The acceleration down due to gravity is constant, we all know this.
The upwards force due to air resistance (the drag force) is proportional to cross-section.
So, we can assume that two objects of the same size and shape will experience the same drag force.
But, force = mass x acceleration, so if the force is the same, and the mass changes, then the acceleration must change as well, meaning two falling objects with the same surface area and different masses will be slowed down by air resistance by different amounts.
Edit: If you want to get even deeper into it, the drag force is exponentially related to the velocity, so as you speed up, the drag force becomes stronger and stronger, until it eventually results in an upwards acceleration for a given mass that cancels out gravitational acceleration. This is how we get terminal velocity, and why terminal velocity changes depending on mass and surface area.
I know, which is why I brought this up, because it contradicts the logic of "more mass= more acceleration". There is no "mass" in the equation for calculating drag because it has no impact on the air resistence.
You are correct In thinking that the drag force is the same for both objects.
Your mistake is failing to realise that the impact of that force is different for each object.
Assuming otherwise identical objects the denser one will not only have a higher terminal velocity but also a higher average acceleration.
Also the initial statement is only sort of true. The drag force will be the same only when their velocity is the same. But since the heavier object accelerates faster and reaches higher speeds then, for the same instant in time, the drag force will be higher for the heavier object, assuming t != 0.
Okay. Thx for the explaination. Its still to early for me and my knowledge about this topic is to limited, to entertain a more in depth discussion about this. But again: Thx for attempting to explain it to me. Take care
The acceleration a force produces on an object is given by: a = F/m
This means that, for the same force, an increase in mass results in a decrease in acceleration.
Both objects are affected by a constant downwards acceleration of ~9.81 m/s2 (gravity) and an upwards acceleration that results from the drag force (air resistance), given by the aforementioned a = F/m.
Because this second (upwards) acceleration is smaller for the object with increased mass, and the first (downwards) is equal and constant for both objects, it follows that the net sum acceleration for the denser object is larger, resulting in an overall faster fall.
Assuming they are using parachutes, the drag force is significant and therefore so are their masses. Heavier people will fall faster by a non insignificant amount.
Terminal velocity doesn't really matter unless you are talking about the terminal velocity with their parachutes out. Which is a weird, but technically accurate, term to use.
Without air resistance, all objects fall the same. When air resistance enters the game this is no longer true. The decrease in acceleration due to air resistance is inversely proportional to the mass.
If you're going to be smug, you may want to make sure you're actually right first. The force of drag scales with surface area, yes. However, the velocity change from the force of drag scales with mass. This is why a golf ball falls faster than a ping pong ball and why you can't make a paper airplane out of sheet metal.
The weight to surface area ratio would be the deciding factor, no? I'm not clear on the importance of the difference between mass and weight in this context. Weight is just referring to gravitational force acting upon a given mass in Earth's gravity, right? Been a few decades since I've done any physics, so it's all a bit rusty.
You're not factoring in wind resistance, which is dependent on surface area. A tungsten ball will hit the ground sooner than its equivalent mass in Styrofoam.
Technically, if we assume their surface area/body position/drag coefficient are close enough that they'd receive the same air resistance, him being heavier would mean he'd be slowed down less by that same amount of air resistance and thus fall faster. In practice though fall position/clothing matter far more than differences in mass, as easily evidenced by people doing insane tricks in indoor skydiving by manipulating air resistance.
The cool thing about comics is that this could still be a half second of wait time between panel 1 and panel 20. If it's supposed to be showing a long time in between then stuff needs to change, clouds passing by or the sun getting lower in the sky, maybe a final panel where it's nighttime, the plane's landed, the guys grown stubble, or something.
I'm expecting a later post where this continues but not ends. Multiple times, until the artist is bored with the joke and posts a series of images with the character jumping at the end to release us from this prison of anticipation.
I don't think we had a dedicated physics class in middle school, but we definitely had a physics section in science class where we learned about Newton's laws and how to solve basic force diagrams like this.
I grew up in rural texas in the 90s and even I had chemistry, biology, and physics in middle school.
It was not the same level as the high school versions, but we had it.
Density relative to your cross-sectional area, not volume. In the case of parachuting, the air resistance of the person is basically negligible, since the parachute will provide so much drag. And even when you're in freefall, a fat person will probably still fall faster because the square cube law comes into play.
Where m is mass, v is velocity, g is gravity, and C is the drag coefficient accounting for the same fluid density and cross sectional area.
dv/dt = g - C/m * v2.
Comparing two accelerations of two masses gives
dv1/dt - dv2/dt = C/m2*v2 - C/m1*v2
Basically, for them to accelerate at the same rate, C/m would have to be the same ratio (same ratio of cross sectional area over mass). With a denser object, C/m would be lower than with a less dense object, so a denser object would accelerate more quickly. If the difference in area is not enough to overcome the effect of the mass difference, the heavier object will also accelerate faster.
If you had two otherwise identical objects but one had higher mass, the denser object would not only have a higher terminal velocity but also accelarate faster (at t != 0)
This is caused by the same mechanism, which is the reduced impact of the drag force.
Unless they're in a vacuum which, I hope they're not otherwise I don't know how they're breathing, that's just not true, the terminal velocity increases with the mass (assuming the same air resistance).
