Drag Force on Disk Calculator

The drag force on a disk is an important concept in fluid mechanics, a sub-discipline of physics. When a disk moves through a fluid (like air or water), it experiences a retarding force called drag force. This force opposes the motion of the disk and depends on several factors, including the radius of the disk, the velocity at which it's moving, and the shear viscosity of the fluid it's moving through. In this tutorial, we'll explore the calculation and associated formula for determining this force.

Drag Force on Disk with Broadside to Flow Calculator
Drag Force on Disk Calculator Results
Drag Force (F) = F

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Example Formula

The drag force (F) on a disk moving perpendicular to its plane in a fluid can be calculated using the following formula:

F = 6πηrv
  1. F: This is the drag force, which is the force exerted by the fluid on the disk.
  2. η: This is the shear viscosity of the fluid. The units of shear viscosity are Pascal-seconds (Pa·s).
  3. r: This is the radius of the disk. The unit of radius is typically meters (m).
  4. v: This is the velocity at which the disk is moving. The unit of velocity is typically meters per second (m/s).

Who wrote/refined the formula

This formula is derived from the principles of fluid mechanics, specifically from Stokes' law, named after George Gabriel Stokes. Stokes was a physicist and mathematician who contributed significantly to the understanding of fluid dynamics. This concept is used widely not just in physics, but also in fields like engineering, geophysics, meteorology, and even in the medical field, particularly in the study of blood flow in the body.

Real Life Application

One real-life application of this principle is in the design of vehicles and aircraft. Understanding the drag force that acts on a vehicle or an aircraft as it moves through the air can help in designing more efficient, aerodynamic shapes that reduce this force and thus increase speed and reduce fuel consumption.

Key individuals in the discipline

George Gabriel Stokes, who the Stokes' law is named after, was a significant figure in this field. His work forms the basis of many calculations involving forces in fluids. Sir Isaac Newton also made substantial contributions to the field, with his formulation of the laws of motion and universal gravitation fundamentally changing our understanding of physical phenomena.

Interesting Facts

  1. The drag force on a disk concept is used in designing and manufacturing things like CDs and DVDs.
  2. Understanding this concept has led to substantial advancements in aerodynamics, leading to more efficient vehicles and aircraft designs.
  3. This principle plays a significant role in geophysics, specifically in understanding the movement of sediment particles in bodies of water.


In conclusion, the concept of drag force on a disk has wide-ranging applications and implications in various fields. Its understanding is crucial for advancing numerous technological and scientific applications. With this knowledge, we can better design objects to interact with fluids in more efficient and beneficial ways.

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