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0β(0.05) = 0.000 β 4.000 x 0.050 = β0.200; |
0β(0.05) = 1.630 + 0.000 x 0.050=β=_ 1.630. |
Now our main calculations begin: |
z(0.1) = 0.500β0.20x0.1 =_ 0.480 |
(0.1) = 0.0 + 1.63 x 0.1 =_ 0.163 |
r= V0.4802+0.1632 =_ 0.507 |
1/rα»Ά = 7.677 |
ΓΈβ(0.1) = β0.480 x 7.677 = β3.685 |
aβ(0.1) = β0.163 x 7.677 = β1.250 |
0β(0.15) = β0.200 β 3.685 x 0.1 = β0.568 |
0u(0.15) = 1.680 β 1.250 x0.1 = 1.505 |
+(0.2) = 0.480 β 0.568 x01 =_ 0.4238 |
(0.2) = 0.163 + 1.505x0.1 = 0.313 |
In this way we obtain the values given in Table 9-2, and in 20 steps or so we |
have chased the planet halfway around the sunl In Eig. 9-6 are plotted the z- |
and -coordinates given in Table 9-2. "The dots represent the positions at the |
succession of times a tenth of a unit apart; we see that at the start the planet |
moves rapidly and at the end it moves slowly, and so the shape of the curve 1s |
determined. Thus we see that we real do know how to calculate the motion of |
planetsl |
Table 9-2 |
Solution of duβ/dβ‘ = βΓΈΕ/rαΊΊ, duy/dt β= βα»₯/rαΊΊ, r = +2 + 92. |
Interval: = 0.100 |
α»rbiα»―t uy = 1.63 β=0 z=05 =0 at =0 |
β‘ un Uz Δβ α»₯ Uy Δα»₯ r 1/rΕ |
0.0 0.500 β4.000 0.000 0.000 |[ 0.500 | 8.000 |
β0.200 1.630 |
--- Trang 191 --- |
Table 9-2 |
t un Uz Δβ α»₯ Uy Δα»₯ r 1/rαΊΊ |
0.1 0.480 β3.685 0.163 β1.251 || 0.507 | 7.677 |
β0.568 1.505 |
0.2 0.423 β2.897 0.313 β2.146 || 0.527 | 6.847 |
β0.858 1.290 |
0.3 0.337 β1.958 0.443 β2.569 || 0.556 | 5.805 |
β1.054 1.033 |
0.4 0.232 β1.112 0.546 β2.617 || 0.593 | 4.794 |
β1.165 0.772 |
0.5 0.115 β0.454 0.623 β2.449 || 0.634 | 3.931 |
β1.211 0.527 |
0.6 | β0.006 -+0.018 0.676 β2.190 || 0.676 | 3.241 |
β1.209 0.308 |
0.7 | β0.127 +0.342 0.706 β1.911 || 0.718 | 2.705 |
β1.175 0.117 |
0.8 | β0.244 -+0.559 0.718 β1.646 || 0.758 | 2.292 |
β1.119 β0.048 |
0.9 | β0.356 +0.702 0.713 β1.408 || 0.797 | 1.974 |
β1.048 β0.189 |
1.0 | β0.461 -+0.796 0.694 β1.200 || 0.833 | 1.728 |
β0.969 β0.309 |
1.1 | β0.558 -+0.856 0.664 β1.019 || 0.867 | 1.536 |
β0.883 β0.411 |
1.2 | β0.646 -+0.895 0.623 β0.862 || 0.897 | 1.385 |
β0.794 β0.497 |
1.3 | β0.725 -+0.919 0.573 β0.726 || 0.924 | 1.267 |
β0.702 β0.569 |
1.4 | β0.795 -+0.933 0.516 β0.605 || 0.948 | 1.174 |
β0.608 β0.630 |
1.5 | β0.856 +0.942 0.453 β0.498 || 0.969 | 1.100 |
β0.514 β0.680 |
1.6 | β0.908 -+0.947 0.385 β0.402 || 0.986 | 1.043 |
β0.420 β0.720 |
1.7 | β0.950 -+0.950 0.313 β0.313 || 1.000 | 1.000 |
β0.325 β0.7Γ°1 |
1.8 | β0.982 +0.952 0.238 β0.230 || 1.010 | 0.969 |
β0.229 β0.774 |
1.9 | β1.005 -+0.953 0.160 β0.152 || 1.018 | 0.949 |
--- Trang 192 --- |
Table 9-2 |
t un Uz Δβ α»₯ Uy Δα»₯ r 1/rαΊΊ |
β0.134 β0.790 |
2.0 | β1.018 +0.955 0.081 β0.076 || 1.022 | 0.938 |
β0.038 β0.797 |
2.1 | β1.022 +0.957 0.002 β0.002 || 1.022 | 0.936 |
+0.057 β0.797 |
2.2 | β1.017 +0.959 || β0.078 +0.074 || 1.020 | 0.944 |
β0.790 |
2.3 |
Crossed zΓΈ-axis at 2.101 sec, .'. period = 4.20 sec. |
β = 0 at 2.086 sec. |
Cross ΓΈ at β1.022, .'. semimajor axis = ... = 0.761. |
0y = 0.T9T. |
Predicted time z(0.761)3β/2 = x(0.663) = 2.082. |
=1.0 α»Έ |
t= β _t=05 |
t=15βN * 05 7 |
t= 20^" =0 |
β1.0 β0.5 SUN 0.5 x |
Fig. 9-6. The calculated motion of a planet around the sun. |
Now let us see how we can calculate the motion of Neptune, Jupiter, UỦranus, |
or any other planet. lΓ we have a great many planets, and let the sun move |
too, can we do the same thing? Of course we can. We calculate the force on |
a particular planet, let us say planet number Β‘, which has a position #ΒΏ, ΒΏ, ZΒΏ |
(2= 1 may represent the sun, ΒΏ = 2 Mercury, ΒΏ = 3 Venus, and so on). We must |
know the positions of all the planets. The force acting on one is due to all the |
other bodies which are located, let us say, at positions #;,;,z;. Therefore the |
--- Trang 193 --- |
equations are |
mα» TU β NΒ¬_ GmimjVi S17) |
Δt = Tα» |
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