This one may be easier than cannibal logic

[Greg825]

No, you could theoretically throw the ball three miles into the air using only 5 pounds of force on each throw. The height does not matter for the force; only the proportion of time in the air or in your hand matters.

And to minimize the maximum (there's got to be a better way to phrase this ) force needed, all of the time spent must be used accelerating the balls upward. ie carrying them. As someone said, you're better off carrying them than juggling them, unless you can manage to utilize all of the time perfectly.

 

[BicycleTree]

Conversely, you could theoretically juggle the balls using 1 ton of force and still only have a throwing height of 1 inch. For the three mile case with 5 lb force you'd just apply the force over a long period of time, and for the 1 inch case with great force you'd just apply it over a very short period of time.

 

[Jimmy Snyder]

As I said, you would need to exert force equal to twice the weight of the ball.

If you exert a force exactly equal to the weight of the ball, then there will be no net force on the ball and it will move with constant velocity. A smidge more and it will accelerate upward.

 

[BicycleTree]

A smidge more and it will decelerate and eventually accelerate upward very, very slowly, and will spend almost all of its time in your hand. To have it spend even half the time airborne, you must provide much more than a smidge more.

 

[Jimmy Snyder]

I don't think they were unfair questions.

Now you have twisted my words.

 

[Huckleberry]

Now you have twisted my words.

Private praise and public apologies.
You are right. Rereading the thread I can see that I have made many many mistakes here. I made incorrect assumptions of Newton's laws, which you and others have been patient enough to answer.
I also made some statements that were misguided. For this I apologize to you. Early on in this thread I was set off balance by a comment directed against me. I've been having a bad time lately and was defensive even before I read that comment. I didn't even realize how poorly I misinterpeted your intentions. Here are two things I never should have said.

Just saying it is impossible according to Newton's laws doesn't explain to me why it is impossible.

I don't think they were unfair questions.

I hope that you will accept my apologies and we can go on without any hard feelings. I am sorry.

 

[whozum]

more nitpicking :) : I don't think this is (directly) so, increasing the height increases the time allowed to accelerate the ball back upward. I showed In my proof that time cancels and height is irrelavent (this was assuming the maximum amount of time was used to accelerate a ball). What really effects the force you need is the impulse you apply, which is dependant on time spent accelerating the balls upward.

Thats pretty much exactly what I said, The force you need to apply must be greater than the impulse of the ball's impact and the impulse to get rid of it again.

I'm looking for your proof now though.

edit:

increasing the height increases the time allowed to accelerate the ball back upward.

I don't tihnk this is so at all. Regardless of how high the person threw it, assuming it is not along the magnitude of his maximum throw ability, that he can maintain the same contact time with the ball regardless of how high it comes down on him. Howver, your and my experiments are under different premises.

My statement says that to reach the original height of the preceding throw one must apply an impulse with twice the magnitude of the ball as it hits his hand. How long it takes him to do this doesn't really matter until you start considering time constraints of the other balls, which I didnt. I merely simplified the juggle so Huckleberry could see that it takes more force to catch and throw something than it does to just hold it.

 

[Jimmy Snyder]

I have some apologies to make too.

To Huckleberry, I wrote the 'twisted' post without having read an earlier post of yours in which you had already said you understood the reason juggling fails. In any event some of my responses to you were born of impatience.

To Greg825 and BicycleTree, In my post #34, I thought I had explained things rather well, but in rereading, I see that I did not make it clear. I meant that you would have to exert a force equal to twice the weight of the ball, just as BicycleTree said. One unit of weight to support the weight of the ball and one unit to reverse the velocity. I think Greg825's post #35 missed that point (quite understandably so) and my posts on the subject after that point are incoherent.

 

[Greg825]

Thats pretty much exactly what I said, The force you need to apply must be greater than the impulse of the ball's impact and the impulse to get rid of it again.

I think the fault may be mine here, I didn't really understand what you were saying in most of your post when I responded, I was only refuting that first statement.

I don't tihnk this is so at all. Regardless of how high the person threw it, assuming it is not along the magnitude of his maximum throw ability, that he can maintain the same contact time with the ball regardless of how high it comes down on him. Howver, your and my experiments are under different premises.

My statement about more time allowed was based on the two premises that the force applied would be constant and this force is desired to be minimal.



I'm also unsure of what you mean by "I don't tihnk this is so at all. Regardless of how high the person threw it, assuming it is not along the magnitude of his maximum throw ability, that he can maintain the same contact time with the ball regardless of how high it comes down on him.", my saying he is allowed more time to accelerate it upward doesn't conflict with the fact that he can also not use more time if he doesn't want to. Neither of these statements are contradictory as they are simply two proposed possibilities. Can you please clarify?

 

[whozum]

I was just pointing out that they arent necessarily requirements, just possibilities. I was oging for constant time, you were going for constant force.

 

[ArielGenesis]

if the bridge is vertical, i could just jump with the ball and the mullet. it doesn't matter much wether i DO survive right.