How fast (in mph) do discs travel?

[jchoate7]

Tromak this is a guess (as I'm no physicist) but on earth as soon as you stop apply force to an object opposite forces such as wind resistance will immediately start to deaccelerate whatever the object is. In space (vacuum) there is nothing to deaccelerate an object so the object will continue accelerating? Just a guess I'm really talking out of my caboose right now lol.

 

[A rod]

I thought good drive form was to get it so you're still accelerating through the release. It might slightly speed up ourt of the hand but a very small amount. Then the air/gravity acting on it will start slowing it down

 

[BogeyNoMore]

I think i disagree with the top statement. A disc doesnt immediately start slowing down. yes - it does.
I think it is still accelerating for a little ways out of your hand. no - it doesn't

These statements are contary to the most fundamental principles of physics, and could only be made by someone who's never taken a HS physics class. Even with a tailwind, a thrown disc is going its fastest the moment you release it, and starts slowing immediately. It may still have decent velocity 10' or 100' down the fairway, but it's going slower than it was off the tee, and slows down more the fartest - and not at a constant rate, either.

Also, this is what Innova used to imply their speed rating is: disc's ability to retain it's initial velocity, but I digress.

 

[ohtobediscing]

Tromak this is a guess (as I'm no physicist) but on earth as soon as you stop apply force to an object opposite forces such as wind resistance will immediately start to deaccelerate whatever the object is. In space (vacuum) there is nothing to deaccelerate an object so the object will continue accelerating? Just a guess I'm really talking out of my caboose right now lol.

You're talking out of every orifice you've got.:|
In a vacuum, an object's speed could stay contant, if not for A)impacting space dust[yes] which slows the object in infinitesimal amounts, and B) the gravitational push/pull of large celestial objects it might pass, which may cause the object to accelerate or decelerate.

Nothing is constant but change. Om.

 

[jchoate7]

You're talking out of every orifice you've got.:|

Oh, I know lol. I'm just really bored at work right now.

 

[theeterrbear]

These statements are contary to the most fundamental principles of physics, and could only be made by someone who's never taken a HS physics class. Even with a tailwind, a thrown disc is going its fastest the moment you release it, and starts slowing immediately. It may still have decent velocity 10' or 100' down the fairway, but it's going slower than it was off the tee, and slows down more the fartest - and not at a constant rate, either.

You are correct. The exact moment just after the energy is finished being transferred to the disc is the greatest amount of energy the disc will have (unless thrown in a manner to take advantage of the potential gravitational energy of the disc). Any time after the disc is released it is losing energy to the air, and eventually the ground.

And regarding the spin of OH and FH throws (I thought of this while typing the earlier paragraph, that is why no multi-quote): the more spin a disc has, the more difficult it will be to get the disc to deviate from it's axis of rotation due to angular momentum. If you have a wheel with an evenly weighted rim and handle bars that are the rotational axis you can test this for yourself. The faster the wheel is spinning, the harder it will be to move the wheel off of this axis. It's a neat little trick commonly used as an introduction into this branch of Newtonian mechanics.

Also, I believe a lot of the confusion was made with inertia. Newton's first law is that an object at rest with no outside forces acting upon it will remain at rest and an object in motion will maintain its motion until acted upon by an outside force. Accelerations are caused by forces divided by the mass of the object, a=F/m --> F=ma, which is normally how it is presented.

Disclaimer: I'm a little foggy on the specifics of everything, but this should be largely correct.

 

[theeterrbear]

In a vacuum, an object's speed could stay contant,

Technically, it is the velocity that would remain the constant. Speed and velocity are similar concepts, but a velocity vector has a direction (and thus all velocities have directions) and speed does not include direction. This is very important when it comes to momentum, as it is momentum that keeps the object headed in a certain direction. If we were just talking about speed, the object could be zig-zagging in any direction.

 

[mashnut]

Well a bullet continues to accelerate after it has left the barrel of a gun. A car continues to accerlate after you let off the gas. Milk continues to heat up after you turn the steam off. Dont quote me on this but i believe newtons laws of motion tell us that an object will continue to accelerate even after an applied force has been taken away. Im not sure if it was newton that proved it but it doesnt matter we can see this phenomena in our everyday lives and it definatly applies to a disc.

Ok i just checked myself and i may have spoken to soon. it looks like im wrong i guess. I think that may only apply in a vaccum. I remember being taught something like what i said and i know that the three examples i gave are true. i just cant find the law of physics that backs me up. Im still not convinced but i guess we need a physicist to chime in on this topic.

None of those are true. Velocity remains the same unless acted on by an outside force, acceleration is due to an outside force. As soon as a disc leaves your hand it stops accelerating due to the force you apply and is acted on by things like wind resistance and gravity which serve to slow it down.

 

[BogeyNoMore]

@theeterbear - Actually, you don't seem too fuzzy about your facts (somewhere, a physics teacher is smiling). As for gravity's affect on the disc's velocity:

Assuming we throw a disc down hill, as we do during play , (rather than dropping the disc like any object in a pysics free fall problem), I don't think the disc ever experiences any net postive acceleration due to gravity. Don't get me wrong: gravity affects the disc, but I doubt that force is enough to overcome wind resistance, which it would have to be in order to create any acceleration after the disc leaves the hand. I think it serves to negate some of the effect of wind resistance (i.e. the rate of decelleration due to resistance is lower, specifically due to gravitational accelertion). The only place I can possibly see any disc accelerating after it leaves the hand would be when the gravitational accelertion > than the opposing wind resistance.
Since wind resistance is proportional to the square of the velocity, this could only happen when v is relatively low ( i.e. the end of the flight.
But years of observation tell me even discs thrown downhill don't don't accelerate towards the end of their flight. Not sure at what angle of decline you would have to throw for gravity's pull on the disc to exceed the wind resistance, (but I'd hazard a guess it's 45°), but eventuall, it would accelerate to the point where wind resistance > gravitational acceleration (i.e. terminal velocity).

