Terminal Velocity (Aerodynamic Drag)

ScopeV_t = sqrt(2 W/(rho_mass Cd A)), rho_mass = (air weight density)/g. A 180 lb skydiver at 7 ft^2 and Cd 0.7 terminals at the familiar 120 mph; a compact 5 lb tool near 140 mph, so over a short jobsite drop it is still accelerating (free-fall is right), but a sheet of plywood or a person tops out and falls no faster no matter the height. Heavy, compact, slick objects fall fast; light, bluff ones settle slowly. It also gives the time and fall distance to reach 95% of terminal from rest (a 180 lb skydiver: about 10 s and 1,100 ft); tumbling and altitude density change are separate. Pairs with the free-fall drop and the drag force. A planning estimate; field conditions govern.

Formula or tablerho_mass = rho_weight/g; V_t = sqrt(2 W/(rho_mass Cd A)) (drag balances weight, W = 1/2 rho V^2 Cd A). g = 32.174 ft/s^2.

Source and editionThe terminal-velocity balance W = 1/2 rho V^2 Cd A solved for V (standard fluid mechanics), by name; the drag-limited counterpart to free-fall-drop.

Free accessThe terminal-velocity relation is a standard published fluid-mechanics result; the weight, frontal area, drag coefficient, and air density are the user's inputs.

What governsEstimate. AHJ and licensed professional govern.

API field namesweight_lb, frontal_area_ft2, drag_coefficient, air_density_lb_ft3, terminal_velocity_fps, terminal_velocity_mph

• Balance V_t = sqrt(2 W/(rho_mass Cd A)), drag equals weight at terminalfluid mechanics
• Constant Cd steady terminal for a constant drag coefficient in still airscope of this tile
• Scope distance/time to reach terminal, tumbling, and altitude density change are separatescope of this tile