Question

P1: 200kPa P2: 150kPa P3: 100kPa

can someone explain to me why P1A1 and P2A2 for Frx has to be minus with 100? e.g: -(200-100) ????

Assampllows 1The flow is steady md mcmpre.uble 2The weight ofthe Unim ind de water u) ส x corection ctor for ench inet nd oulet is givn to b -1.03 Propertles We take thesity of water to be 1000kp Analysh The flow velocities of the 3str ae We take the eatire Usection as the coatrol vohme We designate the borizoutal coordinate by s with the direction of inconming flow as being the positive direction and the equation for steady-ensacoal flow is ΣF ΣΑυν-ΣΑ"v we let the s-and :-coopoents of the anchoring force of the cone be Fe and Fe and assume them to be in the positive directions Then the momenhum equations along the x and : axes become vertical coondanate by . The mometm Substituting the given values 200-100)005 m) -1.03 (22 kg/ 2.80ms)+0 -Q733 KE-733 N 050-10) i21 0 10 ) IkN -93.1N The negative value for Fa indicates the assuned direction is wrong, and should be reversed. Therefore, a of 733 N acts on the flanges in the opposite direction. A vertical force of 93.1 N acts on the flange in the vertical direction Discussion To assess the significance of gravity forces, we estimate the weight of the weight of water in the U-tim and compare it to the vertical force. Assuming the length of the U-tum to be 05 m and the average diameter to be 7.5 cm, the mass of the water becomes , d(0.075 In) whose weight is 22 9.81 22 N, which is snch less than 93.1, but still significast. Therefore. disregarding the gravitational effects is a reasonable assumption if great accuracy is not required

Answer 1

Generally, we are habituated to use absolute pressure whenever pressure is mentioned.

Here, in the given question, gauge pressure is used. (NOT absolute pressure).

Guage Pressure = Absolute Pressure - Atmospheric Pressure

Atmospheric Pressure =1 atm ~ 100 KN/m2.

So, Guage Pressure = Absolute Pressure - 100 (all units in this equation is KN/m2).

This above formula is used in the given solution.