UG Community @ Ultimate-Guitar.Com For all you physics experts out there..
 Register FAQ Members List Search Today's Posts
Search:

10-04-2012, 10:40 AM   #21
cptcomet
Band

Join Date: Feb 2008
Location: UK
Velocity is speed in a certain direction. Seeings as the direction changes, i'd say that's your answer.
__________________
455 75 34 88

(´･ω･`)

Quote:
 Originally Posted by strait jacket Do you like being sigged or, like me do you feel strangely violated?

10-04-2012, 10:41 AM   #22
Kid_Thorazine

Join Date: Jul 2004
Location: KY
Quote:
 Originally Posted by Ssargentslayer Your answer did not need to be this long.

It wasn't initially, half of it is me second guessing my first answer.
__________________
make Industrial and/or experimental electronic music? Join my group!

Last.fm

 10-04-2012, 10:47 AM #23 Metalloy Registered User     Join Date: Apr 2010 ill give you an easy trick for you to use whenever you encounter such a problem: whenever there's change in movement from the original direction to the opposed direction, velocity changes sign, and at the point where the change of directions happened, is whete the velocity is equal to zero. other info, acceleration is always depending on an applied force, in your case gravity, and if there is no other forces applied during the movement, acceleration will stay constant, so in you case it will stay constant.
10-04-2012, 10:50 AM   #24
snipelfritz
Senior Fun Correspondent

Join Date: May 2006
Quote:
 Originally Posted by Metallica1554 The answer is velocity because it is a vector quantity, hence speed and direction are taken into account. The direction that the ball is travelling in changes throughout the flight, so on the way back down the velocity becomes negative.

This. In much better words than I could put it in.

Although I'm still not convinced that gravity and accelleration are the exact same thing and not just correlated.

However, I'm a Communications major and haven't had to do this kind of shit in the greater half of a decade.
__________________
BOOM-SHAKALAKALAKA-BOOM-SHAKALAKUNGA

10-04-2012, 10:50 AM   #25
ChrisBW
Registered User

Join Date: Jun 2009
Quote:
 Originally Posted by mulefish But wouldn't it need a positive acceleration to start with? Seeming as the ball is thrown? Velocity definitely changes though.

These problems always start a the time when the ball or whatever has left whatever is producing a force on it. So, what is happening is that something (persons arm) is producing a force on it. Once it has left the arm, it is now in free 'fall' motion. There is nothing to accelerate it upward anymore, only gravity to pull it down. The higher the velocity the longer it will keep moving in the upward direction. So, you would most likely have an acceleration that gives the object speed but think of it as a force that creates acceleration F = ma.

Quote:
 Originally Posted by snipelfritz Although I'm still not convinced that gravity and accelleration are the exact same thing and not just correlated.

Gravity is a Force that causes acceleration on objects within it's field. F due to gravity = (G)m1m2/d^2.

G is universal gravitation constant, m1 and m2 are masses of two objects, and those three terms divided by the distance between them squared gives the force of gravity. Which you can then apply to F = ma (I'm pretty sure... it's been awhile since I've done this).
__________________
I have a huge fear if rays.

Last edited by ChrisBW : 10-04-2012 at 10:57 AM.

10-04-2012, 11:08 AM   #26
Stugg334
Bristolian

Join Date: May 2009
Location: Bristol, UK
Yeah, it's velocity.
__________________
Quote:
 Originally Posted by slash11896 I picked up my guitar this morning and started playing next thing i know i cant stop playing In the key of A, the first letter or her name, I ended up recording a whole song in A.

Quote:
 Originally Posted by WhiskeyFace I like women with balls.

 10-04-2012, 11:30 AM #27 J-Dawg158 UG's Resident Dhampyr     Join Date: Nov 2008 Velocity. I think everyone's covered why it's not acceleration, but not why it's not position. Your problem states that it starts at Y=0, goes up and comes back to it's starting point at 0 therefore it was always positive and didn't change sign. __________________ I'm an Engeneer Enginear Enginere I'm Good at Math
10-04-2012, 11:41 AM   #28
whoomit

Join Date: Jul 2006
Location: Chandler, AZ
Quote:
 Originally Posted by magnus_maximus Gravity is just an acceleration. Gravitational force is caused by distortions in space/time.

10-05-2012, 05:25 AM   #29
whoomit

Join Date: Jul 2006
Location: Chandler, AZ
Quote:
 Originally Posted by magnus_maximus Seximus Decimus Aurelius. >_>

<_<

So it doesn't begin with a J?...

>_>

10-05-2012, 06:11 AM   #30
whoomit

Join Date: Jul 2006
Location: Chandler, AZ
Quote:
 Originally Posted by magnus_maximus

Do you have....

Ginger hair? >_>

 10-05-2012, 06:12 AM #31 laid-to-waste ...BlTCH     Join Date: Mar 2011 Location: Manchester, UK acceleration stays at -9.81m/(s^2). velocity is the property that changes, because the direction in which the object is travelling changes. SPEED doesn't change, velocity does. look into the difference if you don't know it already.
10-05-2012, 06:14 AM   #32
whoomit

Join Date: Jul 2006
Location: Chandler, AZ
Quote:
 Originally Posted by magnus_maximus No. GTFO. That's just insulting brah.

Oh, okay. So your surname isn't Johnston(e)?

