Kedas Posted September 6, 2003 Share Posted September 6, 2003 for a completely closed AND ideal system you are right like I said in my previous message. Link to comment Share on other sites More sharing options...
YT2095 Posted September 6, 2003 Share Posted September 6, 2003 Kedas, LOL, a new page already mate we`re doing well I`ve gotta hand it to Blike, he sure knows how to start off a good topic Link to comment Share on other sites More sharing options...
Guest spacetime1 Posted September 27, 2004 Share Posted September 27, 2004 If I throw a ball straight up into the air' date=' is it still accelerating when its velocity is 0 (at the peak of its trajectory)? I say yes...but I just want to be sure[/quote'] YOU ARE RIGHT http://www.geocities.com/physics_all/index.html Link to comment Share on other sites More sharing options...
Nirav Posted September 28, 2004 Share Posted September 28, 2004 If I throw a ball straight up into the air' date=' is it still accelerating when its velocity is 0 (at the peak of its trajectory)? I say yes...but I just want to be sure[/quote'] Well... if i tell u honestly.... the ball even upon reaching its peak( where its speed is relatively zero to us) it can be considered to be accelerating........ this is given by the principle of equivalence( of A.Einstein) .... which tells that every object within the space- time curvature can be considered to b accelerating. so there 's ur answer man! Link to comment Share on other sites More sharing options...
ydoaPs Posted September 29, 2004 Share Posted September 29, 2004 it is accelerating. it's acceleration is -9.81m/s/s edit: for future reference, don't use geocities as a rescource. Link to comment Share on other sites More sharing options...
pi_of_9 Posted October 16, 2004 Share Posted October 16, 2004 I have a question that deals with acceleration but did not want to start a new thread as the question has probably already been addressed. If there was a large hole that extended from the North Pole through the center of the Earth to the South Pole and a person fell in...would he fall all the way through or stop at the center? If he stops at the center would he move up and down like a bungie jumper until he comes to rest? Link to comment Share on other sites More sharing options...
Callipygous Posted October 16, 2004 Share Posted October 16, 2004 I have a question that deals with acceleration but did not want to start a new thread as the question has probably already been addressed. If there was a large hole that extended from the North Pole through the center of the Earth to the South Pole and a person fell in...would he fall all the way through or stop at the center? If he stops at the center would he move up and down like a bungie jumper until he comes to rest? im guessing were assuming he survives things like pressure and heat and all that? he would pass though and start moving "up" on the other side untill the gravity slowed him enough to pull him back, like the bungie jumper. he would eventually stop due to friction with air. Link to comment Share on other sites More sharing options...
Cap'n Refsmmat Posted October 16, 2004 Share Posted October 16, 2004 If you did it on the Moon, however, with no air friction, he would just keep going from one end to the other without stopping. Link to comment Share on other sites More sharing options...
YT2095 Posted October 16, 2004 Share Posted October 16, 2004 last 2 posts are wrong. in the center (use a stone instead, it gets around the survivability probs) it`ll reach the middle , pass along it, be drawn back and eventualy reach equlibrium, with the graviation field, pulling equal in all directions. it will have effectively acheived gravitational rest mass. Link to comment Share on other sites More sharing options...
Callipygous Posted October 16, 2004 Share Posted October 16, 2004 how does that make my post wrong? and actually, with no air resistance it wont. just like with no air resistance a ball thrown straight up(or up at all, it doesnt even need to be straight) will come back down at exactly the same speed. Link to comment Share on other sites More sharing options...
YT2095 Posted October 16, 2004 Share Posted October 16, 2004 we`re talking the effects of gravity here, air resistance plays no significant part when falling to the center of a planet (Life Insurance may do though) Link to comment Share on other sites More sharing options...
Cap'n Refsmmat Posted October 16, 2004 Share Posted October 16, 2004 last 2 posts are wrong. in the center (use a stone instead' date=' it gets around the survivability probs) it`ll reach the middle , pass along it, be drawn back and eventualy reach equlibrium, with the graviation field, pulling equal in all directions.it will have effectively acheived gravitational rest mass.[/quote'] Say what? In the middle gravity will not affect it at all, since it will balance out. As you get farther out from the core gravity slows you down until at the top you stop. Then you fall right back down again. Link to comment Share on other sites More sharing options...
