21.
Sound waves in air are

22.
Magnetism at the centre of a bar magnet is

23.
It is more difficult to walk on a sandy road than on a concrete road because

24.
Find the maximum velocity for the overturn of a car moving on a circular track of radius 100 m. The co-efficient of friction between the road and tyre is 0.2

25.
Of the following properties of a wave, the one that is independent of the other is its

26.
Lux is the SI unit of

27.
On a rainy day, small oil films on water show brilliant colours. This is due to

28.
Point A is at a lower electrical potential than point B. An electron between them on the line joining them will

29.
Materials for rain-proof coats and tents owe their water-proof properties to

30.
RADAR is used for: