- #1
demonelite123
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I am given a rod with mass per unit length \mu, cross sectional area A, and under a tension F. I am also told that the tension F is uniform over the cross sectional area A. Find the stress energy tensor inside the rod.
I know that for the stress energy tensor T^{00} gives the energy density, T^{0i} gives the energy flux through a i-surface, T^{i0} gives the i-momentum density, and T^{ij} gives the i-momentum flux through a j-surface.
I have that T^{00} = \mu / A and that T^{0i} = T^{i0} = 0 since the rod is stationary so the particles have no net momentum. As for T^{ij}, if i assume that the rod is lying lengthwise along the x axis, then T^{11} = F/A since the momentum flux is the momentum per unit time per unit area or in other words the force per unit area. Then it seems to me that T^{ij} = 0 for all other entries since the tension acts along the x direction.
Therefore the stress energy tensor only has 2 nonzero entries on the main diagonal, and the rest of the entries are 0. Am I missing something here? It seems too simple a form to have and I am not sure if i took everything into account.
I know that for the stress energy tensor T^{00} gives the energy density, T^{0i} gives the energy flux through a i-surface, T^{i0} gives the i-momentum density, and T^{ij} gives the i-momentum flux through a j-surface.
I have that T^{00} = \mu / A and that T^{0i} = T^{i0} = 0 since the rod is stationary so the particles have no net momentum. As for T^{ij}, if i assume that the rod is lying lengthwise along the x axis, then T^{11} = F/A since the momentum flux is the momentum per unit time per unit area or in other words the force per unit area. Then it seems to me that T^{ij} = 0 for all other entries since the tension acts along the x direction.
Therefore the stress energy tensor only has 2 nonzero entries on the main diagonal, and the rest of the entries are 0. Am I missing something here? It seems too simple a form to have and I am not sure if i took everything into account.