Young's modulus can be thought of as the spring constant for solids. Consider an ideal rod (or bar) of length and cross-sectional area . Suppose we apply a force to the face of area , causing a displacement along the axis of the rod. Then Young's modulus is given by
For wood, Young's modulus is on the order of N/m . For aluminum, it is around (a bit higher than glass which is near ), and structural steel has .