Momentum Principle and Impact Transfer 1
The application of Newton’s second law of motion is straightforward in solid body mechanics hence the experiment aimed at applying the law in fluids. However, when applying the law in fluids, the concept of a control volume should be adopted in fluids into and out of which the fluid flows. The experiment assumes that the momentum per second crossing the surfaces of the control volume is equivalent to the forces in solid body mechanics. This experiment involves measuring the forces that a water jet discharging from a nozzle imposes on curved and flat surfaces and comparing these forces with those that would be expected from an application of momentum principle to the control volume that surrounds the water jet. From a theoretical consideration, when a jet of fluid impinges on a flat plate and is deflected through 90 degree, the application of the momentum principle predicts the force (F) inserted on the plate will be calculated as: F= pQu=pu2 A where p is the density of water, Q is the discharge, u is the jet velocity, and A is the jet area.
Hood, R. (2012) ‘Experiments and statistics.’ School of Mechanical Engineering, 2-43
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