HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 97

Example 2

Page 97 highlights

Example 2 Two ships are traveling according to the vector motions given below, where time is in hours and distance in kilometers. Illustrate their motion during the first ten hours. Ship A : Ship B : x A = ⎛ ⎜ ⎝ −100 ⎞ 500 ⎟⎠ + ⎛ ⎜ ⎝ 20 ⎞ −30 ⎠⎟t x B = ⎛ 200 ⎞ ⎜⎝ 400 ⎟⎠ + ⎛ −15 20 ⎟⎠t Enter the equations of motion as shown right. Now change to the PLOT SETUP view and set the axes to suitable values. Possible values are shown below. Now press PLOT to see the ships paths appear. As with the previous example, the value of TStep is chosen to allow visible motion. As the graph appears it can be seen that the ships do not collide, even though the final plot may make it appear that they do. To find the distance between the two ships at any time t, you can enter the equation F1(X)= ( X1( X ) − X 2 ( X ))2 + (Y1( X ) − Y 2 ( X ))2 into the Function aplet. Note that the active variable must be an X in the Function aplet instead of the T of the Parametric aplet but you can still refer to the Parametric functions X1 and Y1 even within the Function aplet. Graphing this function in the PLOT view of the Function aplet will allow you to find its minimum value. In this case the minimum separation of 13.74 km is achieved at t=8.68 hrs. 97

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Example 2
Two ships are traveling according to the vector motions given below, where time is in hours and
distance in kilometers. Illustrate their motion during the first ten hours.
100
20
Ship A
:
x
±
=
+
t
A
500
30
200
15
Ship B
:
±
=
+
t
x
B
400
20
Enter the equations of motion as shown right.
Now change to the
PLOT SETUP
view and set the axes to suitable
values. Possible values are shown below.
Now press
PLOT
to see the ships paths appear.
As with the previous
example, the value of
TStep
is chosen to allow visible motion. As the
graph appears it can be seen that the ships do not collide, even though
the final plot may make it appear that they do.
To find the distance between the two ships at any time
t
, you can enter
X
2
X
2
the equation
F1(X)=
(
X
1
(
)
X
2
(
))
+
(
Y
X
X
1
(
)
Y
2
(
))
into the
Function aplet. Note that the active variable must be an
X
in the Function
aplet instead of the
T
of the Parametric aplet but you can still refer to the
Parametric functions
X1
and
Y1
even within the Function aplet. Graphing
this function in the
PLOT
view of the Function aplet will allow you to find
its minimum value.
In this case the minimum separation of 13.74 km is
achieved at
t=8.68
hrs.
97