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Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

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F t (v) = B/v. 6<br />

There<strong>for</strong>e, the equation of motion <strong>for</strong> the system is<br />

dv/dt = i.(B/v) - (A 0 + A lv + A 2v 2 )]/m.<br />

When dv/dt = 0, Equation (3.21) will have the following <strong>for</strong>m<br />

v 3 + k 2 v 2 + k 1 v + k o = 0 '<br />

(3.2(;)<br />

(3.21)<br />

(3.22) '<br />

where k = -B/A 2' k 1 = A 0 /A 2' and k 2 = A 1 /A 2' which may be solved <strong>for</strong><br />

0<br />

v = V f . Of the resulting roots, one will be real and positive and will<br />

be the equilibrium speed of the train. 7<br />

Acceleration State. It is desired to determine estimates of a<br />

vehicle's acceleration time and the distance traveled during an accel-<br />

eration from v = 0 to v = V . The <strong>for</strong>mulas derived below could be<br />

generalized to include acceleration from any one speed to any other.<br />

However, these situations are not emphasized here, <strong>for</strong> they are ignored'<br />

in the linehaul-process functions. If the differential equation con-<br />

stituting the vehicle equation of motion, Equation (3.12): could be<br />

solved <strong>for</strong> velocity as a function of time (yielding an "acceleration-<br />

speed-time" function), 8 then the above time and distance estimates<br />

could be obtained. ,Specifically, if v = v(t) were the acceleration<br />

curve, then, in order to:determine acceleration time, one would obtain<br />

the inverse function t = t(v). The time required to accelerate from<br />

54

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