MHTCET 15 May 2024 Shift 2 Paper

Concept:Viscous force acts parallel to the interface between liquid layers.Explanation:When two liquid layers slide past each other, they have relative motion.The faster layer drags the slower layer, while the slower layer resists the faster one.This resistance is called viscous force.It acts along the common surface between the layers.Therefore, the force is tangential to the liquid surface.It is not radial or normal, because no perpendicular component is involved.Newton's law of viscosity expresses this shear stress as:$$\tau = \eta \frac{du}{dy}$$Here, $\tau$ is the shear stress, $\eta$ is the dynamic viscosity, and $\frac{du}{dy}$ is the velocity gradient perpendicular to the flow direction.Thus, the viscous force between two liquid layers is purely tangential.Answer:C. tangential to the liquid surface.