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MspEng
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1. I am trying to come up with an explanation as to why the force on a plate as provided by a jet of air, does not vary with the distance from the plate. We set up in a lab a vertical pointing air jet giving a constant output and gradually increased the height of the plate above the jet whilst measuring the force upon it as imparted by the jet using a Newton-metre. I have done all the calcs and am happy with their accuracy but the problem is our experiment gave a constant force of 1.4 N approx and the theory gives a value of 2.96 N. My big problem is i cannot explain why this is, the equations i provide below work on the assumption that the exit velocity of the nozzle (where the jet exits) is uniform, one dimensional (basically it obeys bernoullis equation) Below is my working for the theoretical value, and the experimental value of force was found to be approximately 1.4 N as stated before... hope someone can explain why there is such a gap between the therory and the reality!
F_P= m_e v_e=(0.039)(75.56)= 2.96 N
F_P= m_e v_e=(0.039)(75.56)= 2.96 N