Multiple Choice QuestionsThe potential energy of a molecule on the surface of a liquid compared to one inside the liquid is
zero
lesser
equal
greater
Aerofils are so designed that the speed of air
on top side is more than on lower side
on top side is less than on lower side
is same on both sides
is turbulent
Two glass plates are separated by water. If surface ension of water is 75 dyne/cm and area of each plate wetted by water is 8 cm2 and the distance between the plates is 0.12 mm, then the force applied to separate the two plates is
102 dyne
104 dyne
105 dyne
106 dyne
The neck and bottom of a bottle are 3 cm and 15 cm in radius respectively. If the cork is pressed with a force 12 N in the neck of the bottle, then force exerted on the bottom of the bottle is
30 N
150 N
300 N
600 N
A square wire frame of size L is dipped in a liquid. On taking out a membrane is formed. If the surface tension of liquid is T, then force acting on a frame will be
2T L
4T L
8T L
16T L
64 spherical rain drops of equal size are falling vertically through air with a terminal velocity 1.5 ms-1 .If these drops coalesce to form a big spherical drop, then terminal velocity of big drop is
8 ms-1
16 ms-1
24 ms-1
32 ms-1
The equation of a wave is y = 5 sin ; where x is in cm and t is in second. The maximum velocity of the wave will be
1 ms-1
2 ms-1
1.5 ms-1
1.25 ms-1
If there were no gravity, which of the following will not be there for a fluid?
Viscosity
Surface tension
Pressure
Archimedes' upward thrust
The cylindrical tube of a spray pump has a cross-section of 8 cm2 , one end of which has 40 fine holes each of area 10-8 m2. If the liquid flows inside the tube with a speed of 0.15 m min-1 the speed with which the liquid is ejected through the holes is
50 m/s
5 m/s
0.05 m/s
0.5 m/s
B.
5 m/s
One of the fundamental principles used in the analysis of uniform flow is known as continuity of flow. This principle is derived from the fact that mass is always conserved in fluid systems regardless of the pipeline complexity or direction of flow.
According to the equation of continuity,
Q = A1 V1 = A2 V2
a v = constant ... (i)
Where Q is the volumetric flow rate
A is the cross-sectional area of flow
V is the mean velocity
Area of cross secrction of the spray pump,
a1 = 8 cm2 = 8 × 10-4 m2
number of holes n = 40
v1 = 0.15 m min-1 =
∴ For tube,
= a1 v1
For holes,
= a2 v2
According to law of continuity from equation (i)
∴ a2 v2 = a1 v1
∴ 40 × 10-8 × v =
⇒ v =
⇒ v = 5 m/s
Horizontal tube of non-uniform cross-section has radii of 0.1 m and 0.05 m respectively at M and N. For a streamline flow of liquid, the rate of liquid flow is
changing continuously with time
greater at M than at N
greater at N than at M
same at M and N
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