Mechanical Properties of Fluids · Question 24

Water rises to a height h in capillary tube. If the length of capillary tube above the surface of water is made less than h, then

1. water rises upto a point a little below the top and stays there.
2. water does not rise at all.
3. water rises upto the tip of capillary tube and then starts overflowing like a fountain.
4. water rises upto the top of capillary tube and stays there without overflowing.

A wind with speed 40 m/s blows parallel to the roof of a house. The area of the roof is 250 m2. Assuming that the pressure inside the house is atmospheric pressure, the force exerted by the wind on the roof and the direction of the force will be ( air = 1.2 kg/m3)

1. 2.4 105 N, upwards
2. 2.4 105 N, downwards
3. 4.8 105 N, downwards
4. 4.8 105 N, upwards

A certain number of spherical drops of a liquid of radius r coalesce to form a single drop of radius R and volume V. If T is the surface tension of the liquid, then

1. energy = 4VT ( 1r - 1R ) is released.
2. energy = 3VT ( 1r + 1R ) is absorbed.
3. energy = 3VT ( 1r - 1R ) is released.
4. energy is neither released nor absorbed.

The wettability of a surface by a liquid depends primarily on

1. density
2. angle of contact between the surface and the liquid
3. viscosity
4. surface tension

A fluid is in streamline flow across a horizontal pipe of variable area of cross section. For this which of the following statements is correct?

1. The velocity is maximum at the narrowest part of the pipe and pressure is maximum at the widest part of the pipe.
2. Velocity and pressure both are maximum at the narrowest part of the pipe.
3. Velocity and pressure both are maximum at the widest part of the pipe.
4. The velocity is minimum at the narrowest part of the pipe and the pressure is minimum at the widest part of the pipe.