Question

As a result of a distant explosion, an observer first senses a ground tremour, then hears the explosion. What accounts for this time lag?

Answer 1

The speed of sound in any medium is given by Sir Newton as ,

$v=\sqrt{E/\rho }$

where E=E= coefficient of elasticity of medium ,

ρ=ρ= density of medium ,

as solids are most elastic and gases are least elastic i.e. $E_s>E_l>E_g$ ,

therefore speed of sound in solids is maximum and in gases is minimum i.e. $v_s>v_l>v_g$ .

As ground is solid therefore sound travels faster through ground than through air and an observer first senses a ground tremour than hears the explosion .