20 replies to this topic

[princeofvegas]

I have always had this in the back of my mind forever. If you toss an object straight up in the air and it comes back down, when the object reaches its pinnacle does it come to a complete stop before coming back down or is it constantly moving. I would like your ideas and thoughts on this because this has been eating at me forever.

[Baniboy]

It is pretty much impossible to toss something straight up in the air but theoretically it does come to a complete stop.

Think it this way:

The ball is 100 grams so the earth will pull it with 1 Newton, you toss the ball with 6 newtons and it goes up.
The magnetic force of the earth wlll eat up of that 6 newtons until it's 1 N against 1 N, that is when it completely stops, but the 1 N left on the ball doesn't last forever because it doesn't generate it's own power (magnetic field, it does have a weak one but that pretty much pulls the earth towards the ball). Lets think the ball has the volume of 1 liter, and because 1 m3 of air weights about 1 kg and 1 liter is 1 dm3 so it will lift 100 g of the ball so it has neutral pulls the ball just flows in the air this is not realistic because balls with the volume of 1 liter don't usually weight 100 g now do they? well if they contain nothing but the outside shell.

he ball does reach neutral powers when it's at the pinnacle, so it does completely stop. But if you think in a larger scale, nothing stops completely:

The earth spins all the time, you can get the speed with this formula: 24 hrs/ 24 x 60 x 60 x 24 (to get the seconds) = 86400 seconds per day,
The circle around the earth is 40 000 000 m, so 40 000 000 m/24 = 1666666.6666... (let's say it's object "B" to shorten it a little)
the speed is 1667 km /hr (rounded number)

And also the earth is going around the sun and if I remember correct the speed was about 28000km/hr so we are constantly moving, even the particles of atoms vibrate all the time so technically the ball is constantly moving.

And may i remind you: this is not a thery or anything, all things said above are facts.

Hope I helped.

[vinay316]

The object has to come to a complete halt before it changes directioni.e when it starts to come down

[Baniboy]

vinay316, on Feb 16 2009, 03:12 PM, said:

The object has to come to a complete halt before it changes directioni.e when it starts to come down

not actually, only if it is moving to the exact opposite direction. And one thing, you can't define "stopping". You can compare it to another object, lets say earth but it isn't accurate. The speed of aircraft is compared to another object, earth. If it would be compared to air, it could be much faster/slower depending on the speed of wind. An Airplane can be said to move 1000 km /h but it can actually move 1200 km/h when it is going to the opposite direction of the wind since the air becomes resistants at those speeds. So we think it's 1000 km/h but the plane's engines are working for 1200 km/h. And like I already said, completely stopping is impossible.

Edited by baniboy, 16 February 2009 - 03:35 PM.

[Pankyy]

Nope, it's practically impossible due to the stated facts. The object you drop in the air and let it go down, is either going up with a very low speed or either going down. Imagine the speed is 10m/s, while it's going up it might go down to 0.2m/s and then it might down to -0.6m/s (negative meaning that it's going down instead of up). That's what I think though.

[Baniboy]

Pankyy, on Feb 16 2009, 06:11 PM, said:

Nope, it's practically impossible due to the stated facts. The object you drop in the air and let it go down, is either going up with a very low speed or either going down. Imagine the speed is 10m/s, while it's going up it might go down to 0.2m/s and then it might down to -0.6m/s (negative meaning that it's going down instead of up). That's what I think though.

"the object you drop in the air and let it go down" - that is not what princeofvegas said, he said that if he "tosses" an object up in the air.

It's not "going down" when it's moving to the exact opposite direction. Yes it has a opposite power that pulls it down but it doesn't actually move down before the power pulling it up is smaller than power pulling it down (magnetic force of earth).

And speed can't go to negatives, because directions are multidimensional (even more than 3 dimensions). You can point the direction and the drag but not negatives, it would mean something is beng pulled out of the universe as it has not speed and therefore no magnetic field and no existance, even fotons have their magnetic pull and speed.

Edited by baniboy, 16 February 2009 - 04:33 PM.

[Pankyy]

baniboy, on Feb 16 2009, 04:28 PM, said:

"the object you drop in the air and let it go down" - that is not what princeofvegas said, he said that if he "tosses" an object up in the air.

It's not "going down" when it's moving to the exact opposite direction. Yes it has a opposite power that pulls it down but it doesn't actually move down before the power pulling it up is smaller than power pulling it down (magnetic force of earth).

And speed can't go to negatives, because directions are multidimensional (even more than 3 dimensions). You can point the direction and the drag but not negatives, it would mean something is beng pulled out of the universe as it has not speed and therefore no magnetic field and no existance, even fotons have their magnetic pull and speed.

That's what in fact I tried to say, I think I messed up when I said: "let it go down", I was just mentioning the moment that the object that was tossed up in the air looses "positive" velocity and starts earning velocity in the other way.

I know it can't go negative, that's why I said that the negative means it goes to the other way... velocity is a vector, and it has module, direction, and way to go; yes, being a module means that it can't be negative. Going way too technical in a physics thread is hard to me since I lack of all the terms used in english, but I think someone could get what I meant.

[Baniboy]

Now i get what you ment.

Quote

It's not "going down" when it's moving to the exact opposite direction. Yes it has a opposite power that pulls it down but it doesn't actually move down before the power pulling it up is smaller than power pulling it down (magnetic force of earth).

Quote

I was just mentioning the moment that the object that was tossed up in the air looses "positive" velocity and starts earning velocity in the other way.

Yes, but,
It doesn't have and opposite velocity before the power pushing it up has a smaller pull than the one pulling it down. And by the way, it does have a moment when it has completely stopped moving, exept my explanations of how direction matters and what speed is compared to in the bottom of post 2.

[flashy]

vinay316, on Feb 16 2009, 02:12 PM, said:

The object has to come to a complete halt before it changes directioni.e when it starts to come down

Its vertical velocity may come to a complete halt - but it is merely impossible for you to throw a ball at 0 degress. Maybe so if you were on a planet with no atmosphere, since you have other effects on it - like the wind, earths spin etc..

In theory, a ball thrown at 0 degrees it will come to a complete stop and come down in the path exactly as it was launched from. But if you went slightly to the left, right up or down then the ball with have an angular path, and will keep its speed.

Like in this poorly made image

[mm22]

flashy, on Feb 17 2009, 03:22 AM, said:

In theory, a ball thrown at 0 degrees it will come to a complete stop and come down in the path exactly as it was launched from. But if you went slightly to the left, right up or down then the ball with have an angular path, and will keep its speed.

to be precise it will not come down exactly in the same path because of the Earth rotation beneath it... when the object is launched it has the same horizontal speed as the Earth (tangential component of the Earth spin), we launch it vertically so now it'll have a vertical component as well, assuming no friction/wind/etc the horizontal component of the velocity will stay unchanged while only the vertical component will be subjected to gravity as already explained.

Now, when the object reaches a certain height it will still be moving horizontally with the same speed it had on the surface, but since its distance from the center of the Earth has now increased it would need a higher horizontal (tangential) speed in order to maintain the same angular position it occupied on the surface. Being the speed lower than that the object will move a bit "backwards" and will land in a slightly different position from that it was originally launched from.

Of course all of the above effect is completely negligible if the object is launched only a few meters high, but we are talking about theory