Drag Force and Terminal Speed

Drag force is an undesirable force that opposes the motion of an object through a fluid like air or water.

For smaller, slowly moving objects, the drag force is proportional to the object's speed.

For larger and faster-moving objects, the drag force depends on the square of the object's speed, the fluid density, the object's cross-sectional area, and the drag coefficient.

As a result of drag force, an object falling freely in a fluid does not exhibit constant acceleration.

Applying Newton's second law, the forces acting on the object are gravitational and drag, ignoring the buoyant force.

As the object falls, its speed increases, and as a result, the drag force also increases until it balances the gravitational force, resulting in zero net force and acceleration.

The highest constant speed at this point is called the terminal speed, which depends on the object's mass, shape, and surface area and the density of the fluid it is falling through.

For this reason, heavier objects have a higher terminal speed and fall faster.