Free-Fall Drop Time, Impact Speed, and Energy
How fast a dropped tool or part hits, and with how much energy - the dropped-object (DROPS) hazard.
Example
You enter
- Drop height h (ft) 50
- Object weight W (lb, optional for energy) 5
You get
- Impact speed (fps) 56.72
- Time to fall 1.76 s
- Impact energy 250 ft-lbf
Details, formula, and sources
Still air: impact speed v = sqrt(2 g h), fall time t = sqrt(2 h/g), impact energy KE = W h. A 5 lb tool dropped 50 ft hits at 39 mph with 250 ft-lbf after 1.8 s - easily fatal, the reason for hard hats, toe boards, tethers, and a cleared drop zone. Speed grows with the square ROOT of height (fast then slow) while energy grows in direct proportion. Air drag (terminal velocity), the impact deceleration force, and a horizontal launch are separate. A safety-planning estimate; the competent person and the site safety plan govern.
v = sqrt(2 g h); t = sqrt(2 h/g); KE = W h (= m g h); g = 32.174 ft/s^2. v_mph = v_fps x 0.6818.
The free-fall relations v = sqrt(2 g h), t = sqrt(2 h/g), and the impact energy KE = W h (standard kinematics; energy conservation), by name.
The free-fall relations are standard published kinematics; the drop height and object weight are the user's inputs.
Estimate. AHJ and licensed professional govern.
Field names used by the API: drop_height_ft, object_weight_lb, impact_speed_fps, fall_time_s, impact_energy_ftlb
- Free fall v = sqrt(2 g h), t = sqrt(2 h/g), KE = W h; still airkinematics / energy conservation
- No drag neglects air resistance (terminal velocity); optimistic for a light or bluff objectscope of this tile
- Scope impact deceleration force, horizontal launch, and bounce are separatescope of this tile