Why falling water drops become spherical in shape Select the primary physical reason that small falling water droplets assume a nearly spherical shape.

Introduction / Context:
Naturally forming droplets (rain, sprays) are commonly spherical when small. Understanding the dominant force helps in atomization, nozzle design, and environmental modeling.

Given Data / Assumptions:

• Small droplets where aerodynamic deformation and inertia are modest.
• No electric fields or surfactants altering interfacial properties.

Concept / Approach:
A liquid surface possesses surface tension, an energetic penalty per unit area. For a given volume, the sphere has the minimum surface area. Therefore, surface tension drives a free droplet to become spherical to minimize total surface energy. Cohesion is the molecular origin of surface tension, but the macroscopic effect selecting the sphere is specifically surface tension.

Step-by-Step Solution:

Verification / Alternative check:
As drops grow larger or fall faster, they deviate from sphericity (oblate shapes, breakup) when We increases, confirming the role of surface tension vs inertia.

Why Other Options Are Wrong:
Adhesion pertains to unlike materials (liquid/solid/air interfaces) and is not the primary cause; viscosity resists rate of deformation but does not set the equilibrium shape; “cohesion” is microscopic—surface tension is the correct macroscopic descriptor.

Common Pitfalls:
Assuming all raindrops are spherical regardless of size; large raindrops become distorted and may break.

Final Answer:
surface tension minimizing surface area