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You don't care.goldfish9776 said:So, is there any reaction at c ?
Why the reaction can't be drawn at c ?SteamKing said:You don't care.
A free body diagram can be drawn around the beam which excludes C. All that matters, as far as the equilibrium of the beam is concerned, is that the rope is in tension, which means that Tc > 0.
You don't care what the reaction at C is.goldfish9776 said:Why the reaction can't be drawn at c ?
i have tried to do in this way , but i do not get the ansSteamKing said:You don't care what the reaction at C is.
All you are interested in is finding the value of the distributed load w which keeps the rope in tension.
Looks messy.goldfish9776 said:i have tried to do in this way , but i do not get the ans
vertical force = 80+10-RB+TC-RC-2W=0 --------equation 1
total moment about A = 80(1) +10(3)+W(2)(5) = 0
110+10W= 2RB , RB= (110+10W) / 2 ------------equation 2
total moment about B = -80(1)-2TC +2RC +10(1) +W(2)(3) =0
TC-RC = (6W-70) / 2 ----equation 3
Sub equation 2 and 3 into 1 ,
i gt 90-(110+10W) / 2 + (6W-70) / 2 -2W = 0
i gt 18W= 0
why can't i do int his way ?
see it carefully , i did take the total moment about B ,SteamKing said:Looks messy.
Why don't you take moments about the pin at B? This will save you some work.
Remember, the reaction at C is not a load on the beam. The only load on the beam at point A is the tension in the rope, Tc.
goldfish9776 said:see it carefully , i did take the total moment about B ,
total moment about B = -80(1)-2TC +2RC +10(1) +W(2)(3) =0
if i ignore RC in my calculation , then my ans would be correct ?
so , i have redo the question , here's what i gt :SteamKing said:You haven't got any reasonable answer yet that I can see. Remember, the purpose of this exercise is to find the value of W which keeps the rope in tension.
Again, for the umteenth time, RC is not a load on the beam. Like haruspex said way back, you can't push on a rope.
goldfish9776 said:so , i have redo the question , here's what i gt :
80+10+2W -RB +TC= 0
moment about A = -80(1)+10(3) +W(2)(5) -2RB = 0
110+10W-2RB= 0
RB= (-110-10W) / 2
moment about B =
-80(1)+10(1) +2W(3) - TC(2) = 0
-70+6W-2TC= 0
2TC= -70+6W
TC = (-70 + 6W) / 2
Then you went and spoiled it by adding the moments summed about point A.90 + 2W - ((-110-10W) / 2 ) - ( (-70 + 6W) / 2 ) = 0
W=45N/m
is it correct ?
so , the W = 60/ 7= 8.57?SteamKing said:This is a superfluous calculation.
The moment calculation about point B looks good.Then you went and spoiled it by adding the moments summed about point A.
You can write only one moment equation. Discard the moment equation about A.
Use the moment equation about B to find W, such that TC is always in tension. (TC > 0)
Where did this come from?goldfish9776 said:so , the W = 60/ 7= 8.57?
from the moment about B aboveSteamKing said:Where did this come from?
You might want to check that original moment equation again. There's no factors of 60 or 7 contained within it.goldfish9776 said:from the moment about B above
A reaction at a pin support is a force or moment that is generated at a pin joint or pin support in a structure. It is a result of the structure's weight or external loads acting on it.
To calculate the reaction at a pin support, you need to consider the external forces acting on the structure and the support geometry. Then, you can use equations of equilibrium, such as summing forces or moments, to solve for the reaction at the pin support.
The different types of reactions at a pin support include vertical forces, horizontal forces, and moments. These can also be further broken down into components, such as vertical and horizontal components of a force.
The location of a pin support affects the reaction forces by changing the direction and magnitude of the forces and moments. A pin support at the end of a beam will have a different reaction force than a pin support at the middle of the beam.
Understanding reactions at pin supports is essential in the design and analysis of structures, such as bridges, buildings, and trusses. It helps engineers ensure that the structure is stable and can withstand the external loads acting on it. It is also crucial in determining the load paths and internal forces within a structure.