Problem 1 (65 pts, suggested time 50 mins). An elastic string of constant line tension¹ T is pinned at x = 0 and x = L. A constant distributed vertical force per unit length p (with units N/m) is applied to the string. Under this force, the string deflects by an amount v(x) from its undeformed (horizontal) state, as shown in the figure below. р v(x) X L The PDE describing mechanical equilibrium for the string is d dv dx dx - p=0. (1) (a) [5pts] Identify the BCs for the string and identify their type (essential/natural). Write down the strong-form BVP for the string, including PDE and BCs. (b) [10pts] Find the analytical solution of the BVP in (a). Compute the exact deflection of the midpoint v(L/2). (c) [15pts] Derive the weak-form BVP. (d) [5pts] What is the minimum number of linear elements necessary to compute the de- flection of the midpoint? (e) [15pts] Write down the element stiffness matrix and the element force vector for each element.

Mechanics of Materials (MindTap Course List)
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Author:Barry J. Goodno, James M. Gere
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Chapter2: Axially Loaded Members
Section: Chapter Questions
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Problem 1 (65 pts, suggested time 50 mins). An elastic string of constant line tension1
T is pinned at x = 0 and x = L. A constant distributed vertical force per unit length p
(with units N/m) is applied to the string. Under this force, the string deflects by an amount
v(x) from its undeformed (horizontal) state, as shown in the figure below.
The PDE describing mechanical equilibrium for the string is
d
dx 
T
dv
dx
− p = 0 . (1)
(a) [5pts] Identify the BCs for the string and identify their type (essential/natural). Write
down the strong-form BVP for the string, including PDE and BCs.
(b) [10pts] Find the analytical solution of the BVP in (a). Compute the exact deflection
of the midpoint v(L/2).
(c) [15pts] Derive the weak-form BVP.
(d) [5pts] What is the minimum number of linear elements necessary to compute the deflection of the midpoint?
(e) [15pts] Write down the element stiffness matrix and the element force vector for each
element.

Problem 1 (65 pts, suggested time 50 mins). An elastic string of constant line tension¹
T is pinned at x = 0 and x = L. A constant distributed vertical force per unit length p
(with units N/m) is applied to the string. Under this force, the string deflects by an amount
v(x) from its undeformed (horizontal) state, as shown in the figure below.
р
v(x)
X
L
The PDE describing mechanical equilibrium for the string is
d dv
dx
dx
- p=0.
(1)
(a) [5pts] Identify the BCs for the string and identify their type (essential/natural). Write
down the strong-form BVP for the string, including PDE and BCs.
(b) [10pts] Find the analytical solution of the BVP in (a). Compute the exact deflection
of the midpoint v(L/2).
(c) [15pts] Derive the weak-form BVP.
(d) [5pts] What is the minimum number of linear elements necessary to compute the de-
flection of the midpoint?
(e) [15pts] Write down the element stiffness matrix and the element force vector for each
element.
Transcribed Image Text:Problem 1 (65 pts, suggested time 50 mins). An elastic string of constant line tension¹ T is pinned at x = 0 and x = L. A constant distributed vertical force per unit length p (with units N/m) is applied to the string. Under this force, the string deflects by an amount v(x) from its undeformed (horizontal) state, as shown in the figure below. р v(x) X L The PDE describing mechanical equilibrium for the string is d dv dx dx - p=0. (1) (a) [5pts] Identify the BCs for the string and identify their type (essential/natural). Write down the strong-form BVP for the string, including PDE and BCs. (b) [10pts] Find the analytical solution of the BVP in (a). Compute the exact deflection of the midpoint v(L/2). (c) [15pts] Derive the weak-form BVP. (d) [5pts] What is the minimum number of linear elements necessary to compute the de- flection of the midpoint? (e) [15pts] Write down the element stiffness matrix and the element force vector for each element.
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