Saturday, September 15, 2018

HP 20S and HP 21S: Approximating Stopping Distances

HP 20S and HP 21S:  Approximating Stopping Distances 

Introduction

We can approximate the stopping distance (in feet) of a vehicle on dry pavement given the vehicle's speed (in miles per hour, mph) by the formula: 

y = 3.85714285714*10^-2 * x^2 + 1.44504201681 * x + 0.64915966369

or

y = 27/200 * x^2 + 1.44504201681 * x + 0.64915966369

y:  stopping distance on dry pavement, feet
x:  speed of vehicle, mph

Assumptions:

*  The vehicle is assumed to be a passenger vehicle.

*  The reaction time is 1 second and the deceleration rate is 28 ft/s.

The program listed rounds all results to one decimal place.

HP 20S and HP 21S Program: Stopping Distance

The key codes for both calculators are the same in this program.

STEP KEY    KEY CODE
01   LBL B  61, 41, b
02   STO 0  21, 0
03   x^2    51, 11
04   ×      55
05   2      2
06   7      7
07   ÷      45
08   7      7
09   0      0
10   0      0
11   +      75
12   RCL 0  22, 0
13   ×      55
14   1      1
15   .      73
16   4      4
17   4      4
18   5      5
19   0      0
20   4      4
21   2      2
22   0      0
23   1      1
24   6      6
25   8      8
26   1      1
27   +      75
28   .      73
29   6      6
30   4      4
31   9      9
32   1      1
33   5      5
34   9      9
35   6      6
36   6      6
37   3      3
38   9      9
39   =      74
40   STO 1  21, 1
41   FIX 1  51, 33, 1
42   RTN    61, 26

Examples

Input:  25 mph,  Result:  60.9 ft

Input:  40 mph,  Result:  120.2 ft

Input:  65 mph,  Result:  257.5 ft

Note:  This time I am writing this blog entry direct in the Blogger compose box.  When I transfer text from either Jarte or WordPad to Blogger, all the formatting is lost.  And I don't want to format my text twice.  I will still save a backup copy.  I am very happy that Blogger compose box allows me to select special characters for the math symbols I need (the happy face is appropriate because it makes me happy!) 

Source:  

Glover, Thomas J.  Pocket Ref 4th Edition.  Sequoia Publishing, Inc. Littleton, CO. 2012

Eddie

All original content copyright, © 2011-2018.  Edward Shore.   Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited.  This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.  Please contact the author if you have questions.



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