independent of the surface area
B. It is the same for all points on that surface
C. It would not increase if the liquid depth were increased
D. It would increase if the liquid density were increased
E. It would increase if the atmospheric pressure increased

12. 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

13. An airtight box, having a lid of area 80 cm2, is partially evacuated. Atmospheric pressure is 1.01 × 105 Pa. A force of 600 N is required to pull the lid off the box. The pressure in the box was:

A. 2.60 × 104 Pa
B. 6.35 × 104 Pa
C. 7.50 × 104 Pa
D. 1.38 × 105 Pa
E. 1.76 × 105 Pa

14. A closed hemispherical shell of radius R is filled with fluid at uniform pressure p. The net force of the fluid on the curved portion of the shell is given by:

A. 2πR2p
B. πR2p
C. 4πR2p
D. (4/3)πR2p
E. (4/3)πR3p

15. The diagram shows a U-tube with cross-sectional area A and partially filled with oil of density ρ. A solid cylinder, which fits the tube tightly but can slide without friction, is placed in the right arm. The system is in equilibrium. The weight of the cylinder is: A. ALρg
B. L3ρg
C. Aρ(L + h)g
D. Aρ(L − h)g
E. none of these

16. The density of water is 1.0 g/cm3. The density of the oil in the left column of the U-tube shown below is: A. 0.20 g/cm3
B. 0.80 g/cm3
C. 1.0 g/cm3
D. 1.3 g/cm3
E. 5.0 g/cm3

17. A uniform U-tube is partially filled with water. Oil, of density 0.75 g/cm3, is poured into the right arm until the water level in the left arm rises 3 cm. The length of the oil column is then:

A. 2.25 cm
B. 8 cm
C. 6 cm
D. 4 cm
E. need to know the cross-sectional area of the U-tube

18. A long U-tube contains mercury (density = 14 × 103 kg/m3). When 10 cm of water (density= 1.0 × 103 kg/m3) is poured into the left arm, the mercury in the right arm rises above its original level by:

A. 0.36 cm
B. 0.72 cm
C. 14 cm
D. 35 cm
E. 70 cm

19. A bucket of water is pushed from left to right with increasing speed across a horizontal surface. Consider the pressure at two points at the same level in the water.

A. It is the same
B. It is higher at the point on the left
C. It is higher at the point on the right
D. At first it is higher at the point on the left but as the bucket speeds up it is lower there
E. At first it is higher at the point on the right but as the bucket speeds up it is lower there

20. A bucket resting on the floor of an elevator contains an incompressible fluid of density ρ. When the elevator has an upward acceleration of magnitude a the pressure difference between two points in a fluid separated by a vertical distance ∆h, is given by:

A. ρa∆h
B. ρg∆h
C. ρ(g + a)∆h
D. ρ(g − a)∆h
E. ρga∆h