HP 49g+, Руководство пользователя, Страница: 215 / 862

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The solution can be seen from within the SOLVE EQUATION input form by
pressing
@EDIT
while the
ex:
field is highlighted. The resulting value is
2.470833333333E-3. Press
@@@OK@@
to exit the EDIT feature.
Suppose that you now, want to determine the Young’s modulus that will
produce a strain of
e
xx
= 0.005 under the same state of stress, neglecting
thermal expansion. In this case, you should enter a value of 0.005 in the
ex:
field, and a zero in the
∆ T :
field (with
∆
T = 0, no thermal effects are
included). To solve for E, highlight the
E:
field and press
@SOLVE@ .
The result,
seeing with the
@EDIT
feature is, E = 449000 psi. Press
@SOLVE@ `
to return
to normal display.
Notice that the results of the calculations performed within the numerical
solver environment have been copied to the stack:
Also, you will see in your soft-menu key labels variables corresponding to
those variables in the equation stored in EQ (press
L
to see all variables in
your directory), i.e., variables
ex, ∆ T, α , σ z, σ y, n, σ x,
and
E
.
Example 2 – Specific energy in open channel flow
Specific energy in an open channel is defined as the energy per unit weight
measured with respect to the channel bottom. Let E = specific energy, y =
channel depth, V = flow velocity, g = acceleration of gravity, then we write
The flow velocity, in turn, is given by V = Q/A, where Q = water discharge,
A = cross-sectional area. The area depends on the cross-section used, for
example, for a trapezoidal cross-section, as shown in the figure below, A =
(b+m
⋅
y)
⋅
y, where b = bottom width, and m = side slope of cross section.
.
2
2
g
V
y E + =