physics question

I’m sure anyone reading this has seen the demonstration of two balls of different masses (focus people:p) being dropped from a high place only to show that they fall at the same rate. But to drop -say a feather and a bowling ball can change the outcome greatly (a bit of wind resistance)… I am wondering, were I to be tiny as an ant -would the same amount of downward force apply to me as to a dinosaur?
Yes, I know some about gravity -not alot (which is why I’m here)

What I’m getting at is, if I were small, very small, would gravity have less of an effect on my body; something like walking on the moon? Is it why insects so often can pull off such enormous feats of strength and jumping large distances?
Because to compare what they can do for their size to a person of our size would be in many cases considered “super-human”.

Any physics pros out there that can enlighten me some things? If you didn’t find a question in that stack of words above, then just do your best to form one yourself and should I need to clarify things further I will as the answers roll in. Thanks.

There’s a famous experiment where you drop a feather and a weight and they fall at different rates, but then you repeat the experiment in a vacuum and they fall at the same rate. No air resistance means that the same forces act on both objects. There’s a real version of this experiment at the Boston Museum of Science, and I’m sure it’s elsewhere, too.
T%he same acceleration due to gravity acts on an ant and on a dinosaur, but since they have different masses, the overall force of gravity acting on the dinosaur is much, much larger than that acting on the ant. This is why a dinosaur can stepo on an ant and squash it, but why an any won’t squash a dinosaur by stepping on it. It also explains why forces like static electricity, surface tension, and adhesion are so much more important to an ant than a dinosaur, and why you don’t see many dinosaurs walking up walls. It explain why the ant is built the way it is and a dinosaur the way it is. An ant scaled up to dinosaur size would collapse under the weight of its exoskeleton and its internal organs would probably be oxygen-starved, whereas a dinosaur scaled down to ant proportions would probably die of cold and not be able to get enough food to sustain itself.

If you were very, very small, you would feel the exact same gravity (ignoring the very tiny force due to your own gravitational mass) as if you were big. The reason why insects can pull off enormous feats of strength has nothing to do with gravity being felt differently for them. Insects pull off enormous feats of strength because all sorts of physical properties of materials are scale-dependent. For example, a piece of steel a millimeter long can supper a much larger relative weight than a 10-meter steel beam.

Insects and small creatures can pull off amazing feats of (relative) strength because of the square-cube law. Basically things like muscle and bone strength increase with cross sectional **area **(length-squared) whereas a creature’s weight increases with volume (length-cubed). So as a creature gets bigger, its weight increases far faster than its muscles and bones get stronger.

This is why small creatures can get away with such skinny bones, but large land mammals like elephants require short, stocky bones. Otherwise they’d collapse under their own weight.

Here’s an quote from On Being the Right Size

Good answers above.

I’m not sure if this helps the OP but there are creatures so small that within Earth’s atmosphere, they are weightless. Viruses, bacteria and spores float effortlessly. Various insects too.

Outside the atmosphere however, they would act the same as the bowling ball.

Video of this experiment performed elsewhere.

This isn’t true. Viruses, bacteria and spores have mass, and on Earth are subject to the acceleration of gravity and therefore do have weight, which is a force. F=mg remains true, even for these tiny things.

The difference is that the Earth’s atmosphere is moving and therefore the mass of the air under acceleration provides forces, which for tiny things like spores is greater than the force of gravity, thereby leading to lift and floating.

It’s basically the same principle as airplanes; get the air to move fast enough over the airframe, and the plane will overcome the force of gravity and lift into the air.

Very interesting paper…my only beef was how limited into examples he went for thicker folks like myself.

Upon reading everyone’s answers I could mostly extrapolate what I needed to satisfy my curiosity, but if the answer’s in front of my face I still don’t see it in terms of gravity’s effects upon a smaller mass… it was explained some by Yamatotwinkie but let the “laymen” try to reiterate… Is what’s being explained here that, say -a grasshopper can jump very far because of the proportion of it’s muscles to it’s volume and not because it’s so much lighter and gravity has less of an effect on it?

Yes, that’s why. Besides, it all matters how you do your calculations to come up with a comparison. For example, how many grasshoppers = a human? Are you going by height? Weight? Volume? Weight? Leg length? When someone’s trying to impress you by saying that an ant can lift so much more than a human, they usually use the most, uh, “flattering” number. They usually use mass, which isn’t very fair because grasshoppers are all legs, ants are all “arms”, owls are all eyes, etc. They don’t really have much in the way of brains, hearts, intestines, and such.

