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Sep 7, 2017 at 10:02 history closed sammy gerbil
Bill N
Jon Custer
By Symmetry
Kyle Kanos
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Sep 5, 2017 at 21:03 vote accept Peter
Sep 5, 2017 at 21:03 vote accept Peter
Sep 5, 2017 at 21:03
Sep 5, 2017 at 21:03 vote accept Peter
Sep 5, 2017 at 21:03
Sep 5, 2017 at 17:48 comment added Bill N Why use Mathematica? Set up a system of 3 equations and 3 unknowns: $v_1^2=2gL_1$, $v_2^2=2gL_2$, and $v_2=v_1+g\Delta t$. Solve for $g$.
Sep 5, 2017 at 11:53 history edited Mitchell CC BY-SA 3.0
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Sep 7, 2017 at 10:02
S Sep 5, 2017 at 10:44 history suggested Plexus CC BY-SA 3.0
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Sep 5, 2017 at 8:51 answer added Farcher timeline score: 1
Sep 5, 2017 at 6:21 history edited Qmechanic
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Sep 5, 2017 at 5:46 answer added kpv timeline score: 2
Sep 5, 2017 at 5:06 comment added user93237 .. the (unknown) drop time. You then have two equations with two unknowns (i.e., 't0' and $g$). The unraveling of the solutions doesn't appear easy (I used Mathematica), but it is possible to get expressions for the actual start time 't0' and the acceleration $g$ from the measured quantities of L1, L2, t1, and t2. You just need to measure the distances L1 and L2 very accurately and hope that the gate timers are accurate and have little jitter.
Sep 5, 2017 at 5:02 comment added user93237 A big problem with your setup is that, as you are aware, you have no way of knowing what the true t=0 start time of the ball drop is. Putting the first timer gate as close as possible to the drop point doesn't seem like a good option to me because the ball will not have v=0 when it triggers the first timer gate and a small timing error can lead to a large error in $g$ (as Mitchell below showed). A work-around may be to instead put the timer gates at distances L1 and L2 down from the drop point and measure their trigger times t1 and t2. The L1=g (t1-t0)^2/2 and L2=g (t2-t0)^2/2, where t0 is ..
Sep 5, 2017 at 4:28 comment added user93237 Your methods #2 and #3 can't be used because you have no way of measuring the instantaneous final velocity with your setup. Also, your calculation for $v_f$ is really a calculation of the average velocity. As for Method #1, that can be applied but I'm not sure that putting a timer gate near the initial v=0 drop point is the best position to get the highest measurement accuracy of g. Seems to me that you might get more accurate g measurement by locating the first timer gate a bit further down (and, of course, accurately measuring its position). You should so an error analysis of your setup.
Sep 5, 2017 at 4:10 answer added Mitchell timeline score: 3
Sep 5, 2017 at 3:54 review First posts
Sep 5, 2017 at 4:05
Sep 5, 2017 at 3:53 history asked Peter CC BY-SA 3.0