Your Day

The Batlord · 08-24-2019, 08:50 PM

is that like an object floating underwater that has water acting against it but has buoyancy acting to make it rise so that it's stationary but there's still a force trying to make it accelerate?

Pet_Sounds · 08-24-2019, 08:59 PM

Quote:

Originally Posted by Doug McClasky

is that like an object floating underwater that has water acting against it but has buoyancy acting to make it rise so that it's stationary but there's still a force trying to make it accelerate?

No, in that case the forces would balance so that the acceleration would be zero. The point with the ball is that its velocity is changing, even when it is instantaneously at rest at the top of its motion.

If the ball were sitting at rest on the earth, however, then its acceleration would be zero. Even though gravity pulls down on it, there's a corresponding upward force exerted by the ground that balances it out.

Being "at rest" (i.e., zero velocity) with nonzero acceleration only happens instantaneously.

The Batlord · 08-24-2019, 09:02 PM

Quote:

Originally Posted by Pet_Sounds

No, in that case the forces would balance so that the acceleration would be zero. The point with the ball is that its velocity is changing, even when it is instantaneously at rest at the top of its motion.

If the ball were sitting at rest on the earth, however, then its acceleration would be zero. Even though gravity pulls down on it, there's a corresponding upward force exerted by the ground that balances it out.

Being "at rest" (i.e., zero velocity) with nonzero acceleration only happens instantaneously.

But the air pressure on anything is still acting against anything sitting still so is still an active force, no? Like if all the air on earth suddenly disappeared everything on earth resting would "pop up"?

OccultHawk · 08-24-2019, 09:07 PM

PS

Are you going to tell him the newtons equal out in that case?

Pet_Sounds · 08-24-2019, 09:08 PM

Quote:

Originally Posted by Doug McClasky

But the air pressure on anything is still acting against anything sitting still so is still an active force, no? Like if all the air on earth suddenly disappeared everything on earth resting would "pop up"?

Huh?

OccultHawk · 08-24-2019, 09:09 PM

Air pressure adds weight.

The Batlord · 08-24-2019, 09:18 PM

Quote:

Originally Posted by Pet_Sounds

Huh?

I mean that the air pressure is adding permanent change to velocity that if removed would stop changing velocity. Like what's the difference between a ball hanging in midair and a ball sitting on the ground with air pushing down on it when if that air were removed would change/add velocity?

Pet_Sounds · 08-24-2019, 09:22 PM

Quote:

Originally Posted by Doug McClasky

I mean that the air pressure is adding permanent change to velocity that if removed would stop changing velocity. Like what's the difference between a ball hanging in midair and a ball sitting on the ground with air pushing down on it when if that air were removed would change/add velocity?

The forces on the ball hanging in midair aren't balanced. That's why it is only instantaneously at rest.
I think I'm interpreting your question right?

~~jwb~~ · 08-24-2019, 09:26 PM

Quote:

Originally Posted by Pet_Sounds

No, in that case the forces would balance so that the acceleration would be zero. The point with the ball is that its velocity is changing, even when it is instantaneously at rest at the top of its motion.

If the ball were sitting at rest on the earth, however, then its acceleration would be zero. Even though gravity pulls down on it, there's a corresponding upward force exerted by the ground that balances it out.

Being "at rest" (i.e., zero velocity) with nonzero acceleration only happens instantaneously.

That makes sense, I think.

Basically at the peak the ball is already set to move back towards the earth. So even though for an instant it isn't moving it will have a non zero velocity because at any given moment later it will have moved?

The Batlord · 08-24-2019, 09:31 PM

Quote:

Originally Posted by Pet_Sounds

The forces on the ball hanging in midair aren't balanced. That's why it is only instantaneously at rest.
I think I'm interpreting your question right?

Is there a describable difference between balanced and not balanced though?

08-24-2019, 09:07 PM	#62964 (permalink)
OccultHawk one-balled nipple jockey Join Date: Dec 2010 Location: Dirty Souf Biatch Posts: 22,006	PS Are you going to tell him the newtons equal out in that case? __________________ 2016 2017 2018 2019 2020 Member of the Year & Journal of the Year Champion Behold the Writing of THE LEGEND: https://www.musicbanter.com/members-...p-lighter.html

08-24-2019, 09:09 PM	#62966 (permalink)
OccultHawk one-balled nipple jockey Join Date: Dec 2010 Location: Dirty Souf Biatch Posts: 22,006	Air pressure adds weight. __________________ 2016 2017 2018 2019 2020 Member of the Year & Journal of the Year Champion Behold the Writing of THE LEGEND: https://www.musicbanter.com/members-...p-lighter.html