Question

Objective To determine the force generated by a jet of water striking on a surface Description of apparatus The supply is led to a vertical pipe terminating in a tapered nozzle. This produces a jet of water which impinges on the vane in the form of a Flat Plate, Hemispherical Cup, Conical Plate or 30° Angled Plate. The nozzle and vane are contained within a transparent cylinder; at the base of the cylinder there is an outlet by which the flow may be directed to the weighing tank. The vane is supported by a pivoted beam, which carries a jockey weight and is restrained by a light spring. The lever may be set to a balanced position (as indicated by the tally suspended from it) by placing the jockey weight at its zero position and then adjusting the knurled nut above the spring. Any force generated by impact of the jet on the vane may now be measured by moving the jockey weight along the lever until the tally shows that the lever has been restored to its original balanced position. Retaining screw Jockey weight Adjusting nut Cover plate Weigh beam pivot H TC Weigh beam -- Top plate Vane (flat plate shown) Tally Nozzle Supply hose Drain pipe Adjustable feet To weigh tank

Answer 1

step 1: first we have to calculate the theoritical result by considering no losses

force exerted by hose on flat plate $F_{f}$ = $\dot{m}.u$

= $\rho \cdot V\cdot u$

= $\rho \cdot Q\cdot u$

=

p. A.u.u

=

Y (distance in mm)	time (s)	theoritical result (F= $\rho \cdot A.u^{2}$ ) N	experiment results ( F= 4.g.y) N
80	68.94	3.28	3.139
70	73.42	2.89	2.746
60	78.55	2.529	2.354
50	84.95	2.162	1.962
40	96.12	1.682	1.569
30	107.88	1.338	1.177
20	218	0.326	0.784

now similarly we will calculate for conical plate

Y (distance in mm)	time (s)	theoritical result (F= $1.5\cdot \rho \cdot A.u^{2}$   ) N	experiment results ( F= 4.g.y) N
115	69.98	4.779	4.512
100	75.04	4.156	3.924
85	80.75	3.589	3.335

similarly we will calculte for hemispherical with F = $2\cdot \rho \cdot A.u^{2}$

discrepancy of the results are due to the possible following reasons

1. nozzle loss

2.vane plate losses ( sinosuidal wave creation)

3. pump suplly losses or suplly losses

PART 2: if jockey weight is measured wrong by 3 gram

new weight = 0.597kg

by moment equation force *015= 0.597.g.y

then force will be F= 3.98 g.y

error = 3.98/4 *100= 99.5

therefore error will be of 0.5 %

PART 3 : if distance is 4mm more then new distance =154 mm or 0.154 m

  force *0.154= 0.6.g.y

F= 3.89.g.y

error = 3.89/4 *100= 97.25

therfore error will be off 2.75%