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Korny_kid71
10-24-2005, 07:18 PM
ok umm well last year i was getting high 80's and low 90's. Now in grade 11 im a complete train wreck. In math im gettin a 71 and in physics im getin a 56... any who i need help with this one question, it has to do with tension force:

http://img402.imageshack.us/img402/4013/untitled1de.png
antonioledesma
10-24-2005, 08:30 PM
you should first check your textbook for those examples, there are tons of those. I could help you but I don't remember most of my physics courses and I would only confuse you (what an engineer.... :mrgreen:)

sorry :P
Apac102
10-24-2005, 08:37 PM
OH man...haven't done it in awhile but I know you first need to draw out the forces that are acting on the objects. This will be gravity, tension, Mue, etc. Then you will need to set the bottom box and use the equation F=ma. Then...huh...it gets a little cloudy for me. I know that both of the accelerations of each box will be the same so you will need to solve for a for each box and then set them equal to each other....Other then that, its been a couple of years and its hazy sorry.
gigdy
10-24-2005, 08:38 PM
Phuck Physucks
Apac102
10-24-2005, 08:39 PM
OH i forgot, in the bottom block, T=mg. So then if you have the tension for each block you can solve for other variables...good luck.
graywolf624
10-24-2005, 08:42 PM
Im a bit rusty... but..

left force: friction.. use mu and normal force of box 1

downward force: gravity box 2.

tension= left force assuming frictionless pulley and left force < downward force
A= downward force-left force/mass of system


Good luck.
SFDMALEX
10-24-2005, 08:47 PM
F=ma

In this case Fn=Fg
Ff=muFn

Fnet=Fg*a - Ff


So acceleration equals net force over the tottal mass of the two objects.

Once you find the accelration Tension in the string = mass of the 3kg block multiplied by the accelration that you got from part 1.


Fg*a is the hanging weight, the 1kg one.
graywolf624
10-24-2005, 08:51 PM
Well least I remember the accel part.

That is correct though now that I think about it. 5 years ago intro to physics is a little out of sight out of mind.
SFDMALEX
10-24-2005, 08:58 PM
Ok here you go mate, just made you this.


http://is-mad.com/upload/userfiles/SFDMALEX/physics.jpg
ZfrkS62
10-24-2005, 08:59 PM
::walks off to get asprin for sudden headache::
SFDMALEX
10-24-2005, 09:00 PM
correction A=F/m m=mass A plus mass B
homemade wrx
10-25-2005, 12:04 AM
Ok here you go mate, just made you this.


http://is-mad.com/upload/userfiles/SFDMALEX/physics.jpg
that's right direction of arrows but normally displayed in the other direction...my dynamics prof would take oints off :roll:
but who really cares we know what is meant...I see everyone already has things under control though...
your tension should be your normal force for the block a (F=m*a) 1kg*9.81m/s^2=x
and the use of mue is just time weight time the coefficient of friction so 3kg*9.81*0.2=x (force in Newtons)

but it's late and my brain doesn't work to well when its late....
abbor
10-25-2005, 06:36 AM
Well, I never heard the word tension force, but I guess you mean the force the object with m=3 kg is being dragged with...

Are my calculations correct when I say that a=2,7 and Ften=8,2 ?
Vansquish
10-25-2005, 05:56 PM
lol...and the only degreed physics mind on the forum shows up too late to do anything. Nice work guys :-D
graywolf624
10-25-2005, 06:02 PM
It's sad how you loose the ability to do things if you don't practise it every now and then. Ofcourse the basics are in mind, but not perfectly.
Not when you realize you understand the basic concepts and know where to look for the answers. Imho thats the true point of school.
homemade wrx
10-25-2005, 11:17 PM
It's sad how you loose the ability to do things if you don't practise it every now and then. Ofcourse the basics are in mind, but not perfectly.
Not when you realize you understand the basic concepts and know where to look for the answers. Imho thats the true point of school.
yeah, I remembered this stuff no problem back in high school when I went over it the day before....but now nose deep in senior ME crap the easy stuff kinda floats to the back ;)
Korny_kid71
10-26-2005, 04:01 PM
thanks for all the replies guys, i figured it out after a while of work, i kinda spaced out when the teacher explained the formula, and it was no where in the book so i couldnt learn from there. Thanks for everyone who helped me 8)
jon_s
10-26-2005, 05:39 PM
::walks off to get asprin for sudden headache::

Glad I am not the only one! Christ, it has been like...umm.. 8 or 9 years since I did any Physics lol :shock:

I am glad I took the educational path I did, having read all that lot :P
Zonda11
10-30-2005, 01:19 AM
thanks for all the replies guys, i figured it out after a while of work, i kinda spaced out when the teacher explained the formula, and it was no where in the book so i couldnt learn from there. Thanks for everyone who helped me 8)

Which book do you use?
homemade wrx
10-31-2005, 12:45 AM
tension
tension is when something is being pulled and compression is the opposite, when something is being squished/crushed together
abbor
10-31-2005, 07:50 PM
tension
tension is when something is being pulled and compression is the opposite, when something is being squished/crushed together

That's about what I thought... Except from some expressions, it's actually kind of amazing that the language of science makes people from different parts of the world, understand the same explanations....