Technically, it is the velocity that would remain the constant. Speed and velocity are similar concepts, but a velocity vector has a direction (and thus all velocities have directions) and speed does not include direction. This is very important when it comes to momentum, as it is momentum that keeps the object headed in a certain direction. If we were just talking about speed, the object could be zig-zagging in any direction.

while you are 100% correct(i.e. velocity is a vector, speed is a scalar) we may have to allow people to use the more common term speed in place of velocity for purposes of everyone undertanding the concepts.

 

[DeadEye]

If you were throwing downhill, in a stiff tailwind, with late acceleration and lots of snap... you might get some acceleration after the release.

 

[OpposableThumbs]

This became an incredibly entertaining dissertation on physics and how it relates to a disc's flight with a dash of MLB player comparisons and other assorted laughs. Good stuff all around :clap:

It's kinda like as soon as you're born, you begin to die.

I lol'd!

Technically, it is the velocity that would remain the constant. Speed and velocity are similar concepts, but a velocity vector has a direction (and thus all velocities have directions) and speed does not include direction. This is very important when it comes to momentum, as it is momentum that keeps the object headed in a certain direction. If we were just talking about speed, the object could be zig-zagging in any direction.

@theeterbear - Actually, you don't seem too fuzzy about your facts (somewhere, a physics teacher is smiling). As for gravity's affect on the disc's velocity:...
...while you are 100% correct(i.e. velocity is a vector, speed is a scalar) we may have to allow people to use the more common term speed in place of velocity for purposes of everyone undertanding the concepts.

I lol'd again.. but love the hard-line approach from theeterbear here, don't cut the lay-people of DGCR any slack on semantics! :thmbup: One wouldn't dumb it down if this were a discussion about disc X's flight path or what have you..

Is it possible however, that for a few milliseconds after release, the disc does continue to accelerate, but only for a fraction of a second?

 

[BogeyNoMore]

Is it possible however, that for a few milliseconds after release, the disc does continue to accelerate, but only for a fraction of a second?

Not without an outside force. YOU are supplying the force. When it leaves your hand, all that's left are:

-gravity
-wind resistance (and other more complex) aerodyamic forces that dealing with lift and turn, etc
-precession
none of which are acting with a net force in the direction the disc is travelling.

Wind resistance is the primary reason the disc's velocity slows, and it is greatest when velocity is highest (i.e. when it leaves your hand). The disc will never decellerate faster than it does the first moments of its flight (assuming the wind doesn't change).

There' s quite a bit of fundamental misinformation in some of the posts in this thread. While interesting, this isn't one of DGCR's better disc physics threads (there are quite a few).

 

[BogeyNoMore]

There' s quite a bit of fundamental misinformation in some of the posts in this thread. While interesting, this isn't one of DGCR's better disc physics threads (there are quite a few).

Maybe that was a bit harsh: the misinformation was from people asking, or clearly stating opinions.
The incorrect statements weren't necessarily presented as fact.

 

[OpposableThumbs]

Gotcha. Can't argue with Newton and co.! I was thinking (incorrectly ) it was possible that the moment immediately after energy was transferred from your body into the disc, the.. drag/resistance?.. that your hand imparts on the disc leaves the disc, and so the top speed is effectively achieved at the 'moment' of release, but this 'moment' occurs when the disc has already flown say a centimeter or so.. Sorry to contribute to the misinformation! lol.. this was a totally random thought, coming from a very limited knowledge base, so I accept that I'm wrong and will move on!

Thanks for the clarification!

 

[BogeyNoMore]

^ It's all good. Obviously, I enjoy these threads

 

[Star Shark]

Are we talking African or European discs?

 

[hiflyer]

Are we talking African or European discs?

well. I don't know that.. aaaaauuuuuggghhhhh!!!!!!

anyway, everything is pretty much accelerating at all times. positive or negative, anytime anything experiences change in direction, velociy, or (more vaguely) speed, it has accelerated.

 

[Jeasy13]

Some of these responses make me cringe. I'll dumb it down and quote my 6th grade science teacher for those of you that have either forgotten, failed, or never taken a physics class.

" Think of it like riding a bicycle on flat ground. As soon as you stop pedaling, what happens?"

Entire class of 11 and 12 year olds response : "You slow down!"

 

[BogeyNoMore]

Some of these responses make me cringe. I'll dumb it down and quote my 6th grade science teacher for those of you that have either forgotten, failed, or never taken a physics class.

" Think of it like riding a bicycle on flat ground. As soon as you stop pedaling, what happens?"

Entire class of 11 and 12 year olds response : "You slow down!"

lulz

 

[Mocheez]

Don't be so arrogant. A disc will accelerate briefly coming out of the hand due to angular accelaration. See the 4th chart down on the attached link... http://burkphysics.com/wordpress/whitw/files/2011/10/Tennis-Ball-Vertical.png