10-05-2012, 06:17 AM   #33
lncognito
Registered User

Join Date: Dec 2011
Quote:
 Originally Posted by laid-to-waste acceleration stays at -9.81m/(s^2). velocity is the property that changes, because the direction in which the object is travelling changes. SPEED doesn't change, velocity does. look into the difference if you don't know it already.
Actually, the speed changes constantly as well. It just won't go beneath zero.
I realized halfway through writing this that this might actually have been what you meant, but meh... better to clarify it for confused TS (who really should have figured it out by now)

10-05-2012, 06:18 AM   #34
whoomit

Join Date: Jul 2006
Location: Chandler, AZ
Quote:
 Originally Posted by magnus_maximus Nope. So close, so close.

Without the 't'!?

 10-05-2012, 09:29 AM #35 MAC2322 UG's Twilight Sparkle     Join Date: Feb 2009 Location: Bogotá, Colombia. Forgive the red marker, I'm all out of other colors. Anyway, as you can see from the graphs, Velocity is the only quantity whose sign changes. I avoided using dx/dt and dv/dt for velocity and acceleration respectively since I doubt your Physics class is Calculus-based, but for those of you who do know Calc I, derivatives are what I was approximating with my Δy/Δt and Δv/Δt. I also marked the time t1 at which the object reaches its highest point so you could see how different quantities are changing (or not changing) at that time. __________________ My signature lacks content. It is, however, blue.
 10-05-2012, 09:35 AM #36 archenemyfan UG Addict     Join Date: Apr 2010 That was awesome. Thank you for taking your time to do that, I appreciate it. Also my physics class is calc based.
 10-05-2012, 09:39 AM #37 entity0009 UG's Null.     Join Date: Nov 2008 Location: Null. For those of you doubting that gravity is the only acceleration, whatever force that caused the ball (or whatever, I can't remember) to start its trajectory happened BEFORE t=0 and isn't a subject of study for the problem. A lot of people get confused when a is working in an opposite direction to v.
10-05-2012, 10:12 AM   #38
MAC2322
UG's Twilight Sparkle

Join Date: Feb 2009
Location: Bogotá, Colombia.
Quote:
 Originally Posted by archenemyfan That was awesome. Thank you for taking your time to do that, I appreciate it. Also my physics class is calc based.

No problem. If you have any other questions, feel free to ask (although I may not get back to you right away since I have to go to class myself).
__________________
My signature lacks content. It is, however, blue.

 10-05-2012, 10:19 AM #39 Arby911 Finding the Pattern     Join Date: Jul 2010 Ok, not a physics expert here, so could someone explain to me (using short words and small sentences) why acceleration isn't changing sign? Seems to me when the object leaves the starting point it's accelerating at -9.8 m/s^2 (or as the rest of us call that, decelerating). It then reaches apogee where it's at 0 m/s, and begins on its downward path at an acceleration of +9.8 m/s^2 ? As I've stated, this isn't my area of expertise, and while I have some small understanding of it, I'll not pretend to be an expert, so be gentle. __________________ “Ignorance more frequently begets confidence than does knowledge.” Charles Darwin Last edited by Arby911 : 10-05-2012 at 10:21 AM.
 10-05-2012, 10:28 AM #40 ChaosInside aspiring scientist     Join Date: Jul 2010 Location: Zanarkand Acceleration is always negative in this case. Initially it has an upward velocity because of the negative acceleration it will slow down until it is 0 m/s. At that point the negative accceleration will cause the velocity to go into the minus and accelerate it in the negative direction if you will. To make it a little easier to understand maybe, flip the axis so the acceleration is positive and the particle travels in the +y direction. In that case the velocity would get more positive with time. This works exactly the same, but in the negative y direction instead of the positive. Did this clear things up a bit? Also noteworthy: Velocity is a vector quantity. Speed is the norm of that vector and is is a scalar that is always greater than or equal to 0. This means that the speed is the square root of the sum of the squared components of the velocity vector. This is the same as the square root of the dot product of the velocity vector with itself, for those with a mathematical background. Edit: Clarification and typo's. Last edited by ChaosInside : 10-05-2012 at 10:39 AM.

 Thread Tools Rate This Thread Rate This Thread: 5 : Excellent 4 : Good 3 : Average 2 : Bad 1 : Terrible

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts vB code is On Smilies are On [IMG] code is On HTML code is Off
 Forum Jump Please select one User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home -------------------- UG Community     New Members Q&A Forum     The Pit     Archives Of The Best Threads         Music Theory Archives         Technique Archives         Bands & Artists Archives         Electric Guitar Archives         Bass Archives         Songwriting & Lyrics Archives         Bandleading Archives         Community Archives Music     Bands & Artists         Rock & Indie         Hardcore & Punk         Blues, Jazz & Other Guitar Styles         Metal         Other     Songwriting & Lyrics         Songwriting & Lyrics Contests         Songwriting & Lyrics Techniques     Recording         Tabs & Chords         Recording Contests         Original Recordings         Cover Songs     Tab Talk     Musician Talk         Bandleading         Singing & Vocals     Promote YOUR Band     Classifieds         Musician Ads         Gear Ads Instruments     Guitar Techniques     Acoustic & Classical Guitar     Electric Guitar     Bass Guitar     Guitar Gear & Accessories     Gear Building & Customizing     Drums Misc     Ultimate Guitar Feedback         Site Suggestions         Mobile Apps Feedback         Tab Pro Service Feedback         Bug Reports     UG Contribution

All times are GMT -4. The time now is 07:48 PM.

 -- UG Black Style -- UG Classic Style
Forum Archives / About / TOS / Advertise with us / Customer Support / Ultimate-Guitar.Com © 2016