CBSE Class 11 Pressure in fluids Worksheet A

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Question. 8 mercury drops coalesce to form one mercury drop, the energy changes by a factor of
(a) 1
(b) 2
(c) 4
(d) 6

Answer: C

Question. If a water drop is kept between two glass plates, then its shape is

Answer: C

Question. The fraction of a floating object of volume V₀ and density d₀ above the surface of liquid of density d will be
(a) d₀/d-d₀
(b) d-d₀/d
(c) d₀/d
(d) d₀d/d+d₀

Answer: B

Question. Gases do not posses
(a) density
(b) surface tension
(c) volume
(d) viscosity

Answer: B

Question. A big drop of radius R is formed by 1000 small droplets of water. The radius of small drop is
(a) R/10
(b) R/100
(c) R/500
(d) R/1000

Answer: A

Question. A ring is cut from a platinum tube 8.5 cm internal and 8.7 cm external diameter. It is supported horizontally from the pan of a balance, so that it comes in contact with the water in a glass vessel. If an extra 3.97. If is required to pull it away from water, the surface tension of water is
(a) 72 dyne cm^–1
(b) 70.80 dyne cm^–1
(c) 63.35 dyne cm^–1
(d) 60 dyne cm^–1

Answer: A

Question. Paint-gun is based on
(a) Bernoulli’s theorem
(b) Archimedes’ principle
(c) Boyle’s law
(d) Pascal’s law

Answer: A

Question. A tank is filled with water upto a height H. Water is allowed to come out of a hole P in one of the walls at a depth h below the surface of water (see fig.) Express the horizontal distance X in terms H and h. 

(a) X = h √(H - h)
(b) X = √h/2(H - h)
(c) X = 2 √h (H - h)
(d) X = 4 √h (H - h)

Answer: C

Question. Which of the following diagrams does not represent a streamline flow? 

Answer: D

Question. A body of density r' is dropped from rest at a height h into a lake of density r where ρ > ρ' neglecting all dissipative forces, calculate the maximum depth to which the body sinks before returning to float on the surface :
(a) h/ρ-ρ
(b) hρ'/ρ
(c) hρ'/ρ-ρ'
(d) hρ/ρ-ρ'

Answer: C

Question. A liquid is allowed to flow into a tube of truncated cone shape. Identify the correct statement from the following.
(a) The speed is high at the wider end and high at the narrow end.
(b) The speed is low at the wider end and high at the narrow end.
(c) The speed is same at both ends in a stream line flow.
(d) The liquid flows with uniform velocity in the tube.

Answer: B

Question. A small ball (menu) falling under graivty in a viscous medium experiences a drag force proportional to the instantaneous speed u such that F_drag = Ku . Then the terminal speed of the ball within the viscous medium is
(a) K/mg
(b) mg/K
(c) √mg/K
(d) (mg/K)²

Answer: B

Question. Two capillary of length L and 2L and of radius R and 2R are connected in series. The net rate of flow of fluid through them will be (given rate to the flow through single capillary, X = πPR⁴/8ηL)
(a) 8/9 X
(b) 9/8 X
(c) 5/7 X
(d) 7/5 X

Answer: A

Question. A spherical ball of iron of radius 2 mm is falling through a column of glycerine. If densities of glycerine and iron are respectively 1.3 × 10³ kg/m³ and 8 × 10³ kg/m³. h for glycerine = 0.83 Nm^–2 sec, then the terminal velocity is
(a) 0.7 m/s
(b) 0.07 m/s
(c) 0.007 m/s
(d) 0.0007 m/s

Answer: B

Question. Water rises to a height of 10 cm in capillary tube and mercury falls to a depth of 3.1 cm in the same capillary tube. If the density of mercury is 13.6 and the angle of contact for mercury is 135°, the approximate ratio of surface tensions of water and mercury is
(a) 1 : 0.15
(b) 1 : 3
(c) 1 : 6
(d) 1.5 : 1

