# Homework Help: Pressure difference in a horizontal constant area pipe

1. Nov 18, 2012

### Blitz12345

1. The problem statement, all variables and given/known data

see attachment

2. Relevant equations
not sure if these are applicable because i dont think its steady state anymore
mass flow in=mass flow out
sum of forces in x direction= rate of momentum in-rate of momentum out
bernoulli's p+0.5ρ(v^2)= constant

3. The attempt at a solution
2.2a No
2.2b true, true, false as bernoullis assumption states inviscid flow, true if the given equations are true, true as the fluid is slowing down so resultant force is going in the left so pressure force at 2 is greater then pressure 1.
I am confused on making the correct assumptions could someone help me please?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

#### Attached Files:

• ###### Fluid mech question.png
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2. Nov 18, 2012

### atedinabox

2B is false. The amount of liquid entering the pipe has to be equal to the amount of liquid exiting it in steady operation. Friction won't cause a decrease in velocity (at the wall the liquid isn't moving anyway for viscous fluids). The friction will cause a head loss though. So you see the impact in a decrease in pressure This energy is converted into heat. Maybe now you can get the other parts as well?