Q1: In a singly reinforced beam

ANS:C - plane sections transverse to the centre line of the beam before bending remain plane after bending

When a beam is subjected to bending, its cross-section experiences deformation, with different parts of the cross-section undergoing different amounts of deformation. However, the assumption of plane sections remaining plane after bending asserts that any cross-section that is initially planar and perpendicular to the longitudinal axis of the beam will remain planar and perpendicular to the axis even after bending. This assumption simplifies the analysis of beam bending by allowing engineers to treat the beam as if it were composed of a series of planar cross-sections that undergo pure bending. It enables the application of basic beam bending equations, such as the Euler-Bernoulli beam theory equations, to determine the bending moments, shearing forces, and deflections along the beam's length. While the assumption is generally valid for small to moderate deformations and for beams made of homogeneous materials, it may become less accurate for highly curved beams, beams with significant deformations, or beams made of non-homogeneous materials. Overall, the assumption of plane sections remaining plane after bending greatly simplifies the analysis of beam bending behavior and is a fundamental concept in structural engineering.