Question

the velocity of sound is generally greater in solids than gases at N.T.P why?

Answer 1

velocity of sound depends on the bulk modulus B of the substance and the density d.

v = K √(B/d)  ,    K  = some constant

For Solids Bulk modulus is very very high as it is very dense, rigid and strong. The density is also high.  For liquids and gases Bulk modulus is not that high. For gases the Bulk modulus is equal to pressure.

Sound requires a medium for propagation. It propagates by transferring energy and vibration from one molecule to another. If the elastic properties are high, the density is high, then the disturbance propagates much faster.

Also in solids the molecules are rigidly held at their positions. So they vibrate much faster and retain the energy for longer duration of time too.

Answer 2

In solids, atoms are arranged closer to each other.