Ball on a hill

2006-12-30 21:30:42

#1

[RDH]Warlord: Quakecon Attendee; +17|6672|SLC, Utah, USA

In props to ATG, I wanted to start up another topic similar to the "plane on a treadmill" one. This one is a lot simpler, hopefully, and we may get to the bottom of it:

You have a hill (let's say 45 degree angle) with a long and powerful treadmill. Place the ball on the treadmill, and start the treadmill. If the treadmill runs as fast as it needs to to keep the ball on the treadmill, would the ball ever roll off? Would it ever reach a maximum RPM?

2006-12-30 21:32:33

#2

[RDH]Warlord: Quakecon Attendee; +17|6672|SLC, Utah, USA

Think about this for a minute, before replying quickly. The ball would spin faster, since it's on a hill. It'd never reach terminal velocity because it's not being affected by air resistance (being in place, at least primarily), so it would keep spinning faster and faster, and the treadmill would go faster and faster.

2006-12-30 21:34:42

#3

Mr.Casual: p-n*|3eergogglz; +136|6522|Minnesota eh

It would fall off eventually cause speed will keep picking up.

2006-12-30 21:38:12

#4

Dressed In Decay: Member; +14|6550

If the treadmill kept increasing speed with the ball then the ball would stay in the same exact spot.

2006-12-30 21:38:55

#5

Reciprocity: Member; +721|6594|the dank(super) side of Oregon

assuming there is a friction coefficient between the ball and the treadmill, there are no external factors; i.e. wind, or varying gravity, and the treadmill can match the balls speed up until a terminal velocity, it should stay in place.

'terminal velocity' is not just a reference to freefall.

2006-12-30 21:47:07

#6

viper313: One Shot, One Kill; +53|6655|Minnesota

Oh no.... Not again.

2006-12-30 21:53:17

#7

JOJOBA: my penis itches; +18|6546|Columbus, OH

the treadmill motor would fry if it went that fast for that long.

2006-12-30 22:29:43

#8

gene_pool: Banned; +519|6634|Gold coast, Aus.

Imo, the ball would pick up speed, and bump around a bit and fall down the treadmill.

2006-12-30 22:32:26

#9

Kamikaze17: Over the line!; +70|6762|Mark it zero.

the 45 degree angle might be a bit too much. it would probably have to be at less of an angle.

2006-12-30 22:39:24

#10

Locoloki: I got Mug 222 at Gritty's!!!!; +216|6653|Your moms bedroom

depends on the diameter of the ball

2006-12-30 22:40:36

#11

Ender2309: has joined the GOP; +470|6584|USA

it would immediately roll off.

because its on a hill, and the treadmill is rolling uphill, while the ball is rolling downhill, it falls off.

think about it.

the ball is going to spin front to top to back, if that makes sense.

the treadmill is moving uphill, which aides the roll, as it pushes the bottom foreward, and thus, the direction of spin. gravity pulls it down the hill, the treadmill makes it speed up, and it shoots down like a rocket.

2006-12-30 22:44:47

#12

Locoloki: I got Mug 222 at Gritty's!!!!; +216|6653|Your moms bedroom

its not aiding its spin, its helping drag it up to the next rotation of the ball, your groceries dont spin off the checkout at the supermarket everytime the conveyer moves

2006-12-30 22:55:28

#13

[RDH]Warlord: Quakecon Attendee; +17|6672|SLC, Utah, USA

The treadmill is not moving uphill itself, just the treadmill belt moving up.

Now, in this question, the treadmill is perfectly capable of running at whatever speed it can for however long it needs to. Let's assume the belt is so smooth and the ball is so smooth that there is no way it would start bouncing.

Terminal velocity, btw, only applies to an object falling. In a vacuum, an object would never achieve terminal velocity, since there is no air friction to slow it down. Similarly here, the ball never really moves (if the treadmill is doing it's job), so no air is pushing it to prevent it from speeding up.

Wouldn't this situation (of which lots of physics questions use situations like mine, so don't knock it) have no end? The belt could constantly speed up, to keep the ball in place. So, effectivly, we've created a situation where we can go any speed (in theory, faster than light?) with no air resistance...

This situation facinates me, as much as the idea of a perpetual motion machine...

Last edited by [RDH]Warlord (2006-12-30 22:57:16)

2006-12-30 22:58:33

#14

Locoloki: I got Mug 222 at Gritty's!!!!; +216|6653|Your moms bedroom

negative, the ball has a force of 9.82m/sec^2 pushing down on it, so technically it is falling, it will no longer accelerate downwards when it hits terminal velocity on the planet earth

i think it would be able to hold the constantly falling ball. The diameter of the ball times the speed of rotation(which is imparted by gravity), or the distance the ball "falls" on the treadmill in one spin, if the treadmill can move the ball back to the starting height of the spin, before it starts to spin again

Last edited by Locoloki (2006-12-30 23:24:46)

2006-12-31 09:15:23

#15

[RDH]Warlord: Quakecon Attendee; +17|6672|SLC, Utah, USA

Again, Terminal Velocity only applies to objects falling. The only reason things achieve that (and the TV is different for different shaped/sized objects) is because of the air resistance.

http://en.wikipedia.org/wiki/Terminal_velocity

2006-12-31 09:28:39

#16

CTD-CaptainBuck: BLEEDING BLUE; +71|6781|Tenn

depends on the ball actually. sumthing with relative size and mass of a ping pong ball, would not be able to handle all the forces and would bounce off the treadmill. now sumthing like a golf ball, will not be as succeptible(sp?) to bouncing, however it will eventually bounce and/or roll straight off because it will exceed its maximum cfm.

2006-12-31 09:30:16

#17

stkhoplite: Banned; +564|6492|Sheffield-England

what if the treadmill shuts off by accident?

2006-12-31 09:35:32

#18

Storgie: how about this thread for whiners; +15|6588|federal way washington

i think the ball would fall off, no way the treadmill could keep up plus the ball would not roll in a single straight line down but find the line of least resistance and find a wall off the treadmill, most like off a side.

2006-12-31 09:47:37

#19

Kmar: Truth is my Bitch; +5,695|6614|132 and Bush

The answer is in the make up of the ball. Material, weight, etc.. There are way too many factors left out of this equation.

Xbone Stormsurgezz

2006-12-31 10:38:55

#20

FFLink: There is.; +1,380|6704|Devon, England

Ender2309 wrote:
it would immediately roll off.

because its on a hill, and the treadmill is rolling uphill, while the ball is rolling downhill, it falls off.

think about it.

the ball is going to spin front to top to back, if that makes sense.

the treadmill is moving uphill, which aides the roll, as it pushes the bottom foreward, and thus, the direction of spin. gravity pulls it down the hill, the treadmill makes it speed up, and it shoots down like a rocket.

Makes perfect sense. I think this is your answer.

2006-12-31 12:16:50

#21

224th R0ck3tpack: Hostile pansy spotted!; +8|6442|NH

Treadmills are textured, and it would hit a texture spot eventually, and the faster it's going the more likely it is to hit that texture patch like a jump.

Last edited by 224th R0ck3tpack (2006-12-31 12:17:12)

2006-12-31 12:27:50

#22

spray_and_pray: Member; +52|6504|Perth. Western Australia

We can try this out but the texture of the ball also counts like a shiny soccer ball or a bumpy basketball.

BF2S Forums Ball on a hill

Ender2309 wrote:

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