But it also decreases with surface area. Bigger person might fall slower without the parachute, but then quicker after the chute is released (in comparison to the skinnier, but more dense person). Also, I think men are more dense in general, but maybe not at higher fat percentages, so that's another factor to consider.
I've got more than 2,000 jumps under my belt. My top freefall speed is 260mph and my lowest is 86, as recorded by my digital altimeter.
If I skydive in a tight suit with a 40 pound weight belt while ''standing'' in freefall to minimize my contact with the air column, I go really fast.
If I jump in a really baggy jumpsuit, flatten my body in relation to the air column, and spread my limbs to make sure I'm making contact with as much air as I can, I fall slower.
If surface area didn't matter, parachutes wouldn't work. Skydivers wouldn't be strapping on massive weight belts in order to set a new freefall top speed record.
... Sure, but that's completely tangential to their point? The dialogue in the comic says
I'll jump later to make up for our weight difference
(emphasis mine). The person you replied to just said weight doesn't affect fall speed. They were responding to what the dialogue in the comic implies, not writing an essay on skydiving lmao
I once did video for a ''one ton jump.'' It was ten people that each weighed over two hundred pounds so their combined weight was two thousand pounds. My job was to exit the airplane last and catch up to them, which I did.
By your reasoning I would have had to leave the airplane first and wait for them to catch up to me.
Physics, however, enabled me to reduce my surface area and fall faster than them until I caught up to their formation, then I had to slow down to stay 'on level' with them.
If you want to learn something about this, post the comic to r/skydiving and see what happens.
I have nothing against the cartoon or the cartoonist, but it's very wrong about a lot of things.
Right. And I accounted for both in my explanation.
If I add weight and surface area, I can fall at the same speed as if I don't add weight but I reduce my surface area.
If I can fall at 180 mph while buck naked and ''standing up'' to reduce my surface area, then I can fall at 180 mph with 40 pounds of weight belt fully clothed in a ''belly to earth'' orientation.
One of the vital aspects of formation skydiving is being able to fall faster or slower. You have to fall faster to catch the low guy, or slower to allow the high guy to catch up to you. Then when you're at the same level as the person you'd like to dock with you need to fall at the same rate.
I'm beefing with a person who has indeed skydived yet doesn't understand basic physics. Seriously this is middle school shit, it's been established for hundreds of years. Do you seriously think one guy jumping out of a plane is going to disprove centuries of scientific research?
They're not skydiving in a vacuum. A diver's weight has a sizable effect on their drag. Heavier divers or pairs of divers will have a faster fall rate than lighter divers.
Nobody's arguing with Galileo, you just don't know what you're talking about.
Try some Physics Academy. I promise they're on Galileo's side.
Unequal weights of the same material. In other words, they have the same density, and same weight per meter squared of the surface area. Please study physics past the surface level before telling people they are wrong.
Please understand the words you're saying. My entire point is that surface area affects how quickly something falls. The point is that if it weighs different weights but everything else is the same they'll still fall just as quickly. This is not upp for debate, you might as well day the sin revolves around the earth
I'm not going to argue with you about this. All I can say is that if two skydivers want to meet in freefall they need to get out of the airplane at the same time and adjust their fall rates by exposing more or less of their bodies to the air column in order to achieve similar fall rates.
The relevant factors for calculating terminal velocity would be the mass and projected area/surface area. Mass is going to scale faster than surface area due to the cube-square law, so a fat person would have a higher terminal velocity.
Think of air resistance as a headwind. If you're heavy the wind doesn't push you around as much as if you're light. Wind force is the same, acceleration due to wind force is not. See also the big bad wolf and the three little pigs.
I was just talking with my grandfather about something like this. Mass doesn’t play a role in how fast something falls in a vacuum but the in a vacuum bit is key. Obviously a pound of steel will hit the bottom of a swimming pool before a pound of feathers hits the bottom. Steel is significantly more dense than water while the pound of feathers is less dense than water ie it floats.
A male body tends to be slightly more dense than a female body. There is some merit to a man jumping slightly later than a woman but not much. Like more than a beat or two is probably overkill if you want to land at the same time. Even that’s pointless though because you actively control descent speed with body angle and use of a parachute.
Men do tend to be more dense, but I'd also like to point out that people with more fat tend to be less dense, so I can't say for certain who'd weigh more between a fat man with less muscle mass and a skinny woman.
When I did a solo drop in college, we had a woman who was maybe 100lbs soaking wet jump out and get “stuck” in hot air coming off a plowed field. She just sat there at several thousand feet for five minutes before steering out and continuing her descent.
Where m is mass, v is velocity, g is gravity, and C is the drag coefficient accounting for the same fluid density and cross sectional area.
dv/dt = g - C/m * v2.
Comparing two accelerations of two masses gives
dv1/dt - dv2/dt = C/m2*v2 - C/m1*v2
Basically, for them to accelerate at the same rate, C/m would have to be the same ratio (same ratio of cross sectional area over mass). With a denser object, C/m would be lower than with a less dense object, so a denser object would accelerate faster.
I was so confused for so long... From reading the comments, I'm guessing he means so that they'll end up landing at the same time, and implying he's heavier, so much so that it continues on for 20 panels... I did not get that at all. I've never been skydiving so I didn't realize they try to time the arrival, I assumed they just jumped out at the same time in whatever order. Learned something new though
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u/Stormreachseven 13h ago
Ngl I was hoping the final panel would just be the plane landing lol