The part above middle horizontal layer (surface) is‘shortened’ and is under compression while the part below the middle surface is elongated and undre tension. thus, upper half is in ‘Comp resve stress’ while lower half is in ‘tensile stress’. (The middle surface is neutral).
Strain : When the particles of a body are displaced from their equilibrium positions under the inter mo lecular forces, the body is said to be strained. You squeez a rubber ball, it is strained. You may pull apart the ends of a wire, it is strained.
