# a.Find p1, the gauge pressure at the bottom of tube 1. (Gauge pressure is the pressure in excess of outside?

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atmospheric pressure) & Find v1, the speed of the fluid in the left end of the main pipe.Express your answer in terms of h1, h2, g, and either A1 and A2 or gamma, which is equal to A1/A2. the picture is below

http://session.masteringphysics.com/problemAsset/1…

anyone help me on this? i can’t figure it out. thank you.

• In this problem, there is no elevation change. From the principle of energy conservation, Bernoulli’s equation says that p + 0.5*ρ*v^2 is a constant anywhere on the middle of streamline. That means: p1 + 0.5*ρ*v1^2 = p2 + 0.5*ρ*v2^2

or: p1 – p2 = ρ*g*(h1 – h2) = 0.5*ρ*(v2^2 – v1^2)

= 0.5*ρ*v1^2*((v2/v1)^2 – 1)

= 0.5*ρ*v1^2*((A1/A2)^2 – 1) <since A1*v1=A2*v2>

Hence when p2 is set to be at atmospheric pressure (outside), p1 = ρ*g*(h1 – h2).

and: v1^2 = 2*g*(h1 – h2)/((A1/A2)^2 – 1)

or: v1 = sqrt{2*g*(h1 – h2)/((A1/A2)^2 – 1)}

where sqrt{} means the square root of {}.

• Thinner oils flows easier, but dont show s much pressure on a gauge. That is common and norm. 20W50 will always read higher than say 10W30. Now really 20W50 shouldnt have been used on a new rebuilt engine. Thats way too thick for a new, tight engine. 10W40 should be the thickest you run Airin the oil is norm. It’s called windage and crankcase pressure. As the crank, rods, etc moves in the crankcase the oil gets whipped around and causes air bubbles, foam at times, and plus the new rings takes time to seat and seal so you probbly have compression slipping past rings and entering the crankcase.. Norm takes 1500-2000 miles to fully seat rings Oil pressure, you need a min. of 10 psi per 1,000 RPM engine speed with engine at running temp.. Higher is much better than lower.. But you are fine with as low as say about 8-12 psi at a hot idle (15, 20, 30 psi is even better though)

• p1 = rho *g *h1