Chronology | Current Month | Current Thread | Current Date |
[Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |
Hi Ludwik: You made two changes to your program. One was the fix I
suggested. But your second change was not only unnecessary but
actually incorrect, although it's only a smaller order error:
let dvR=-v0*dm/mR ! change of rocket m/s
let mR=mR-dm ! remaining rocket kg
let vR=vR+dvR ! new rocket speed
In this version of the program you calculate dvR from mR *before*
recalculating mR, whereas in your original program you calculated dvR
*after* recalculating mR. It was better the original way.
Roger dropped the second-order differential term dm*dvR. You should
not if you are going to let dm get rather large such as 10% of the
initial mass! By replacing the above three lines with:
let mR=mR-dm ! remaining rocket kg
let vR=vR-v0*dm/mR ! new rocket speed
you will not be dropping the second-order term and hence will improve
your program. (I leave the proof of this claim as an exercise.)
Cheers, Carl
--
Dr. Carl E. Mungan, Assistant Professor http://uwf.edu/cmungan/
Dept. of Physics, University of West Florida, Pensacola, FL 32514-5751
office: 850-474-2645 (secretary -2267, FAX -3323) email: cmungan@uwf.edu