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i thought its suppose to be t2-t1=fa but im wrong
why wouldnt the tension in A just be the weight of whats hanging from it?
it is but i dont understand why?
If there was no mass hanging from string A, would there be a tension in the string? no, because there would be nothing hanging from it (nothing pulling it down). BUT in this example there is something hanging from it, so we can se that the only thing that effects the tension on the string is the mass hanging from it.
what about the mass above it . isnt that mass pulling it up
If you had some string, and it was tied to a table with a rock hanging from it, the tension in the string would be due to the rock. Now if we took that same string and rock and hung it from a swing at a playground (similar to the system you have) then the tension in the string would still be due to the rock, (it doesn't matter where we hang the rock/string the tension in the string will be the same) |dw:1332720405241:dw|
gravity pulls downward, not upward for the most part
if you hang from a 50 lb bar or a 500 lb bar; the weight of the bar has no effect on how much gravity is pulling you down
the tension of the string is due to the rock that is pilling it down so what force is counteracting this foce
the tension in the string is counteracting gravity
so in the example u gave me what affects the rope is the mass that hangs from the rope.. it doesnt matter that there is another mass above it
i just thought that the mass would also be a source of tension
can u please draw me the free body diagram for my question
The picture you linked is a free body diagram...
i mean for the tension |dw:1332721306590:dw|
whats the force counteracting the tension
the mass is causing tension and pulling it down and i know weight is pulling it down butt whats pulling up
why does the mass cause tension? what is acting on the mass to casue it to cause the tension?
The tension in string B and C changes, But the tension in string A is just the force that W2 applies on it
Just think of it as, What is hanging from String A? Just W2 therefore that tension is JUST what W2 is pulling down on it.
in my book there is an example of a gymnast |dw:1332721554145:dw|
it shows a fbd of the rope .. in this case why are they showing the tension of the rope being pulled up the rope and then also being pulled down my the mass
( which is the gymnast)
Are you sure that the Vectors are labeled Tension and not Force?
yup they refer to it as t1 and t2
|dw:1332721889226:dw| should tension be pointing down???
well I think they mean that the tension force that the gymnast is applying to the string (T1) is the same as the roof (what ever the gymnast is hanging from) is applying (T2) But in an opposite direction. Just think, if there was no gymnast there would be no tension in the rope. As soon as the gymnast is hanging from it there is a tension. SO the only think that effects the tension is the gymnast. Thus the force he is pulling down on the rope = the tension force.
so are you saying that tension always pulls down?
if you put a rope in your hands and pull to each side; then the tension in the rope is not a downward force is it?
then lets stick to the problem at hand
for some reason it is just unclear to me that if u have mass pulling up and a mass pulling down why we would saying that tension is only due to w2
you have no mass pulling up
you have a force called tension created in the rope to counteract the force of gravity as it pulls on the mass
of course we assume the rope itself to be weightless
okay can u help me with another ?
dunno, i aint to adept at physics problems in general