The pressure of water flowing through a pipe is measuerd by the arrangement shown in the figure.for the values give.
1the angle is.....degree.
2-the manometet fluid(h) hight is.....m.
3-The pressure in the pipe( PB) is ....KPa
4-the pressure differences (PB-PA)is ....KPa
2-the manometet fluid(h) hight is.....m.
3-The pressure in the pipe( PB) is ....KPa
4-the pressure differences (PB-PA)is ....KPa
Expert Answer
Problem
The flow of water from a reservoir is controlled by a 5-ft-wide L-shaped gate hinged at point A, as shown in Fig. P3–75E. If it is desired that the gate open when the water height is 12 ft, determine the mass of the required weight W.
Step-by-step solution
Step 1 of 3
Solve this problem by considering the sum of moments around the pivot point A. There are two moments in this system: the moment produced by the pressure from the water and the moment produced by the weight W.First consider the moment produced by the pressure from the water.Calculate the moment of the pressure force (MP) use
Here, the y-position of the center of pressure (yP) and the hydrostatic force (FR).The line of action of the force passes through the pressure center, which is 2/3 of the distance from the free surface (in this case, 12 ft). Find the center of pressure, free surface is 3 ft away from the pivot point A.
Comment Step 2 of 3
Find the hydrostatic force using the below relation
Because the system is open to the atmosphere P0 is zero and because the plate is symmetrical hC is equal to 6 ft.
Substitute 62.30 lbm/ft3 for
, 
for
, 6 ft for hC in the above equation 
Comment Step 3 of 3
Calculate the moment of the pressure force.
The moment of the weight (MW) must be equal and opposite to the moment of the pressure force.Define as the force of the weight (W) multiplied by its distance from the pivot point A.
Under the earth’s gravitational acceleration one lbf of weight is equivalent to one lbm of mass.Therefore the mass of the required weight W is
Comment
