{"id":226,"date":"2026-06-13T16:53:14","date_gmt":"2026-06-13T16:53:14","guid":{"rendered":"https:\/\/physicsfundamentalsinfo.com\/blog\/?p=226"},"modified":"2026-06-13T16:53:16","modified_gmt":"2026-06-13T16:53:16","slug":"terminal-velocity","status":"publish","type":"post","link":"https:\/\/physicsfundamentalsinfo.com\/blog\/mechanics\/terminal-velocity\/","title":{"rendered":"What Is Terminal Velocity?"},"content":{"rendered":"\n
Definition<\/div>

\n\nTerminal velocity is the constant maximum speed a falling object reaches when the upward drag force from the air exactly balances its downward weight, leaving zero net force and zero acceleration. It depends on the object’s mass, cross-sectional area, shape and the air’s density \u2014 not on how far the object has already fallen.\n\n<\/p><\/div>\n

Step out of a plane and, for the first few seconds, you really do accelerate \u2014 the ground rushes up faster and faster. Then something odd happens. The rushing stops getting worse: you are still plummeting, yet your speed locks in and refuses to climb any higher.<\/p>\n

That ceiling is terminal velocity. It is why a skydiver, a hailstone and a falling leaf each settle into a steady descent instead of speeding up without limit, and it is the reason a parachute can save your life. The whole idea comes down to one tug-of-war: gravity pulling down, air pushing back.<\/p>\n

What Is Terminal Velocity?<\/h2>\n

Picture two forces fighting over a falling object. Gravity pulls it down with a steady force \u2014 its weight. The air shoves back with a drag force that points up, against the motion. The catch is that drag is not constant: the faster you move, the harder the air resists.<\/p>\n

At the instant of release the object is barely moving, so drag is almost nothing and gravity wins easily. As speed builds, drag grows quickly. Eventually the upward drag matches the downward weight exactly.<\/p>\n

When those two forces cancel, the net force is zero<\/strong>. By Newton’s first law, an object with no net force keeps moving at a constant velocity \u2014 it stops accelerating. That steady, top speed is the terminal velocity. The object is still falling fast; it simply cannot go any faster in those conditions.<\/p>\n\n <\/rect>\n How the forces change as an object falls<\/text>\n \n <\/circle>\n <\/line>\n <\/polygon>\n mg<\/text>\n Fd \u2248 0<\/text>\n 1 \u00b7 Just released<\/text>\n drag = 0, a = g<\/text>\n \n <\/circle>\n <\/line>\n <\/polygon>\n mg<\/text>\n <\/line>\n <\/polygon>\n Fd<\/text>\n 2 \u00b7 Speeding up<\/text>\n drag < weight, a shrinking<\/text>\n \n <\/circle>\n <\/line>\n <\/polygon>\n mg<\/text>\n <\/line>\n <\/polygon>\n Fd<\/text>\n 3 \u00b7 Terminal velocity<\/text>\n drag = weight, a = 0<\/text>\nWeight (mg) stays fixed; drag (Fd) grows with speed until the two arrows match.<\/text>\n\n<\/svg>\n

Figure 1: A falling object reaches terminal velocity the moment the growing upward drag equals its constant downward weight.<\/p>\n

Notice what terminal velocity is not<\/em>. It is not the speed of a normal free fall in a vacuum, where nothing pushes back. It needs a fluid \u2014 air, water, oil \u2014 to exist at all.<\/p>\n

The Terminal Velocity Formula<\/h2>\n

Two things set the answer: how hard gravity pulls (the weight) and how hard the air pushes (the drag). Write down the drag force, set it equal to the weight, and the speed that makes them balance drops straight out.<\/p>\n

v\u209c = \u221a( 2mg \/ (\u03c1 \u00b7 C_d \u00b7 A) )<\/div>\n

Here each symbol means:<\/p>\n