You are drinking water through a straw in an open glass....

Name: Problem 38, Chapter 10: College Physics
Uploaded: 2020-06-11T01:17:49-08:00
Duration: 2 min 56 s
Channel: Surjit Tewari
Description: You are drinking water through a straw in an open glass. Select a small volume of water in the straw as a system and draw a force diagram for the water in- side this volume that explains why the water goes up the straw.

You are drinking water through a straw in an open glass. Select a small volume of water in the straw as a system and draw a force diagram for the water in- side this volume that explains why the water goes up the straw.

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Key Concepts

Fluid Pressure

This concept explains that fluids exert pressure in all directions. In the context of a straw, the water experiences pressure both from above and below, and understanding how these pressures vary is key to explaining why the water moves upward.

Pressure Differential

The idea of a pressure differential is central to fluid movement. By reducing the pressure at the top of the straw (through suction), a difference is created between the lower pressure inside the straw and the atmospheric pressure acting on the water outside, resulting in a net upward force.

Forces and Free Body Diagram

Selecting a small volume of water as a system and drawing a free body diagram helps visualize the forces acting on it. This includes the upward force due to the external atmospheric pressure and the opposing forces such as internal pressure gradients and gravitational force, clarifying the net effect that leads to water rising in the straw.

Hydrostatic Equilibrium

Hydrostatic equilibrium involves a balance between gravitational forces and pressure forces in a fluid. In the straw, the balance is disrupted by the suction-induced pressure drop, which causes the forces to become unbalanced and the water to be pushed upward until a new equilibrium is reached.

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