Solve for elapsed time - Printable Version +- HP Forums ( https://www.hpmuseum.org/forum)+-- Forum: HP Calculators (and very old HP Computers) ( /forum-3.html)+--- Forum: HP Prime ( /forum-5.html)+--- Thread: Solve for elapsed time ( /thread-10828.html) |

Solve for elapsed time - DrD - 05-30-2018 09:13 PM
With these provided values, (including the units), how could the prime be made to find the elapsed time? [CAS] vi:=18.51_(m/s); d:=79.8_(m); a:=11.17_(m/s^2); t=? d=vi*t + 1/2 * a*t^2; (Of course, the units could be removed, using left(var), and a mathematic result obtained; however it's the physical result that's desired). -Dale- RE: Solve for elapsed time - roadrunner - 05-30-2018 10:56 PM
Solve will do it if you use exact values. In CAS: d:=(vi,t,a)->vi*t+(1/2)*a*t^2 then: USIMPLIFY(solve((exact(d(18.51_(m/s),t,11.17_(m/s^2)))) = (exact(79.8_(m))),t)) gives: {2.47014692829_(s),−5.78438148514_(s)} -road RE: Solve for elapsed time (Solved) - DrD - 05-31-2018 11:43 AM
Thanks, for the very helpful information, Road! Using exact(value) is the key to success, here. (Good catch on that ...!) In my case, even though [CAS] [Exact] checkbox was checked, I see, (now), that it says it only affects the "Returned" values. (I wonder why it doesn't work, more generally?) [CAS] Code:
USIMPLIFY(solve(d = (vi*t+(1/2)*a*t^2),t)); t = {−5.78_(s), 2.47_(s)} -Dale- |