resonance is a frequency level of any rotating body or oscillating body, if normal frequency of any rotating body approaches towards the natural frequency of it's own it leads to rising of resonance . At this level maximum vibration occure in body(i.e. shaft) which leads to bending , twisting and damaging of body.

let w_{i }**is any normal frequency of any rotating body(i.e Shaft) and W**_{n} be its natural frequency.

**then , for satisfying resonance condition ,**

**w**_{i}=Wn (Resonance)

**where W**_{n}=(k/m)^{0.5}
- w= rotating frequency (from X= xsinwt)