Re:U.S. proposes to allow drone operation at night, over people
by leetcrew on Tuesday January 15, 2019 @08:30AM
(#18910973)
a 9mm bullet can only go so high because it leaves the barrel at a much greater speed than its terminal velocity in freefall. 9mm in particular has a fairly low terminal velocity; if it falls straight down it is unlikely to seriously hurt an adult.
Re:U.S. proposes to allow drone operation at night, over people
by hashkb on Monday January 14, 2019 @07:28PM
(#18907915)
The bullet, falling from the same height as a crashing drone, is at least as lethal if it strikes a human. There is no "safe weight" for a falling object... but there may be a "safe momentum".
Re:U.S. proposes to allow drone operation at night, over people
by ricardobeat on Monday January 14, 2019 @07:50PM
(#18908005)
The proposed flying zone for drones like these is between 60-120m height. Seems like a bullet must travel at least 62m/s to penetrate human skin [1], for which you need a height of at least ~200m [2]. So even dropping a bullet from one the delivery drones would not carry a high risk of fatal injuries.
That, and P=MV, momentum/energy increases proportionally to mass. A 'safe weight' can be defined if the altitude is known.
[1] https://slate.com/news-and-politics/2011/03/can-falling-bull...
A bullet does damage because it holds a lot more energy from being accelerated - a 9mm bullet will go around a mile up before falling down (source: MythBusters). Two 500g boxes dropped from a likely much lower height will have a similar effect (concussion?) when dropped on a pedestrian regardless of the contents, except for a few outliers. Even for small, heavy objects (like a 1kg camera lens) the load would be spread by its enclosure unless it separates mid-fall.