Engineering Find v in electric circuit (nodal analysis, superposition)

[The_Lobster]

Homework Statement

Find the voltage v across the 5 Ohm resistor as shown in the attached drawing.

Homework Equations

Ohm's law, V=IR

The Attempt at a Solution

I have done plenty of these using different techniques, superposition/source transformation, nodal or mesh analysis, etc. But what puts me off with this one is that I don't really see where I should start. Am I right that I cannot turn the current source on the left into a voltage source because the two resistors in parallel have a node in between them?

What I have done so far is to devise two equations for the current in the two loops two the right of the drawing, disconnecting the current source (superposition), and I get: (I_1 = upper mesh)
Upper mesh:
0 = -9V + 35 I_1
Lower mesh:
0 = 9V + 15I_2

If I know put the current source back in place, and remove the voltage source, how would I then proceed to find the current through the 5 ohm resistor from th ecurrent source?

 

[The Electrician]

Replace the 9 volt source with a short; then the 20 and 15 ohm resistors will be in parallel and can be replaced with their equivalent. The 10 and 5 ohm resistors are similarly in parallel and can be replaced with a single equivalent. Solve that circuit for the voltage across the equivalent resistors. Now backtrack; you know the voltage across each parallel combination, and you can easily calculate the current in each resistor that makes up the combinations because you know the voltage across them.

 

[The_Lobster]

Thank you!

But what about the contribution from the voltage source once we put that back?

 

[The Electrician]

This is superposition.

You calculate the contribution from the current source with the voltage source shorted, and add that to the contribution from the voltage source with the current source open circuited.