Air resistance

Definition

Air resistance is the force exerted by air against the motion of an object moving through it. This force opposes the object's motion and increases with speed.

5 Must Know Facts For Your Next Test

1. Air resistance is often modeled as a drag force that is proportional to either the velocity or the square of the velocity, depending on the Reynolds number.
2. The terminal velocity of an object occurs when air resistance equals the gravitational force, resulting in zero net acceleration.
3. Air resistance depends on factors such as the object's speed, cross-sectional area, shape, and the density of the air.
4. In free fall scenarios without air resistance, objects accelerate at $9.8 \, m/s^2$, but with air resistance, they reach a terminal velocity where acceleration ceases.
5. The drag coefficient is a dimensionless number used to quantify an object's aerodynamic properties and its resistance to airflow.

Review Questions

• How does air resistance affect an object's motion during free fall?
• What factors influence the magnitude of air resistance experienced by an object?
• Explain how terminal velocity is achieved in the presence of air resistance.

Related terms

Drag Force:

A type of frictional force that opposes an object's motion through a fluid like air or water.

Terminal Velocity:

The constant speed that a freely falling object eventually reaches when the drag force equals the gravitational force.

Gravitational Force:

$F=mg$, where $m$ is mass and $g$ is acceleration due to gravity ($9.8 \, m/s^2$ near Earth's surface).