Callipygous Posted October 16, 2004 Share Posted October 16, 2004 we`re talking the effects of gravity here, air resistance plays no significant part when falling to the center of a planet (Life Insurance may do though) air resistance is the only thing that makes it so he will eventually stop. air resistance creates this thing called terminal velocity, without which he would build enough speed on his plunge to overcome the gravity at the center and "fall" back up to exactly the same height again. Link to comment Share on other sites More sharing options...
swansont Posted October 16, 2004 Share Posted October 16, 2004 Oscillate. Damped oscillation, in the presence of air. Fg=-GMm/r2, but for a uniform density, M varies as r3, since only the enclosed volume of mass contributes to the pull (Gauss's law) So you end up with something of the form F=-kx, which is Hooke's law, which applies to springs, etc. Simple harmonic motion. Link to comment Share on other sites More sharing options...
Callipygous Posted October 17, 2004 Share Posted October 17, 2004 Oscillate. Damped oscillation' date=' in the presence of air. F[sub']g[/sub]=-GMm/r2, but for a uniform density, M varies as r3, since only the enclosed volume of mass contributes to the pull (Gauss's law) So you end up with something of the form F=-kx, which is Hooke's law, which applies to springs, etc. Simple harmonic motion. super... english? Link to comment Share on other sites More sharing options...
jordan Posted October 17, 2004 Share Posted October 17, 2004 Assuming no friction, the person with fall back and forth forever taking the same time on each trip back and forth. Link to comment Share on other sites More sharing options...
[Tycho?] Posted October 17, 2004 Share Posted October 17, 2004 Wouldn't some energy be lost due to gravitational waves? Link to comment Share on other sites More sharing options...
swansont Posted October 17, 2004 Share Posted October 17, 2004 super... english? No, American. Why do you ask? The person would always feel a restoring force toward the center, if they are not at the center. And the force gets larger as they move away. In the absence of friction, or other dissipative force, this means that they would oscillate back and forth. Link to comment Share on other sites More sharing options...
RICHARDBATTY Posted October 17, 2004 Share Posted October 17, 2004 At the stop point the inertial forces and gravity cancel so there is no acceleration. Link to comment Share on other sites More sharing options...
jordan Posted October 17, 2004 Share Posted October 17, 2004 Don't you mean there is no velocity. Acceleration would be constant in this. Link to comment Share on other sites More sharing options...
Callipygous Posted October 17, 2004 Share Posted October 17, 2004 no, there would be no velocity at either end, there should be no acceleration for one instant in the middle, when no forces are acting on him, then his velocity carries him through and he starts accelerating back toward the center again. Link to comment Share on other sites More sharing options...
cyeokpeng Posted November 11, 2004 Share Posted November 11, 2004 Just think it like this. Though at the peak of its path its intstantaneous velocity is zero, take an elemental time after that. Its velocity will start to increase but in the opposite direction, since it is under the influence of gravitational acceleration g. So in effect, it still is accelerating at the peak, or else it would stay stationary there and not fall down, which you wil never see it happening like this. Link to comment Share on other sites More sharing options...
Panic Posted January 26, 2005 Share Posted January 26, 2005 yes there is accelleration ..... Acceleration is continuous and constant. just because a function has a maximum or minimum does not mean it stops there. the object reaches 0 m/s for only and infinitly small amount of time... it does not hang there like jordan! Link to comment Share on other sites More sharing options...
Callipygous Posted January 26, 2005 Share Posted January 26, 2005 acceleration is not continuous. there is no acceleration for one instant at the very bottom. it hits 0m/s at the peak(after falling back up), but it hits 0m/s/s at the very middle, when there is an equal gravitational force on all sides. note that there are two situations in question here. the first post about throwing a ball straight up and the second question about falling through the center of the earth. just incase we are talking about different things here. im talking about falling through the middle. Link to comment Share on other sites More sharing options...
JaKiri Posted January 26, 2005 Share Posted January 26, 2005 there is no acceleration for one instant at the very bottom. Net acceleration anyway. Link to comment Share on other sites More sharing options...
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