Test:180 QNo:1

A uniform rope of mass m and length l is applied a force F on one end. What is the tension in the rope at a distance x from one end of the point of application of the force? (Assume uniform rope and that the cross section is 1 unit)

10 Answers

1
Anshit Mandloi ·

help out

24
eureka123 ·

λ=m/L
=>dm=λ.dx

Taking whole rope as system ,F=ma

Now take an element dx and distance s from where force is applied ..
m' x
=> m'=∫dm=∫λ.dx
0 0

=> m'=λx

Now see the forces on that element
=> F-T=m'a
=> F-T=(λx)(F/m)
=> T=F-mxF/Lm
=> T=F-Fx/L
=> T=F(1- x/L)
I know I made it a bit long...but that was done to elaborate the soln...I hope I am right

edited..missed a force..now its ok

1
Arshad ~Died~ ·

eureka i am getting the answer as f-fx/l

24
eureka123 ·

Is the rope verticla or horizontal ???

24
eureka123 ·

I took it to be horizontal...
I think u guys take it to be vertical

1
Arshad ~Died~ ·

eureka u hav neglected the force which is acting on the sytem....
the equation of motion should be
F-T=mxF/Lm

1
Arshad ~Died~ ·

and aveek ur solution is wrong....read the question carefully

24
eureka123 ·

oh yaa ..misse dit..actually I wasnt using pen or paper even..I was just typing..

1
Bicchuram Aveek ·

Taking the entire rope as one mass, F=ma; a=F/m;
Consider part AB.

F-T = Ma

Mass per unit length = m/L
Hence M=mx/L

T= F-Ma
= F-mxL.Fm
=F-FxL

The rope has been taken in a horizontal position (not a vertical one...I made a mistake in that). Cross-Secn. area has no use.

66
kaymant ·

That's right aveek.. you could have obtained that more simply if you considered the motion of the part of the rope leaving AB. Its mass is
mL(L-x)

And the acceleration F/m must be supplied by the tension. Hence,
T = mL(L-x) Fm = F(1 - xL)

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