Answer: C

Question. 1 centipoise is equal to
(a) 1 kg m^–1 s^–1
(b) 1000 kg m^–1 s^–1
(c) 0.1 kg m^–1 s^–1
(d) 0.001 kg m^–1 s^–1

Answer: D

Question. In a satellite moving round any planet, the gravitational force is effectively balanced. If an ice cube exists there, and it melts with passage of time, its shape will
(a) remain unchanged
(b) change to spherical
(c) become oval-shaped with long-axis along the orbit plane
(d) become oval-shaped with long axis perpendicular to orbit plane

Answer: B

Question. Two non-mixing liquids of densities r and nr(n > 1) are put in a container. The height of each liquid is h. A solid cylinder of length L and density d is put in this container. The cylinder floats with its axis vertical and length pL(p < 1) in the denser liquid. The density d is equal to :
(a) {1 + (n + 1)p}r
(b) {2 + (n + 1)p}r
(c) {2 + (n – 1)p}r
(d) {1 + (n – 1)p}r

Answer: D

Question. Figure shows a weigh-bridge, with a beaker P with water on one pan and a balancing weight R on the other. A solid ball Q is hanging with a thread outside water. It has volume 40 cm³ and weighs 80 g. If this solid is lowered to sink fully in water, but not touching the beaker anywhere, the balancing weight R' will be
(a) same as R
(b) 40 g less than R
(c) 40 g more than R
(d) 80 g more than R

Answer: C

Question. Water rises to a height 'h' in a capillary tube. If the length of capaillary tube above the surface of water is made less than 'h' then : 
(a) water rises upto the top of capillary tube and stays there without overflowing
(b) water rises upto a point a little below the top and stays there
(c) water does not rise at all.
(d) Water rises upto the tip of capillary tube and then starts overflowing like fountain.

Answer: A

Question. One drop of soap bubble of diameter D breaks into 27 drops having surface tension s. The change in surface energy is
(a) 2πσD²
(b) 4πσD²
(c) πσD²
(d) 8πσD²

Answer: D

Question. In the figure, the velocity V₃ will be 

(a) Zero
(b) 4 ms^–1
(c) 1 ms^–1
(d) 3 ms^–1

Answer: C

Question. The pressure energy per unit volume of a liquid is
(a) P/ρ
(b) P
(c) P × ρ
(d) ρ/P

Answer: B

Question. An open vessel containing water is given a constant acceleration a in the horizontal direction. Then the free surface of water gets sloped with the horizontal at an angle q, given by
(a) θ = cos^-1 g/a
(b) θ = tan^-1 a/g
(c) θ = sin^-1 a/g
(d) θ = tan^-1 g/a

Answer: D

1. Does Archimedes principle hold in a vessel in a free fall?

2. Why does not the pressure of atmosphere break windows?

3. If a big drop of radius R is formed by 1000 small droplets of water, then find the radius of small drop?

4. A boulder is thrown into a deep lake. As it sinks deeper and deeper into water, does the buoyant force changes?

5. At what depth in an ocean will a tube of air have one – fourth volume it will have on reaching the surface? Given Atmospheric Pressure = 76 cm of Hg and density of Hg = 13.6g/cc?

6. Why is it painful to walk barefooted on a road covered with pebbles having sharp edges?                   

7. A liquid stands at the same level in the U – lube when at rest. If A is the area of cross section of tube and g is the acceleration due to gravity, what will be the difference in height of the liquid in the two limbs when the system is given acceleration ‘a’?

8. Two ballons that have same weight and volume contains equal amounts of helium. One is rigid and other is free to expand as outside pressure decreases. When released, which balloon will rise higher?

9. An object floats on water with 20% of its volume above the water time. What is the density of object? Given Density of water = 1000kg|m³.

10. A cubical block of iron 5cm on each side is floating on mercury in a vessel:-

1) What is the height of the block above mercury level?

2) Water is poured into vessel so that it just covers the iron block. What is the height of the water column?

Given Density of mercury = 13.6g|cm3 and Density of iron = 7.2g|cm³

Click on link below to download CBSE Class 11 Pressure in fluids Worksheet A.