21.
The atmospheric air is held to the Earth by :

22.
The pressure of a fluid varies with depth h as P = PQ+pgh, where p is the fluid density. This expression is associated with

23.
A parachute descends slowly whereas a stone dropped from the same height falls rapidly, because

24.
Why does bleeding occur through the nose in high mountainous regions ?

25.
Which of the following instruments is used to measure humidity ?

26.
Anemometer is an instrument meant for measuring ________

27.
A fountain pen works on the principle of

28.
A barometer is kept inside a bell jar. Air is slowly pumped out of the jar.

29.
The temperature at which water boils depends mainly on