Karadan on August 10, 2009, 08:25:43 pm
I've always considered "escape velocity" to be a misnomer, and not because it's actually a speed instead of a velocity.

I am sensing what we lawyers call "a distinction without a difference." So I'll bite, my dictionary defines both speed and velocity as "distance traveled per unit time." Am I missing something here?

He is saying that he -isn't- talking about speed vs velocity (there are slight differences in physics), but by the fact that any speed moving away from an object with gravity will eventually get out of it's gravitaional field, it could just take a while.  He is saying it "should" be called "Escape Kinetic Energy".

And very true, 120 kph vs 200 kph, your still fairly screwed either way.  But you throw in body armor possibly absorbing some small part of the impact, his adjuster gun decreasing that by a few more KPH, and the fact that even a fall from a plane can occasionally be survived, and the kind of quick response and high grade medical treatment he could be receiving, and there is a very notable chance, especially if the plot line requires him to survive. :)
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As for the max falling speed, think of it like this:  You stop accelerating when forces in opposite directions are equal right?  Like if you press your hands together, even though both have lots of force, neither are going anywhere.

So, since force is measure in newtons which is (kg * m)/s^2 or mass x acceleration, the downward force is based on mass and gravity (which is where we get weight from, and why you weigh different amounts on earth, the moon, and in space).  Now, the upward force is going to be based on air resistance.  No fancy formulas here, but I think we can agree that as speed goes up, air resistance goes up, thus a higher amount of force.

So, lower gravity = lower downward force.  Lower downward force = less upward force in order to have no net acceleration.  Less upward force = less air resistance.  Less air resistance = lower falling speed to achieve the air resistance needed.  Lower falling speed = lower falling speed = lower terminal velocity.

Hope that made sense.  We may learn rather soon if he survived or not though, as the medics will likely call the big man himself and say 'Yep, he's dead Jim' or 'Wow, he actually survived that.'

Azure Priest on August 10, 2009, 09:00:43 pm
The technical difference between Speed and Velocity is that velocity has a directional component, speed does not. For example, the SPEED of light does not change, but the Velocity does when light's reflected, refracted, or in any other way is made to change direction.

None of that applies to the current discussion, however, except for the Kinetic energy being 1/2 m(ass)* V(elocity)^2.

If our "professional" skips the surface like a stone, he will have a much lower velocity (delta v), than if he hits head on. Considering his angle of descent, unfortunately, the latter is far more likely meaning his suit and body will take most if not all of the Kinetic energy of impact. As opposed to having the Kinetic energy "burned" away by friction. It's like the difference between sliding to home plate and running head first into a flagpole.
« Last Edit: August 10, 2009, 09:02:33 pm by Azure Priest »

Bungalow_Bill on August 10, 2009, 10:43:15 pm
Speaking of physics, how about the sound propagation in that atmosphere? If it's anything like Earth normal, the boy must have one hell of a set of lungs in him. I mean, if that little dot is him, he's a good mile or more away and they can still hear him just fine from inside a sealed environment suit:D

Karadan on August 11, 2009, 07:57:27 am
Speaking of physics, how about the sound propagation in that atmosphere? If it's anything like Earth normal, the boy must have one hell of a set of lungs in him. I mean, if that little dot is him, he's a good mile or more away and they can still hear him just fine from inside a sealed environment suit:D

Hmm, good point.  I kinda figured that sound was from something besides him shouting, or that it was simply showing that he was shouting, not that they could hear him.  Just because we 'hear' him from a place where the 'camera' is, doesn't mean that characters near the 'camera' can hear him as well.

My first thought was that it was the sound of his adjuster gun kicked up to max and firing strait down, mostly because you don't see people shouting represented by 'EEEE' generally, usually more of an 'AHHH'.  Or it could have been trying to represent the whistling sound that bombs and Wile E Coyote are famous for.

Edit: Actually, looking back, it certainly does seem as though they can hear him because Bert and Erny are looking around unable to find him, then suddenly can find him seemingly thanks to the sound.

Also, it seems that they do mention the escape velocity as being somehow mentioned as being related to terminal velocity, though I've never seen that before in my years of physics classes.  I'm sure there is some way to relate the two, but they don't seem directly related.  Anyway, the big man himself says 200 kph, but I believe that is a mistake on the part of the author, despite what a good job he did with gravity in general on TLP.
« Last Edit: August 11, 2009, 08:05:21 am by Karadan »

SandySandfort on August 11, 2009, 12:10:13 pm
Hmm, good point.  I kinda figured that sound was from something besides him shouting...

That is correct. He is aerodynamically very "dirty." He has his thruster device, his rifle, etc. So yeah, Wile E Coyote sound effects from his passage through the air. Speaking of the thruster device. It's thrust is pretty insignificant. It is like similar devices the astronauts use to move about in zero g. It is useful only in a zero or micro-gravity environment. It's useless on TLP.

I'm sure there is some way to relate the two (escape velocity and terminal velocity), but they don't seem directly related.  Anyway, the big man himself says 200 kph, but I believe that is a mistake on the part of the author, despite what a good job he did with gravity in general on TLP.

