What am I missing in my projectile motion error analysis?

[EvelynQW]

I’m really stuck on how to approach my physics lab report on projectile motion. My data shows the horizontal velocity stayed nearly constant, but my calculated values for the vertical acceleration are all over the place, and I can’t figure out what I’m missing in my error analysis.

[GeorgeOB]

I had a similar issue in my lab last term. The horizontal velocity looked steady, but the vertical acceleration bounced all over the place. When I computed a from position data with finite differences, a few noisy frames amplified the error and the numbers looked random. The error bars exploded, and I kept wondering if I was misestimating a.

[Nathan42]

Could the problem be how the vertical position was measured? If the reference height drifted during the run or the video scale wasn't consistent, the derived a would jump even if gravity is constant. I once forgot to reset the origin and saw crazy shifts.

[AlexanderXM]

I tried relying on video timing and frame counts, and the frame rate jitter killed the vertical numbers. The times weren't precise, so the derivative ended up noisy. I ended up treating the vertical part as noisy data rather than a clean parabola.

[Patrick11]

Maybe the issue isn’t gravity or the model at all but how we’re doing the error analysis. Are we accounting for systematic errors like lens distortion or calibration of the video scale? I’m not convinced.