If you took something absolutely comparable, like length of a lever arm, the ant’s advantage goes away. If you’re lifting a grain of rice with a third-class lever where load is twice the distance as force, it’s equally difficult no matter who or what you are.

Not sure anybody has explicitly stated this, but each and every atom is being pulled toward the earth by a gravitational pull of 32feet/sec/sec. The total pull is proportional to the total mass, virus, ant, man, elephant. How fast anything falls varies with the ratio of air resistance to mass.

To help possibly clarify, the force (as the term is used technically) is much greater for a large animal/object than for a small one. That force is proportional to the mass. Size for animals roughly corresponds to mass, of course, which isn’t surprising.

That’s not really what you’re getting at, because you’re asking about the force (or ability to move against it) relative to size. It’s equivalent to saying that humans can lift hundreds of pounds but ants couldn’t possibly lift even one pound. It may help to realize that there’s a difference in generic use of “force” vs. the technical one.

Another technical details (possibly more confusing) : The force is also proportional to the acceleration an object is under. The acceleration due to gravity is considered constant in this question only because the Earth has so much more mass than the animals or objects you’re talking about. To put it another way, an ant or dinosaur are equally as effective at pulling the Earth toward them by their own gravity. (And they are both all but ineffective at that).

I think you need to understand that “gravity’s effect” and “the force on a mass due to gravity”, are two different things. The strength of the gravitational field is the same 9.81m/s^2 (=g) anywhere near the surface of the earth. The force due to gravity is equal to mass x g, so more massive objects have higher forces on them. Note that this force is often referred to as “weight”.

A grasshopper can jump (relatively) far because the ratio of its muscles cross-sectional area to its overall weight is pretty good. Scale up the grasshopper to skyscraper-size using your magic wand, and the grasshopper gets a whole lot heavier, but only moderately stronger because of the square-cube law. The muscle area to overall weight ratio is now absolutely terrible. The grasshopper can’t jump at all and promptly collapses into a large pile of goo. (This is why you don’t ever have to worry about attacks from godzilla-sized grasshoppers).

So you’re correct in that being light is one component that allows the grasshopper to jump so far, but being “light” doesn’t mean that gravity affects you any differently. Once you say that you’re light (small weight), gravitational force has already been accounted for.

Actually, no, I have never seen such a demonstration and I doubt whether many others have. There is, however, a popular myth that Galileo proved that weight is irrelevant to rate of fall by dropping objects of different weights (me did not have the concept of mass) from a high place (usually, as the story is told, from the Leaning Tower of Pisa) and observing that they all took the same amount of time to reach the ground. This story is not true. It is true that Galileo did show that (contrary to what was previously believed) weight is irrelevant to the rate of fall in a vacuum. However, he did not “prove” it through any such experimental demonstration. Nowhere in his writings or in any contemporary accounts of his doings is there any claim to have demonstrated the point in this way, and in fact Galileo probably understood that (given both the effects of air resistance on even dense objects, and the limitations of timing devices available at the time) no such experiment could have produced results clear enough to convince a skeptic. In fact, unless the experiment is “fixed” by carefully adjusting factors such as shape, surface area and smoothness, objects of different weights will not fall at the same rate in air (although, for relatively dense objects, the difference in their rate of fall may be hard to discern with the naked eye).

In fact, Galileo probably originally arrived at the insight that weight is irrelevant to speed of descent in the course of many experiments he carried out on rolling balls down inclined planes, but in his published writings, his main argument relies upon a “thought experiment” (one that is performed in the imagination, rather than actually carried out) involving two objects of different weights loosely tied together with a length of twine. Galileo is then able to show that, in this case, any theory that assumes that rate of fall is dependent on weight leads to paradoxical, contradictory predictions, and thus cannot be true.

A point about the strength of insects: You’re probably thinking, for instance, that fleas are incredible jumpers, because they can jump one or two meters up. But that’s not actually all that incredible: A housecat can also jump up one or two meters, as can a human, as can a horse. In fact, the height to which an animal can jump is largely independent of the size of the animal. The height an animal can jump to is a matter of energy: You need energy equal to your mass times the gravitational field times the height you’re jumping. And the energy comes from your muscles, and the amount of energy a muscle can put into a jump is roughly proportional to muscle mass. And the mass of a critter’s jumping muscles will typically be some proportion of the critter’s total mass. Put it all together, and the height a creature can jump is equal to some muscle efficiency factor (more or less constant) times the fraction of the creature’s mass that is jumping muscles (also more or less constant) divided by the strength of the gravitational field (constant).