Past Questions — 2026

Young’s modulus (modulus of elasticity) is defined as the ratio of normal/tensile stress to corresponding tensile strain within the elastic limit: E = tensile stress / tensile strain. Hence option (a) is correct. Option (b) is incorrect because shear stress / shear strain is the definition of modulus of rigidity (shear modulus). Option (c) is incorrect because it mixes tensile stress with shear strain, which is not a standard elastic modulus. Option (d) is incorrect because shear stress / tensile strain also combines unlike quantities and does not define Young’s modulus.

Step-by-step reasoning: 1. **Definition of Static Water Level (SWL):** In groundwater hydrology, the static water level is the level at which water stands in a well when there is no pumping occurring (the well is in equilibrium with the surrounding aquifer). It is typically measured as the vertical distance from the ground surface down to the water surface in the well. 2. **Evaluating Option b (Drawdown):** Drawdown is the difference between the static water level and the pumping water level. It represents the drop in water level caused by the extraction of water. 3. **Evaluating Option c (Piezometric surface):** The piezometric surface is an imaginary surface that represents the total head of water in a confined aquifer. While the SWL in a piezometer reflects this surface, the specific term for the level in a well before pumping is the static water level. 4. **Evaluating Option d (Pumping water level):** This is the level to which the water drops in the well while the pump is operating. Conclusion: Since the question specifies the level 'before pumping starts', the correct term is the Static Water Level.