386_Dynamics 11ed Manual

386_Dynamics 11ed Manual - ↑ Σ F y m' v By v Ay − ( )...

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Engineering Mechanics - Dynamics Chapter 15 Problem 15-119 A power lawn mower hovers very close over the ground. This is done by drawing air in at speed v A through an intake unit A , which has cross-sectional area A A and then discharging it at the ground, B , where the cross-sectional area is A B . If air at A is subjected only to atmospheric pressure, determine the air pressure which the lawn mower exerts on the ground when the weight of the mower is freely supported and no load is placed on the handle. The mower has mass M with center of mass at G . Assume that air has a constant density of ρ a . Given: v A 6 m s = A A 0.25 m 2 = A B 0.35 m 2 = M 15 kg = a 1.22 kg m 3 = Solution: m' a A A v A = m' 1.83 kg s = +
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Unformatted text preview: ↑ Σ F y m' v By v Ay − ( ) = P A B M g − m' v A − ( ) − ⎣ ⎦ = P 1 A B m' v A M g + ( ) = P 452 Pa = * Problem 15-120 The elbow for a buried pipe of diameter d is subjected to static pressure P . The speed of the water passing through it is v . Assuming the pipe connection at A and B do not offer any vertical force resistance on the elbow, determine the resultant vertical force F that the soil must then exert on the elbow in order to hold it in equilibrium. Neglect the weight of the elbow and the water within it. The density of water is γ w . Given: d 5 in = θ 45 deg = 384...
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This note was uploaded on 08/16/2011 for the course EGN 3321 taught by Professor Christianfeldt during the Spring '08 term at University of Central Florida.

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