How many frogs have to fall on you at once from out of the sky before you die?
I guess that depends on how big they are, and their terminal velocity (or at least, velocity at impact).
So, remembering that kinetic energy is Mass x velocity ^2, and that an average frog weighs (let’s be generous here and say they are cane toads) around 100g each.
with a surface area of (let’s round off here to only consider those areas of head and shoulders subject to vertical attack from falling frogs) around 0.25 m^2, lets say a maximum of 20 frogs can land at once. So, that’s around 2 kg, given the average weight of 100g.
What velocity would the frogs need to fall at so that the human would stand a 50% chance of dying? Would this be slower or faster than an estimated terminal velocity of 10 m/s for small animals (don’t consider if the frogs have adopted gliding positions).
You should include in your answer, considerations of the impact impulse, differences in skull vs shoulder elastic rebound, and whether or not the frogs are moving fast enough to generate dangerous temperature levels due to atmospheric friction.
A frog usually don’t weight very much, and since they are not very dense either, their terminal velocity is probably pretty slow. The low density ensures that the bigger they are the more drag slows them down, since terminal velocity is:
v = √((2mg)/(ρAC))
m = mass of the falling object。 A typical frog weighs about 22.7g
g = the acceleration due to gravity. On Earth it’s about 9.8 m/s²
ρ = the density of the fluid the object is falling through. On Earth the average over the distance of falling is about 1kg/m³
A = the projected area of the object. A frog of 22.7g typically is has a cross-section around 100cm², which is 0.01m²
C = the drag coefficient. A frog probably would want to balance itself while falling, as they do naturally while leaping. I’m assuming it’s about a little larger than a small bird, which would be 0.5
So the terminal velocity would be a little less than 300 m/s. The kinetic energy (Eκ = ½mv²) is 1.01kJ. At this force their surface area wouldn’t be able to penetrate our skin, and it’s not enough force to kill us either.
The largest frog weighs 3.25 kg, now that is probably another story.
Oh please don’t remind me. We had them coming at us, my poor Toto and I, like something out of Constantine. Toto was almost dragged down from the weight of a blanket of roaches. The horror, the horror!
OP might be right. When the locusts were in Africa, I figured it’d be a good source of protein to replace the veggies lost to them. If they’re coming to Asia, that’ll make two continents that are in trouble/getting their main protein from locusts.
Feels pretty biblical to me. First, a coronavirus, then a swarm of locusts to eat all the crops followed by famine. Then, rains and winds. Then wildfires. Then, the oceans rise to swallow up the human race. Pretty much on par with climate scientists’ predictions/things that are already happening…
