ZENITH

(JEE Entrance)

Sub - Physics Mark -

Std – 12th Time -
Topic – Fluid Mechanics

1. In a hydraulic lift, used at a service station the (1)4/3

radius of the large and small piston are in the (2)3/2
ratio of 20:1. What weight placed on the small (3)3
piston will be sufficient to lift a car of mass (4)5
1500 kg? 6. A cork is suberged in water by a spring
(1)3.75 kg attached to the bottom of a bowl. When the
(2)37.5 kg bowl is kept in an elevator moving with
(3) 7.5 kg acceleration downwards, the length of spring
(4) 75 kg (1) Increases
2. Two solids A and B float in water. It is (2) Decreases
observed that A floats with half its volume (3) Remains unchanged
immersed and B floats with 2/3 of its volume (4) None of these
immersed. Compare the densities of A and B 7. A hollow sphere of volume V is floating on
(1)4:3 water surface with half immersed in it. What
(2)2:3 should be the minimum volume of water
(3)3:4 poured inside the sphere so that the sphere
(4)1:3 now sinks into the water
3. The fraction of a floating object of volume V0 (1) V/2
and density d0 above the surface of a liquid of (2) V/3
density d will be (3) V/4
𝑑0
1) 𝑑 (4) V
𝑑𝑑0 8. A tank is filled with water up to height H.
2) 𝑑+𝑑0
𝑑−𝑑0
Water is allowed to come out of a hole P in
3) 𝑑 one of the walls at a depth D below the
𝑑𝑑0
4) surface of water. Express the horizontal
𝑑−𝑑0
4. Density of the ice is p and that of water is σ. distance x in terms of H and D:
What will be the decrease in volume when a
mass M of ice melts.
𝑀
1)
𝜎−𝑝
𝜎− 𝑝
2) 𝑀
1 1
3) 𝑀 [𝑝 − 𝜎 ]
1 1 1
4) [ − 𝜎]
𝑀 𝑝
5. Two bodies are in equilibrium when
suspended in water from the arms of a (1) 𝑋 = √𝐷(𝐻 − 𝐷)
balance. The mass of one body is 36 g and its 𝐷(𝐻−𝐷)
(2) 𝑋 = √
2
density is 9 g/cc. If the mass of the other is 48
g, its density in g/cc is: (3) 𝑋 = 2√𝐷(𝐻 − 𝐷)
(4) 𝑋 = 4√𝐷(𝐻 − 𝐷)
9. A fixed cylindrical vessel is filled with water up
to height H. A hole is bored in the wall at a
 depth h from the free surface of water. For
maximum horizontal range h is equal to :
(1)H
(2)3H/4
(3) H/2
(4) H/4
10. An incompressible liquid flows through a
horizontal tube as shown in the figure. Then
the velocity 'v' of the fluid is:

(1) 3.0 m/s

(2) 1.5 m/s
(3) 1.0 m/s
(4) 2.25 m/s
11. For a fluid which is flowing steadily, the level
in the vertical tubes is best represented by

13. An ice berg of density 900 kg/m³ is floating in

water of density 1000 Kg/m³. The percentage
of volume of ice- cube outside the water is
(1)20%
(2)35%
(3) 10%
(4) 25%
14. A log of wood of mass 120 Kg floats in water.
The weight that can be put on the raft to
12. Water flows through a frictionless duct with a make it just sink, should be (density of wood-
cross- section varying as shown in fig. 600 Kg/m³)
Pressure p at points along the axis is (1) 80 Kg
represented by (2) 50 Kg
 (3) 60 Kg centre of the circular base. If the radius of the
(4) 30 Kg vessel is r and angular velocity of rotation is
15. A cylinder of height 20m is completely filled ea, then the difference in the heights of the
with water. The velocity of efflux of water (in liquid at the centre of the vessel and the edge
ms-1) through a small hole on the side wall of is
𝑟𝑤
the cylinder near its bottom, is: (1) 2𝑔
(1)10 𝑟2𝑤2
(2)20 (2) 2𝑔
(3)25.5 (3) √2𝑔𝑟𝑤
(4)5 𝑤2
(4)
2𝑔𝑟 2
16. If pressure at half the depth of a lake is equal
21. A given shaped glass tube having uniform
to 2/3 pressure at the bottom of the lake then
cross-section is filled with water and is
what is the depth of the lake
mounted off a ratable shaft as shown in
(1) 10m
figure. If the tube is rotated with a constant
(2)20m
angular velocity then
(3)60m
(4)30m
17. When a large bubble rises from the bottom of
a lake to the surface. Its radius doubles. If
atmospheric pressure is equal to that of
column of water height H, then the depth of
lake is
(1)H
(2)2H (1) water levels in both sections A and B go up
(3)7H (2) water level in section A goes up and that in
(4) 8H B comes down
18. The volume of an air bubble become three (3) water level in section A comes down and
times as it rises from the bottom of a lake to that in B goes up
its surface. Assuming atmospheric pressure to (4) water levels remain same in both sections
be 75 cm of Hg an density of water to be 1/10 22. Water flows through two identical tubes A
of the density of mercury, the depth of the and B. A volume V0, of water passes through
lake is the tube A and 2 V0 through B in a given time.
(1)5m Choose the incorrect option.
(2) 10m (1) Flow in both the tubes are steady.
(3) 15m (2) Flow in both the tubes are turbulent.
(4)20m (3) Flow is steady in A but turbulent in B.
19. A beaker containing a liquid is kept inside a (4) Flow is steady in B but turbulent in A.
big closed jar. If the air inside the jar is 23. A liquid of density 𝜌 comes out with a velocity
continuously pumped out, the will pressure in v from a horizontal tube of area of cross-
the liquid near the bottom of the liquid section A. The reaction force exerted by the
(1) Increases liquid on the tube is F. Choose the incorrect
(2) Decreases option.
(3) Remain constant (1) 𝐹 ∝ 𝑣
(4) First decrease and then increase (2) 𝐹 ∝ 𝑣 2
20. A liquid is kept in a cylindrical vessel which is (3) 𝐹 ∝ 𝐴
being rotated about a vertical axis through the (4) 𝐹 ∝ 𝜌
24. There are two identical small holes on the
opposite sides of a tank containing a liquid.
The tank is open at the top. The difference in
height between the two holes is h. As the
liquid comes out of the two holes, the tank
will experience a net horizontal force

(1) √ℎ
(2) h
(3) ℎ3/2
(4) ℎ2
25. An engine pumps water continuously through
a hose. Water leaves the hose with a velocity
v and m is the mass per unit length of the
water jet. What is the rate at which kinetic
energy is imparted to water
1
(1) 𝑚𝑣 3
2
3
(2) 𝑚𝑣
1
(3) 𝑚𝑣 2
2
1 2 3
(4) 2
𝑚 𝑣