The terminal velocity of an object in freefall is the constant speed it reaches when the force of gravity pulling it downward is balanced by the opposing force of air resistance, and this happens when the net force on the object is zero. In SI units, the formula for the terminal velocity of an object in freefall is as follows:
where,
- is the terminal velocity (in meters per second, m/s).
- is the mass of the object (in kilograms, kg)
- is the acceleration due to gravity, (which is approximately 9.81 m/s2 on the surface of the Earth, but may vary with increasing altitude or even in another celestial body)
- is the density of the fluid (in kilograms per cubic meter, kg/m³) (For air at sea level, is approximately 1.225 kg/m3
- is the cross-sectional area of the object perpendicular to the direction of motion (in square meters, m²)
- is the drag coefficient, which is a dimensionless number determined experimentally for the specific object’s shape.
The formula provides the terminal velocity of the object in meters per second (m/s) based on these parameters and assumes that the object has reached its terminal velocity and that the forces of gravity and air resistance are balanced.
It’s important to note that the actual terminal velocity an object can achieve depends on its specific characteristics, such as its mass, shape, and the properties of the fluid (e.g., air) it is falling through.