Q4 of 41 Page 268

Explain why

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

We know that according to equation of continuity


Area × velocity = constant


By closing a water tap with our fingers, the area of outlet of water jet is reduced. As a result velocity of the outlet jet increases according to the above equation of continuity.


More from this chapter

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3

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)


(b) Viscosity of gases . .. with temperature, whereas viscosity of liquids . . . with temperature (increases / decreases)


(c) For solids with elastic modulus of rigidity, the shearing force is proportional to . . . , while for fluids it is proportional to . .. (shear strain / rate of shear strain)


(d) For a fluid in a steady flow, the increase in flow speed at a constriction follows (conservation of mass / Bernoulli’s principle)


(e) For the model of a plane in a wind tunnel, turbulence occurs at a ... speed for turbulence for an actual plane (greater / smaller)

 4

Explain why

To keep a piece of paper horizontal, you should blow over, not under, it

 4

Explain why

The size of the needle of a syringe controls flow rate better than the thumb pressure exerted by a doctor while administering an injection

 4

Explain why

A fluid flowing out of a small hole in a vessel results in a backward thrust on the vessel