Why does the milk flow out of the glass and spread out into a thin puddle rather than staying in the glass or spreading out more across the floor?
The flow of milk out of a glass and its subsequent behavior depends on several factors, including the angle at which the glass is tilted, the surface tension of milk, and various forces acting upon it.
When you tilt a glass of milk, the force acting on the liquid is gravitational force, pulling it downward. As the milk begins to flow out of the glass, it forms a thin stream due to the cohesive forces between the milk molecules, which is the surface tension. This surface tension allows the milk to retain its shape as a stream.
As the milk falls from the glass to the floor, other forces come into play. When the milk hits the floor, it experiences an opposing force called the normal force, exerted by the surface of the floor. The normal force helps to spread the liquid outwards, as it counteracts the downward gravitational force.
Additionally, the viscosity of milk affects the manner in which it spreads. Milk is a viscous fluid, meaning it has resistance to flow. This resistance causes the milk to spread relatively slowly compared to a less viscous liquid, such as water.
The overall behavior of the milk as it spreads out into a thin puddle depends on a complex interplay between these forces and the properties of the milk itself.