Defining Terminal Velocity
Terminal velocity is the highest constant speed a freely falling object eventually reaches. This occurs when the upward force of resistance from the medium it is falling through (like air or water) becomes equal to the downward force of gravity. At this point, the net force on the object is zero, and it stops accelerating, continuing its fall at a steady speed.
Section 2: The Forces at Play
Two primary forces act on a falling object: gravity and air resistance (or drag). Gravity is a constant force pulling the object downward. Air resistance, however, is a type of friction that opposes the object's motion and increases as the object's speed increases. As the object accelerates, the force of air resistance grows until it perfectly balances the force of gravity.
Section 3: A Skydiver Example
Imagine a skydiver jumping from a plane. Initially, they accelerate rapidly due to gravity. As their speed increases, the upward force of air resistance also increases. Eventually, this air resistance becomes equal to the skydiver's weight. At this moment, they stop accelerating and fall at a constant terminal velocity of about 120 mph (193 km/h). When they open their parachute, the larger surface area dramatically increases air resistance, causing them to slow down to a new, much safer terminal velocity.
Section 4: Why Terminal Velocity Matters
Understanding terminal velocity is crucial in many fields, including aerodynamics, engineering, and physics. It dictates the design of parachutes, spacecraft re-entry vehicles, and even affects the size of raindrops. The concept explains why objects of different shapes and sizes can fall at different rates, even if they have the same mass.