VISUAL PHYSICS ONLINE

2 DYNAMICS

P20 017

Sky divers usually reach terminal velocity before opening their parachutes.

A. What is meant by terminal velocity?

B. Explain why a sky diver falling freely will eventually reach terminal velocity.

C. The terminal velocity v_T of a person falling freely through the air is given approximately by the equation

where m is the mass of the person, g is the acceleration due to gravity and is a constant of value about 0.250 kg.m^-1.

Calculate the terminal velocity reached by an 80 kg skydiver.

View solution below only after you have completed the answering the question.

Solution

The forces acting on the sky diver are the gravitational force and the drag force due to the motion through the air. The drag force for a skydiver to a good approximation is proportional to the square of the speed of the skydiver. Hence, as the speed increases, the drag force increases in magnitude until the magnitude of the drag force and the magnitude of the gravitational force are equal. When this situation arises, the acceleration of the skydiver becomes zero and the person will fall with a constant velocity which is called the terminal velocity.