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Drag Force

Drag force is the resistive force experienced by objects moving through a fluid such as air or water. It's essential for understanding motion with resistance, especially at high speeds or in fluid environments.

Formulas

• F_d = -bv — Linear drag (low-speed motion)
• F_d = -cv² — Quadratic drag (high-speed motion)
• F_d = (1/2) C_d ρ A v² — General form

Key Variables

• F_drag — Drag force (N)
• v — Velocity of object (m/s)
• b, c — Drag coefficients
• C_d — Dimensionless drag coefficient
• ρ — Fluid density (kg/m³)
• A — Cross-sectional area (m²)

Conceptual Overview

Drag force increases with velocity. At low speeds, linear drag dominates. At high speeds, like skydiving or car racing, quadratic drag becomes significant. When drag balances out the force of gravity, objects reach terminal velocity. In some circumstances, such as deploying a parachute, your drag force can exceed the gravitational force until it reaches its terminal velocity.

Real-World Examples

• Skydiver reaching terminal velocity
• Cyclists using aerodynamic helmets to reduce C_d
• Spacecraft reentry using drag to decelerate

Graph: Drag vs Velocity

Interactive Simulation

Adjust the drag coefficient and type to observe how an object falls with drag applied.