The wettability of a surface by a liquid depends primarily on

• viscosity

• surface tension

• density

• density

If dimensions of critical velocity v_c of a liquid flowing through  a tube are expressed as  are the coefficient of viscosity of liquid, density of liquid and radius of the tube respectively, then the values of x, y and z are given by

• 1,-1,-1

• -1,-1,1

• -1,-1,-1

• -1,-1,-1

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

• water rises upto the tip of the capillary tube and then starts overflowing like a fountain

• water rises  upto the top of capillary tube and stays there without overflowing 

• water rises upto a point little below the top and stays there

• water rises upto a point little below the top and stays there

84.

A U tube with both ends open to the atmosphere is partially filled with water. Oil, which is immiscible with water, is poured into one side until it stands at a distance of 10 mm above the water level on the other side. Meanwhile, the water rises by 65 mm from its original level (see diagram). The density of the oil is

• 650 kg m^–3

• 425 kg m^–3

• 800 kg m^–3

• 800 kg m^–3

A steam of a liquid of density ρ flowing horizontally with speed v rushes out of a tube of radius r and hits a vertical wall nearly normally. Assuming that the liquid does not rebound from the wall, the force exerted on the wall by the impact of the liquid is given by

• πrρv

• πrρv²

• πr²ρv

• πr²ρv²

A wide hose pipe is held horizontally by a fireman. It delivers water through a nozzle at one litre per second. On increasing the pressure. this increases to two litres per second. The firman has now to

• push forward twice as hard

• push forward four times as hard

• push backward four times as hard

• push backward twice as hard

A liquid is allowed into a tube of truncated cone shape. Identify the correct statement from the following.

• The  speed is high at the wider end and low at the narrow end

• The speed is low at the wider end and high at the narrow end.

• The speed is same at both ends in a streamline flow.

• The liquid flows with the uniform velocity in the tube.

Mercury boils at 367° C. However, mercury thermometers are made such that they can measure temperature upto 500°C. This is done by

• maintaining vacuum above mercury column in the stem of the thermometer.

• filling nitrogen gas at high pressure above the mercury column.

• filling oxygen gas at a high pressure above mercury column.

• filling nitrogen gas at a low pressure above the mercury column.

Two identical glass spheres filled with air are connected by a horizontal glass tube. The glass tube contains a pellet of mercury at its mid-point. Air in one sphere is at 0°C and the other is at 20°C. If both the vessels are heated through 10°C, then neglecting the expansions of the bulbs and the tube.

• the mercury pellet gets displaced towards the sphere at a lower temperature.

• The mercury pellet gets displaced towards the sphere at a higher temperature

• The mercury pellet does not get displaced at all.

• the temperature rise causes the pellet to expand with any displacement.

Water rises in a capillary upto a extension height such that upward force of surface tension balances the force of 75 x 10^-4 N due to weight of water. If surface tension of water is 6x10^-2 N/m.The internal circumference of the capillary must be

• 12.5$\times {10}^{-2}$m

• 6.5$\times {10}^{-2}$m

• 0.50$\times {10}^{-2}$m

• 1.25$\times {10}^{-2}$m