# Physics 20 Problem **URL:** \ **Category:** random\ **Created:** [April 12, 2006, 5:24am UTC](https://forum.kirupa.com/t/physics-20-problem/185278 "2006-04-12T05:24:42Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![TheCanadian](https://avatars.discourse-cdn.com/v4/letter/t/67e7ee/32.png) [@TheCanadian](https://forum.kirupa.com/u/TheCanadian)\ **Post date:** [April 12, 2006, 5:24am UTC](https://forum.kirupa.com/t/physics-20-problem/185278/1 "2006-04-12T05:24:42Z")
So I’ve missed the entire week of school and need some help with physics for my exam tomorrow. Anyways enough excuses, the question is this: A vertical loop on a roller coaster has a radius of 10.0m. At what minimum speed must a car travel at the top of the loop for it to remain in contact with the track? So if anyone is still awake and willing to help, I would greatly appreciate it. Thanks a bundle :mountie: PS: For anyone who does attempt this, the correct answer to the problem is 9.90m/s. Edit: Scratch that, just realized that some other equations applied to this problem, specifically: T = 2[pi]√(l/g) and v=2[pi]r/T I’ll keep this thread open in case I have some more questions πŸ™‚ ---
**Author:** ![anon1712571](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@anon1712571](https://forum.kirupa.com/u/anon1712571)\ **Post date:** [April 12, 2006, 5:35am UTC](https://forum.kirupa.com/t/physics-20-problem/185278/2 "2006-04-12T05:35:48Z")
Well thatis a pretty easy question to answer. Well actually it is about 9.8ms^2 rather than 9.9. Gravity is measured to be at a constant of 9.8 ms^2. Anything above this in an opposing direction will overcome the force of gravity. There could be many solutions past this, as you could have an incoming ramp of 1km (if u are talking about aproach length) But it needs to be at at least 9.8 (or 9.9. if you round it off to that) to balance out πŸ˜› Ahh looking at ur edit I can see ur using equations for centripetal motion eh? πŸ˜› hahahahah have fun… πŸ˜› ---
**Author:** ![TheCanadian](https://avatars.discourse-cdn.com/v4/letter/t/67e7ee/32.png) [@TheCanadian](https://forum.kirupa.com/u/TheCanadian)\ **Post date:** [April 12, 2006, 5:55am UTC](https://forum.kirupa.com/t/physics-20-problem/185278/3 "2006-04-12T05:55:26Z")
Thanks for the reply, hopefully you’ll be able to answer my new question: A girl swings 0.5kg teddy bear on a 0.3m rope in a vertical loop with a constant period of 1s. Estimate the tension in the cord when the teddy is in its: a) lowest position (answer: 10.8N) b) highest position (answer: 1.01N) I guess the real question is, what the deuce is tension? From my thinking I’m guessing it has something to do with centripetal force acting on the bear but, again, I would really appreciate some help with this πŸ™‚ ---
**Author:** ![anon1712571](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@anon1712571](https://forum.kirupa.com/u/anon1712571)\ **Post date:** [April 12, 2006, 6:05am UTC](https://forum.kirupa.com/t/physics-20-problem/185278/4 "2006-04-12T06:05:51Z")
Ah u just take away gravity from it πŸ˜› remember that there is more force at the bottom of a loop πŸ˜ƒ OMG OMG My post count says 1337 !!! ---
**Author:** ![TheCanadian](https://avatars.discourse-cdn.com/v4/letter/t/67e7ee/32.png) [@TheCanadian](https://forum.kirupa.com/u/TheCanadian)\ **Post date:** [April 12, 2006, 6:22am UTC](https://forum.kirupa.com/t/physics-20-problem/185278/5 "2006-04-12T06:22:58Z")
Alright, apparently I’m dumber than I look - unless I look bad in which case I would be exactly as dumb as I look and have two problems. Anyways, how would you calculate it? ---
**Author:** ![Phenex](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/phenex/32/686_2.png) [@Phenex](https://forum.kirupa.com/u/Phenex)\ **Post date:** [April 12, 2006, 7:28am UTC](https://forum.kirupa.com/t/physics-20-problem/185278/6 "2006-04-12T07:28:16Z")
Who ever said that g was necessarily equal to 9.8 ms^2? In Pakistan it’s almost 9.9. It varies every latitude or so dude! ---
**Author:** ![anon1712571](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@anon1712571](https://forum.kirupa.com/u/anon1712571)\ **Post date:** [April 12, 2006, 9:07am UTC](https://forum.kirupa.com/t/physics-20-problem/185278/7 "2006-04-12T09:07:44Z")
rofl well that is the standard that it is usually measured.πŸ˜› Bleh good point though heheh Anyways, u just need to remember that the force at the bottom of the loop (assuming u move at a constant) is 9.8(or 9) more than at the top of the loop. Plugin ur numbers into the formulae and u will get a nice answer πŸ˜› ( I haven’t touched centripetal motion for a while) ---
**Author:** ![Phenex](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/phenex/32/686_2.png) [@Phenex](https://forum.kirupa.com/u/Phenex)\ **Post date:** [April 12, 2006, 8:09pm UTC](https://forum.kirupa.com/t/physics-20-problem/185278/8 "2006-04-12T20:09:10Z")
Me neither πŸ˜›