Explain why (c) Surface tension of a liquid is independent of the area of the surface

Explain why (d) Water with detergent disolved in it should have small angles of contact.

A plane is in level flight at constant speed and each of its two wings has an area of $25 m^2$. If the speed of the air is 180 km/h over the lower wing and 234 km/h over the upper wing surface, determine the plane’s mass. (Take air density to be $1 kg m^{-3}$).

The cylindrical tube of a spray pump has a cross-section of $8.0 cm^2$ one end of which has 40 fine holes each of diameter 1.0 mm. If the liquid flow inside the tube is $1.5 m min^{-1}$, what is the speed of ejection of the liquid through the holes ?

A vertical off-shore structure is built to withstand a maximum stress of $10^9$ Pa. Is the structure suitable for putting up on top of an oil well in the ocean ? Take the depth of the ocean to be roughly 3 km, and ignore ocean currents.

Explain why (e) A drop of liquid under no external forces is always spherical in shape

Mercury has an angle of contact equal to $140^{\circ}$ with soda lime glass. A narrow tube of radius 1.00 mm made of this glass is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside ? Surface tension of mercury at the temperature of the experiment is $0.465 N m^{-1}$. Density of mercury = $13.6 \times 10^3 kg m^{-3}$.

Explain why (a) To keep a piece of paper horizontal, you should blow over, not under, it

Explain why (b) When we try to close a water tap with our fingers, fast jets of water gush through the openings between our fingers

In deriving Bernoulli’s equation, we equated the work done on the fluid in the tube to its change in the potential and kinetic energy. (a) What is the largest average velocity of blood flow in an artery of diameter $2 \times 10^{-3} m$ if the flow must remain laminar ?

Does it matter if one uses gauge instead of absolute pressures in applying Bernoulli’s equation ? Explain.

Fill in the blanks using the word(s) from the list appended with each statement: (a) Surface tension of liquids generally . . . with temperatures (increases / decreases)

Can Bernoulli’s equation be used to describe the flow of water through a rapid in a river ? Explain.

Explain why (b) Atmospheric pressure at a height of about 6 km decreases to nearly half of its value at the sea level, though the height of the atmosphere is more than 100 km

During blood transfusion the needle is inserted in a vein where the gauge pressure is 2000 Pa. At what height must the blood container be placed so that blood may just enter the vein ? [Use the density of whole blood from Table 10.1].

What is the pressure inside the drop of mercury of radius 3.00 mm at room temperature ? Surface tension of mercury at that temperature (20 °C) is $4.65 \times 10^{-1} N m^{-1}$. The atmospheric pressure is $1.01 \times 10^5 Pa$. Also give the excess pressure inside the drop.

Explain why (e) A spinning cricket ball in air does not follow a parabolic trajectory

A 50 kg girl wearing high heel shoes balances on a single heel. The heel is circular with a diameter 1.0 cm. What is the pressure exerted by the heel on the horizontal floor ?

Explain why (c) Hydrostatic pressure is a scalar quantity even though pressure is force divided by area.

Figure 10.24 (a) shows a thin liquid film supporting a small weight = $4.5 \times 10^{-2} N$. What is the weight supported by a film of the same liquid at the same temperature in Fig. (b) and (c) ? Explain your answer physically.