Why don’t bugs die when they hit the ground once they’ve fallen from a high distance?
(An explanation of terminal velocity)
Say an ant has crawled out of its nest which is located 60 feet (20 m) above the jungle floor. Then suppose a gust of wind tips the ant over off the tree and she starts her descent towards the jungle floor. As she falls, her natural instinct is to spread her legs like a parachute to try and slow her descent towards the ground. As she falls towards the jungle floor, she starts to pick up speed and then reaches her terminal velocity of about 4 mph (6.4 km/hour), then falls to the ground unharmed or dead.
The main thing that helped our ant survive the fall, was the fact that ants, and any other small creatures, have little mass relative to their air resistance, meaning that they fall slowly and, therefore, have little energy to dissipate when they hit the ground. We must remember that it is not the fall that kills a creature, yet it is the sudden stop at the ground which will kill a creature.
Her decision to spread her legs out like a parachute also aided in her safe descent to the ground. This is because the retarding force known as air resistance. Air resistance exists because air molecules collide into a falling body creating an upward force opposite gravity. This upward force will eventually balance the falling body’s weight. It will continue to fall at constant velocity known as the terminal velocity, which will stay the same until she reaches the ground (Because she has less terminal velocity, because of her small body, she hits the ground unharmed).
Ants, like all objects falling through the atmosphere, have a terminal velocity that depends on their shape, size, and mass. An ant picks up speed as she falls through the air. The air, in turn, resists her movement with a force proportional to the square of her speed. Eventually she reaches a speed at which the upward drag forces exactly balance her downward weight and she stops accelerating. That speed is her terminal velocity.
The terminal velocity of a small to medium ant is about 4 mph (6.4 km/hour), according to the physics department of the University of Illinois. An ant would fall faster, given a ball-like shape, but the ant’s no dummy. She thrusts her legs out, presenting more surface to the air, to fall slower, like a flat sheet of paper instead of a balled-up sheet. Indeed, a man has a terminal velocity of about 125 mph (200 km/hour) with arms and legs fully extended to catch the wind like a parachute and about 200 mph (320 km/hour) when curled into a ball.
So, depending on an objects mass and terminal velocity, determines whether or not they survive a fall. As you can see, small creatures such as ants, spiders, frogs, etc have less momentum when falling from great distances and reach their terminal velocity quicker than a much larger object. This means that a small creature has less energy to dissipate when they hit the ground, oppose to a larger object having more energy to dissipate when they hit the ground.