tromak
Bogey Member
so that settles it then...?
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How fast (in mph) do discs travel?
- Thread starter jchoate7
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tromak
Bogey Member
well actually a bullet does continue to speed up after it leaves the barrel of a gun. you can check detailed ballistics charts for that. We all know when you let off the gas of a car your not done speeding up. go try it. also if there are any baristas on here that can back me up on the steamed milk thing that would be great. I know the milk doesn't make much sense but its just a different example of energy being applied to something, and on a molecular level more energy is faster movement. These arent't the same thing as a disc though. for a disc you might be right. but those three things are true.
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The bullet doesn't speed up after the force is done being applied to it, the gases coming out of the muzzle and the exploding gunpowder continue to propel it after leaving the barrel but as soon as that stops pushing on the bullet it begins slowing down. Your car definitely does not continue speeding up if you're on flat ground and you stop giving it gas. The milk right at the point where the heat is applied does not heat up, but the rest of the milk heats up (and that point cools down) as the heat propagates throughout the liquid. The overall amount of energy in the milk and it's container certainly doesn't continue to increase after heat is no longer applied. It's all about when the energy stops being applied to the system, with a disc golf throw that happens when you're no longer in contact with the disc.
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Only shows one chart, unable to scroll to find subsequent charts in that link, but if I could, I suspect I would find some sort of misinterpretation or something out of order.
^Believe in him, for he speaketh the truth. Do not be lead down the road of temptation that sayeth: "Thine disc will continue to accelerate after it has left thine hand." This is simply a ploy by the Devil to lead you astray! Take a physics class, and understand the way the world that has been created for you actually works - it really is amazing stuff.
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I've worked at Chrysler, now at Ford. I have numerious friends who would love to see this demonstrated. If you could show them what it is they've been missing, they can make you a wealthy man.
You must be thinking about those Toyotas where the gas pedal got stuck. I see how those could accelerate after you let up on the gas- but only because additional energy (fuel) was still being applied to the system. I'm not bashing Japan, and touting US here. I'm trying to explain that you need to apply force to a mass to accelerate it. You need to apply provide aditional energy to an object to increase its kinetic energy. These aren't theories or opinions, they are facts.
I'll buy the bit about bullets continue to accelerate after leaving the barrel... momentarily, because the gasses propeling them continue to expand (i.e. they are doing work on the system). Once they are no longer able to act on the bullet, it starts slowing down.
Remove your foot from the pedal, and the engine stops providing enough force to accelerate a moving car. Once the disc leaves the hand, it starts slowing down, because as Mash pointed out: energy is no longer being applied to it.
Strictly speaking: after you let your foot off the pedal the car does accelerate - negatively. Without the application of sufficient force to overcome the wind resistance at a given speed, the car/disc will slow down. In terms of math/physics, this would be negative acceleration in the direction of motion, commonly referred to a deceleration.
I wonder if this is the source of the confusion? Regardless what you call it, without additional energy and/or force in the direction of motion, the object is slowing down due to friction. All objects (not in a vaccum) all the time; bullets, cars, discs, baseballs, arrows, even magic fairies slow down when they stop beating their wings.
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Lurp Nuts
* Ace Member *
i'm glad we have guys like BogeyNoMore and Mashnut on here to write up coherent responses. mine would just end up too short, and sounding like "you're an idot."
Angular acceleration continues to have an impact on the velocity of the disc after it is released from the fingers. As a result, the disc will continue to have linear acceleration for approximately 1 second after it is released from the finger tips.
Some of you are saying that it goes against the laws of physics. If the disc was released with no spin, then you would be correct. However, as the rear of the disc rotates around your pinch point, angular acceleration is created and acts as a force after the disc is released.
This is the whole theory behind Blake's secret technique on discgolfreview.com. He has said repeatedly that if your timing is right, you can make the disc move faster than your hand was ever moving.
