It's very unlikely to kill someone, or even seriously injure them. You should be at least as worried about playing baseball or riding a bicycle around people.
Probably on the order of 120 MPH or 55.8 meters per second. The drone weighs 1.2 Kilograms. The kinetic energy on impact would be 1800 Joules give or take. A 357 Magnum generates about 873 Joules.
The energy we are talking about is not insignificant. I'm actually in favor of allowing people to fly drones with as little restriction as possible but let's not pretend there aren't some risks.
How do you figure 120mph? It's ~1kg and I would guess has a higher surface area relative to mass than a person whose terminal velocity is about 120mph.
In any event, it takes a person 8s to get close to terminal velocity — that's a drop of 300m or so.
The energy involved is certainly non trivial but energy is not the whole story. The densest, heaviest pieces will be the battery and motors.
depends where you fly. A 2-5+ kg drone, even if the props aren't spinning is gonna do serious damage if it drops from the sky and hits someone on the head. With spinning CF props you can easily slice someone up pretty bad
