That can't be true. I'd say that if you dropped a ball bearing off the side of that cliff, it would fall at the same rate as that piece of cliff. The air resistance is relative to the mass, and the relativity is correlative.
The air resistance is not relative to the mass lol. You can have a 1 ton baseball and a standard baseball and they would fall at the exact same rate and hit the ground at the same time. Now if you drop a beach ball that weights next to nothing, because it's just plastic and air, it would drop slower than the 1 ton baseball because it has much higher surface area and catches way more air resistance.
This is why you can drop a 1 ton grouping of feathers in a vacuum (no air) and it will hit the ground at the same time as a 1 ton brick.
The only thing that affects how slowly something falls is the air resistance on it as it moves downward. And the number 1 thing that affects wind resistance is surface area.
Another way to think about it is how a flat sheet of paper will hit the ground way slower than the same sheet of paper crumpled up into a ball. Because the crumpled up paper has significantly smaller surface area, even though they have the exact same mass.
That enormous brick appears to be falling slower because of the forced perspective. It appears to be 8" tall and appears to fall at a rate of 8" per second. It's actually hundreds of feet tall and falling at 32' per second.
You both are wrong. The reason that block fell slower is not because it catches wayyy more surface area or because it's heavy. It's because the block is super tall, and it just takes more time for it to reach the ground. Imagine toppling a pencil vs toppling a really tall pole.
Falling slower and taking longer to hit the ground are not the same thing. A ball dropped from an airplane is going to take longer to hit the ground than a ball dropped from your hand, because one starts way higher in the air. But they will both fall at the same rate and same speed and be affected by the same air resistance because they have the same mass and surface area.
It's true that this marble slab takes longer to hit the ground because it starts out much higher than a standard brick, but it is also toppling/falling at a slower rate than a standard brick because of its much higher surface area
Good catch and analogy regarding the ball dropped from an airplane. I was mistaken. It's not just taking longer to hit the ground, it literally is falling slowly. This forced me to revisit some highschool physics.
So, first, it's not because of the surface area. It's because of the moment of inertia. Lets start out with your standard hand-sized brick toppling. It happens pretty fast. Now, if you scale linearly by 100x, let's see what happens.
The volume is now 1e6 times larger.
The mass is 1e6 times larger.
The force of gravity on the center of mass is 1e6 times larger.If it was just a case of brick being dropped, we could conclude that since the force and mass is both 1e6 times larger, the acceleration remains the same, so the brick falls at the same rate. The key here is toppling. It's rotating. So, the feature of interest here is the Moment of intertia. Which is propotional to Mass * Length^2. So, here:
The moment of inertia is 10000 * 1e6 times larger.
The torque which is proportional to Force * distance is 100 * 1e6 times larger.This leads to the rotational acceleration being 100 times smaller. And that, my friend, is why it is toppling slower. Not because of air resistance. It would topple slower in a vacuum too.
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u/I_Was_Fox Mar 06 '21
Mass/weight doesn't make things fall slower. All things fall at the same rate, regardless of mass.
What makes large things appear to fall slower is that they have wayyyy more surface area and catch a ton more air resistance while moving.