Some of you are saying that it goes against the laws of physics. If the disc was released with no spin, then you would be correct. However, as the rear of the disc rotates around your pinch point, angular acceleration is created and acts as a force after the disc is released.
This is the whole theory behind Blake's secret technique on discgolfreview.com. He has said repeatedly that if your timing is right, you can make the disc move faster than your hand was ever moving.
I think you misunderstood Blake's point, it's certainly possible by taking advantage of all possible levers in the throwing motion to get the disc moving faster than you could swing your hand, that's just using simple mechanical advantages. I'm skeptical of the idea of the rotation of a disc increasing it's linear velocity, one part of a solid object can't impart force on another part of the disc without an equal and opposite force acting on that part of the disc, it all moves as a unit.
Its okay to be skeptical, just do some more research before you dismiss the idea. The mechanical advantages that you referenced are exactly what creates angular acceleration. If the disc is moving faster than the hand, there has to be a second force acting on the disc that causes the increased velocity.
On another note, compression is the reason that a bullet continues to accelerate after the hammer makes impact with the bullet. The compressed air will continue to push the bullet just past the tip of the gun.
On another note, compression is the reason that a bullet continues to accelerate after the hammer makes impact with the bullet. The compressed air will continue to push the bullet just past the tip of the gun.
a disc would totally accelerate after my release if i threw it with less than 9.8 m/s force. off a big cliff.
[gravity reference: 9.81 meters/sec, or 32.2 feet/sec, or 22 mph.]
QUESTION:
if i threw a disc with the usual force i generate, i'm imagining the velocity forward would decelerate in an exponential way at release. like, a predictable curve down to 0 speed on the ground or y axis or whatever.
how does gravity impact my throw? especially if i lowered the ground, or y-axis, giving gravity more time to affect the throw?
there's a rule of thumb goin round that 3ft distance = 1ft change in elevation / y-axis. but i can't wrap my mind around gravity affecting deceleration in such a linear way. halp.
[gravity reference: 9.81 meters/sec, or 32.2 feet/sec, or 22 mph.]
QUESTION:
if i threw a disc with the usual force i generate, i'm imagining the velocity forward would decelerate in an exponential way at release. like, a predictable curve down to 0 speed on the ground or y axis or whatever.
how does gravity impact my throw? especially if i lowered the ground, or y-axis, giving gravity more time to affect the throw?
there's a rule of thumb goin round that 3ft distance = 1ft change in elevation / y-axis. but i can't wrap my mind around gravity affecting deceleration in such a linear way. halp.
texhop58
Eagle Member
I would like to see espn do this with their sport science segment they do from time to time. It would be interesting
tromak
Bogey Member
First of all props to everyone for being civilized in a topic that obviously everyone doesn't agree on. so i have a manual transmission car. i just took it out and accelerated to 45 miles per hour as fast as i could. At 45 i let off the gas and at the same time i pushed the clutch in to insure that no power was being recieved from the engine. I for sure continued to speed up a good 5-8 mph before i stopped speeding up. This obviously isn't done in a lab Im sure that there was latent power being applied to the wheels but i did it enough times i just still feel like were all missing something here. And yeah i know why a bullet continues to speed up and i know why the milk continues heats up. thats exactly my point to just say without taking into account all variables that the disc stops speeding up once it leaves the hand isn't really the right way to go about things. A lot of people dont know how its possible for a sailboat to sail faster than the wind but it still happens. Theres a lot of similarities between what makes a disc fly and what pushes a sailboat. So thank you guys for sparking my interest and were just going to have to agree to disagree on this one. I do agree in most cases the disc does immediately start slowing down but not in all cases. downhill,crosswind,quartering wind. obviously applying newtons laws of motion debunk my inertia theory but what about all the other variables?
http://youtu.be/k7u8m0Qpn38?t=1m33s
here's a helicopter that loses power (force?) way up high then falls safely to the ground.
