ENG102_HW8 - v < u reative to the ground. The velocity...

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DATE: November 16, 2011 DUE: November 22 (at or before 4:30), 2011 ENG102, homework set #8. 1. A rocket has before the start a mass m (0) = 4 × 10 3 kg. The exhaust velocity of the combustion products is u = 3 . 0 km/s. How much mass should be ejected per second if the rocket at its start from the surface of the earth should have an acceleration of g vertically upwards? 2. Let us assume that we have another rocket ready to go vertically upwards from the earth. Let us furthermore assume that the rocket engine burns its fuel such that the mass of the rocket with fuel decreases according to m = m 0 exp( - bt ) . Determine the minimum value of b such that the rocket can lift itself from the ground. Insert values u = 3 km/s and m 0 = 4000 kg. A v u M 3. Look at the figure above. A stream of water impinges on a block with mass M as indicated in the figure. At a certain time the block has a velocity
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Unformatted text preview: v < u reative to the ground. The velocity of the water before it hits the block is u relative to the ground, the cruss-sectional area of the water jet is A , and the density of water is ρ . The block has a kinetic friction coefficient μ k and the gravitational acceleration is g . a. Find the force that acts on the block from the water jet. b. Determine the steady state velocity of the block. c. if the static and kinetic friction coefficients are the same, what is the minimum jet speed for which the mass will move? d. What is the power of the action by the water jet on the mass M ? Niels Grønbech Jensen DEPARTMENT OF MECHANICAL AND AERONAUTICAL ENGINEERING | UNIVERSITY OF CALIFORNIA | DAVIS, CALIFORNIA 95616 TEL: 530.752.5335...
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This note was uploaded on 01/12/2012 for the course ENG 102 taught by Professor Eke during the Winter '08 term at UC Davis.

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