Spring scale w/ Different Forces

[torq123]

I have two questions that I think are analogous (tell me if they are not).

1. If I have a spring scale and apply 50 pounds of force to one side and 40 pounds to the other, what would it read and why? (I think it will read 45 pounds because that is what the tension would be if it were a rope).

2. If I have a pipe with a supply pressure of 50psi and a return pressure of 40psi, what is the pressure on the sidewall of the pipe.

These are not homework questions--I was doing some plumbing recently in the lab and it got me thinking...

 

[UltrafastPED]

I think the tension in the rope is 90 lb, and same for the spring scale.

 

[Doc Al]

I think the tension in the rope is 90 lb, and same for the spring scale.

What if you pulled both ends with 50 lbs of force?