It 'autorotates' -- like this helicopter plant falling:
or like a spinning disc(?).
My understanding of autorotation is that a spinning thing generates its own force (lift?) by harnessing the force of downward velocity (ie gravity) for itself. The video shows a force-less but spinning helicopter (disc) can create upward velocity before it lands.
On one hand, it seems like this spinning action supports the idea that discs can potentially generate their own force (lift) after the release point.
On the other hand, the spin just decelerates(?) a greater force (gravity) before it lands, and doesn't actually create more force than its power provided before it gets cut off (the release).
(sorry if this is getting too tangential :wall:. anybody's welcome to PM me that wants to help me understand this stuff! )
here's a helicopter that loses power (force?) way up high then falls safely to the ground.
It 'autorotates' -- like this helicopter plant falling:
or like a spinning disc(?).
My understanding of autorotation is that a spinning thing generates its own force (lift?) by harnessing the force of downward velocity (ie gravity) for itself. The video shows a force-less but spinning helicopter (disc) can create upward velocity before it lands.
On one hand, it seems like this spinning action supports the idea that discs can potentially generate their own force (lift) after the release point.
On the other hand, the spin just decelerates(?) a greater force (gravity) before it lands, and doesn't actually create more force than its power provided before it gets cut off (the release).
(sorry if this is getting too tangential :wall:. anybody's welcome to PM me that wants to help me understand this stuff! )
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First of all: This applies to and an object in freefall. Yes, they accelerate at 9.81 m/s/s towards the groud. If you want to play by "dropping" your discs (with no spin), be my guest... let me know how many shot it takes to hole out.
When you throw a disc, the lift creates glide, so it doesn't fall at 9.81 m/s^2. That's how come they travel farther than say, a baseball... they travel farther because they stay aloft longer due to their aerodynamics, not because we can throw them faster (because we can't).
2nd of all, we're discussing acceleration along the direction of motion, not toward the ground. Gravity plays no role in accelerating your disc down the fairway unless you're throwing downward, and I've already discussed in this thread how that force is counteracted by wind resistance, which increases disproportionately to the velocity.
At this point, I'm done disputing people who think somehow, a disc can go faster once they let go of it. It's not in freefall, and it doesn't have expanding gasses propelling it. People have drawin inconsistent analogies attempting to refute proper application of classical Newtonian Mechanics. If I haven't convinced you by now, I believe I lack an approach that will be successful.
My technique seems to have plateaued at the point where the fastest my discs will ever go is at the moment of release. I can only marvel at those who somehow get their discs to increase their kinetic energy and linear velocity after they release - I am in awe of each of you.
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All hail the Master Accelerator! May his power be ever mysterious and unfathomable!:wall:
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No wonder Discraft named a one of their fastest discs the Force.
notroman
* Ace Member *
That's why I never even bothered getting into that debate. Once I saw that reply to my post I was like "I'm not touching this". I did get a lot of laughs at some of the replies here though. :clap:
theeterrbear
Par Member
Deja vu... one of the first threads I ever read on this forum was like this. And I swear the joke about the Force was there. And the Master Accelerator thing.
And Bogey, I think I know a way to convince them. Percussive maintenance. :doh:
Please read and study the graphs on page 747 of the linked study on frisbee flight and dynamics.
http://www.lpl.arizona.edu/~rlorenz/frisbee_mst.pdf
The graph labeled Frisbee Launch Acceleration indicates a positive radial acceleration for up to .4 seconds after release. How can there be radial acceleration if the fingers are no longer applying force to the disc?
Since the total kinetic energy of a moving disc is the sum of its linear kinetic energy and rotational kinetic energy, wouldn't an increase in angular velocity also increase the total kinetic energy during that brief .4 second period?
I know that the disc isn't going to accelerate 100 feet down the fairway. I am referring to a very brief moment of acceleration after the disc leaves the hand due to increasing and shifting kinetic energy.
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