When small insects like ants fall from a height why don't they get hurt?

Answer 1

This is a complicated question. First ask yourself what happens when you fall from a height.

Your weight pulls you down faster and faster. If you were falling where there is no air, for example on the moon, you would keep on going faster, the further you fell. Down here on Earth however, there is air, and the faster you travel through air the harder the air pushes back against your movement. We call this air resistance, or drag. To feel drag, open a window in a car at speed (travelling where it is safe to stick your hand out of the window). At low speed it feels just like a wind pushing against your hand. At high speed it pushes really hard. If you jump out of an aircraft more than a few hundred metres up in the air you will fall faster and faster until you fall so fast that the wind pushes back at you just as hard as your weight pulls you down.

When that happens you no longer fall any faster; you are travelling at what we speak of as your terminal velocity.

Another thing is that your shape affects how fast you fall through the air. If you fall through the air like a needle falling point first we say that you are streamlined and you will fall very fast before the air stops you from falling any faster. You will have a very high terminal velocity. If you are all spread out like a parachute, then you have to move huge amounts of air to fall at all, so if you have a parachute you can fall from very high without coming to harm. Then there is the question of how heavy you are. If you are heavy and streamlined than your terminal velocity will be enormous and there will be a tremendous thump when you land.

Yet another thing is how you are built; if you are soft and squashy then you probably will splash when you hit the ground. If you are very hard then you probably will crack and break, like a glass bottle falling on hard ground. If you are springy enough then you are likely to bounce without coming to much harm.

Finally, the smaller you are, then, other things being equal, the less weight you have for the amount of air you have to move.

If you don't know about squares and cubes, then just skip this paragraph. Otherwise remember this: if you are bigger, the amount of air you must move in falling through it goes up with the square of your size. (For example, if you grow three times larger in every direction, you move about nine times as much airand must push about nine times as hard just to fall at the same speed as before.) However, your weight goes up with the cube of your size. (For example if you grow three times larger in every direction, you weigh about 27 times as much as before, which means that you might expect to fall about three times faster. Things really are a little more complicated than that, but it will give you the general idea..)

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Now then, think of an ant. It is very small. It is not very heavy. It is very springy. It is not very streamlined. Take a marble and hold it high; it is fairly large (compared to an ant) and it is dense, more so than any ant, so if you drop it you can see it falling fast and it hits the ground with a thump and bounces (or breaks). Then take a scrap of tissue paper and roll it into a little ball about ant size. If you hold it high up and drop it at the same time as the marble, you will see that it will reach its terminal velocity very quickly and it will fall gently, hardly bouncing at all.

Once you have tried that, you may go out and find an ant and drop it from a height. You will find that it falls at a very modest terminal velocity and its legs are so springy and such good shock absorbers that it can hit the ground walking or running and simply go off, often without even a bounce.

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So, to sum it up: the ant is small. The ant is not streamlined; it has legs and antenna sticking out and interfering with the air flow, creating drag. The ant is light; it cannot push the air out of the way very strongly. The ant is springy; it would have to hit the ground at a very high velocity to come to any harm.

You could drop that ant from several kilometres up in the air and it would reach its terminal velocity within the first meter that it fell; all the rest of the way it would float down at the same low speed. And of course, when it finally hit solid ground it would come to no harm.

If we dropped a human, or a horse, or an elephant, from that same height they would fall at very high terminal velocities and would certainly be killed or even smashed.