Solve for elapsed time

05302018, 09:13 PM
Post: #1




Solve for elapsed time
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 

05302018, 10:56 PM
Post: #2




RE: Solve for elapsed time
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 

05312018, 11:43 AM
(This post was last modified: 05312018 11:48 AM by DrD.)
Post: #3




RE: Solve for elapsed time (Solved)
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 

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