Plotting to find guesses

The main reason for plotting in the Solve aplet is to help you find initial guesses and solutions for those equations that have difficult-to-find or multiple solutions.

Consider the equation of motion for an accelerating body:

at2 x = v0t + ------

2

where x is distance, v0 is initial velocity, t is time, and a is

acceleration. This is actually two equations, y = x and y = v0 t + (at2) / 2.

Since this equation is quadratic for t, there can be both a positive and a negative solution. However, we are concerned only with positive solutions, since only positive distance makes sense.

1.Select the Solve aplet and enter the equation.

>$3/(7@ Select Solve 67$57a

>$/3+$@X _

>$/3+$@V >;@>$/3+$@T￿ >￿@>$/3+$@A￿ >;@>2.a$/3+$@T >;￿@ >j@2

2.Find the solution for T (time) when X =30, V =2, and

A =4. Enter the values for X, V, and A; then highlight the independent variable, T.

>180@

30 >(17(5@

2￿>(17(5@ *e,4￿>(17(5@ *e,*e, to highlight T

7-8

Solve aplet

Page 90
Image 90
HP 40G manual Plotting to find guesses, At2 x = v0t +, $/3+$@X, 180@ 30 175@ 2175@ *e,4175@ *e,*e, to highlight T