I think it is indisputable that escape velocity represents the fastest speed a freely falling object can attain before impacting a body. Thus, terminal velocity must always have escape velocity as an upper limit.

With regard to 200 kph, vs. 120 kph, Tobi... yeah Tobi, got it wrong. I will defer to your numbers. And just to get past the idea that our bad guy survived, let's just say he hit head first, against solid rock, at 120 kph. Brain soup. Okay?

J Thomas on August 11, 2009, 03:00:43 pm
Quote
I think it is indisputable that escape velocity represents the fastest speed a freely falling object can attain before impacting a body. Thus, terminal velocity must always have escape velocity as an upper limit.

Yes, if by freely falling you mean it starts out its fall at rest and doesn't get new velocity from anything but falling.

Since the gravitational force decreases with the square of the distance as everyone has agreed, he would fall slowly at first and gradually build up speed. And the air resistance is small while the speed is slow. Without working out the numbers I would consider the possibility that he doesn't build up to terminal velocity in the time he has to fall. He could still be going slower. That is, he could still be accelerating when he hits, never getting to the speed that air resistance cancels his acceleration. Or maybe the numbers would show that he does reach terminal velocity, I don't know.

For the plot, all that's important is that his brain is mushed, and that can sometimes happen on earth from a fall of ten feet or less. So there aren't any gotchas here, only yes-buts.

Suna Amlin on August 11, 2009, 11:36:06 pm
I was under the impression that this isn't really a planet and at the core is a teeny-tiny black hole...

The black hole draws like gravity but has limits of reach based on it's size which would reflect in a stronger pull as distance shrinks...   

*shrug*  just a thought ....

SandySandfort on August 12, 2009, 07:41:21 am
I was under the impression that this isn't really a planet and at the core is a teeny-tiny black hole...

"Planet," as we have seen of late, is a rather arbitrary designation. TLP is small but massive, thus it is round due to gravity. I guess under the current IAU definition it would be a dwarf planet.

The black hole draws like gravity but has limits of reach based on it's size which would reflect in a stronger pull as distance shrinks... 

The mass of the black hole and the rest of TLP generate gravity just like any other body. The strength of TLP's gravitational pull, varies as to the inverse of the square of the distance. The question that may have you confused is, "distance from what?" The answer is almost always, "from the center of gravity." (I think there may be special cases for non-spherical shapes such as toruses, but for any generally round body, the center of gravity is treated as a point source.)

quadibloc on August 16, 2009, 09:00:05 am
I just realized, as I was looking for another item, and so looking back through earlier stips, that there was a tip-off about this. The assassin mused that it was odd that there was no gravity at all, instead of a little gravity, at his distance from Tobi's asteroid. Thus, there could have been any amount of gravity there - he failed to recognize that when in orbit, one is in free fall. So that tells us he didn't check his orbital characteristics to find out what the asteroid's mass was.

I haven't quite paid the same level of detailed attention to this webcomic as I do to Girl Genius.

Azure Priest on August 19, 2009, 11:10:48 pm
well if not "brain soup"ed, then lobster boiled. The entry angle with the most chance of impact survival ALSO generates the most heat from friction. There's also "chest tererium", "spine impalement", "boulder kiss" and all other rather ghastly forms of death from impact. Considering his last close-up, I'm going with "chest tererium" where his ribs break free of the rib cage and pierce his internal organs.

Brian on August 22, 2009, 03:39:03 am
I want to front-load my comment about the physics in the comic by stating I'm a Ph.D student studying physics and have a B.S. in physics/astro and a minor in math.

You do a damn good job on the physics.  I'm impressed.  Any occasional 'oops' is trumped by the great story and overall feeling of the comic.

Keep up the good work.

Karadan on August 24, 2009, 07:36:11 pm
TLP is small but massive

I love it when people know the definitions of words.

That would make a great shirt.  The letters TLP around the top of a picture of TLP, with the words 'small but massive' underneath.

SandySandfort on August 25, 2009, 01:37:56 pm
I want to front-load my comment about the physics in the comic by stating I'm a Ph.D student studying physics and have a B.S. in physics/astro and a minor in math.

If you don't mind, I would like to tap you for future physics issues. Please send me your e-mail in a private message.

You do a damn good job on the physics.  I'm impressed.  Any occasional 'oops' is trumped by the great story and overall feeling of the comic.

We try to get it right. Thank you for your kind words. Feel free to call oopses to attention. We need all the help we can get.

Lee A. on August 28, 2009, 04:10:33 pm
#1. It's science Fiction. In Science Fiction things can happen any way the author chooses. It doesn't have to make sense.
#2. It's a comic.  It's a funny book. nothing to get all excited about. It's not life changing you know. (If it is for you, seek help.)
#3. The writer and artists can do it any way they please. It's their work. It's their art. It's their idea.  Questions?  See #1, and #2.

Sean Roach on August 28, 2009, 11:15:32 pm
Nitpick.
#1, it's science fiction.  In fantasy the author can get away with whatever.
Fortunately, our authors are good about staying within what might be.
#2, it's political, and deliberately so.  The idea IS to change your way of thinking, which pretty much does change your life.  Still, it's a fun read, or else no one would bother.
#3, still valid.