Q9. A rectangular plate has a mass of 5.45 kg and is suspended vertically by a hinge on the top horizontal edge. The centre of gravity of plate is located 10 cm below the hinge.
A horizontal jet of fresh water 25 mm in diameter and flowing with a velocity of 5.65 m/s strikes the plate 15 cm below the hinge.
At this condition the plate is held in the vertical position by a compressed spring acting at its centre of gravity.
The flow rate of the jet is increased, and the plate is deflected to an angle of 30° to the vertical against the spring force which remains constant.
Friction in the hinge may be ignored.
(a) Calculate EACH of the following.
(i) The spring force holding the plate vertical; (4)
(ii) The increase in the jet velocity to deflect the plate. (8)
(b) Sketch the force diagram for the condition given in Q9 (a)(ii). (4)
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