Which of the following statements can be true about the shape of the elastic curve during the deflection of the beam?
1
If shear force is zero, the shape of the elastic curve can be a straight line
2
If shear force is zero, shape of the elastic curve can be circular arc
3
If bending moment is variable, shear force exists and shape of the elastic curve is parabolic
4
If bending moment is variable, shear force need not exists and shape of the elastic curve is parabolic.