# Ask a Physicist Answers

## It was my understanding that the velocity of an object falling through air has to do with gravity and wind resistance only. Does the object's velocity have anything to do with its weight or mass? - JVN, Brisbane, Australia

Once the skydiver reaches its terminal velocity, the forces acting on it cancel each other out. We know that an object cannot accelerate without a net force, so that is why it then falls at a constant speed!

When an object falls a long distance through air, it eventually reaches a maximum downward velocity known as its terminal velocity. At terminal velocity, the upward force of wind resistance exactly balances the object's downward weight and it coasts downward at a steady speed. Although gravity hasn't disappeared, the object doesn't accelerate downward anymore.

Different objects have different terminal velocities. A fluffy object that catches the wind strongly but has little weight descends slowly because forces of wind resistance and weight balance one another at a low speed. A dense, compact object descends quickly because it must moves extremely fast through the air before wind resistance balances its weight.

So to answer your question, an object's terminal velocity depends directly on wind resistance and weight. However, an object's weight depends on the strength of gravity and on the object's mass-the more mass the object has or the stronger the gravity acting on it, the more the object weighs. Therefore, an object's terminal velocity depends on all four concepts: wind resistance, weight, gravity, and mass.

Answered by Louis A. Bloomfield of the University of Virginia