Friday, June 12, 2015

Tracker constant acceleration of 0.50 m/s2 example2

Tracker constant acceleration of 0.50 m/s2

There is evidence to suggest the motion made the students is average acceleration ax  = 0.35 m/s^2

Techniques used to determine the acceleration


  1. use an identifiable motionless object as reference, can reduce some the errors from a un steady camera view point.
  2. data analysis parabola fit to determine acceleration ax.

Model A

worksheet/lesson by: chan him nok
video by : RV_Rendao_jixuan_jingyan
model and reference by lookang
Download Link1 Link2

analysis suggests acceleration average ax = 0.38 m/s^2 instead of 0.5 assigned
worksheet/lesson by: chan him nok
video by : RV_Rendao_jixuan_jingyan
model and reference by lookang
Download Link1 Link2

Model B 2 parts motion


model B is suggested to better reflect the data
worksheet/lesson by: chan him nok

video by : RV_Rendao_jixuan_jingyan
model and reference by lookang
Download Link1 Link2

assume ax = 0.5, a t = 0 to 1.767 is selected to result in parabola fit parameter A = -0.247 so that ax = 0.49 close to 0.5 m/s^2
worksheet/lesson by: chan him nok

video by : RV_Rendao_jixuan_jingyan
model and reference by lookang
Download Link1 Link2

the rest of the data is fitted
worksheet/lesson by: chan him nok

video by : RV_Rendao_jixuan_jingyan
model and reference by lookang
Download Link1 Link2

model B is built based on the evidences of video analysis as a means for triangulate meaning of the analysis and the closeness of the fit is an indication of the correctness of model B to match real data.
worksheet/lesson by: chan him nok

video by : RV_Rendao_jixuan_jingyan
model and reference by lookang
Download Link1 Link2

My speculation 

you may have noticed the motion A and B do not match the new moving reference data for mass A.


i am using Tracker Models which are based on the fixed reference frame original at the beginning.
after i set a new track mass B as the new reference frame.
the models do not follow this new mass B as new reference frame, but instead continues to be based on the original fixed reference.
this is a problem for me unless i can call the x position of the new mass B into the model building interface, so that the model built can more closely matches that of the analysis data for mass A.

chance to suggest a work around or is it a "bug" in Tracker 4.88 and below?

hope the Tracker is improved based on this feedback!


Speculation 2

is it possible that there is a bug during exporting?

i will provide the raw files for your experimenting and repeating the process.

Raw files

  1. video with blank spaces , results in failure to encode as reported by Tracker at 99% completion. https://www.dropbox.com/s/sko97i2lxlv90y2/Video%20%288%29.MOV?dl=0
  2. good video with no blank spaces in file name , result in trz file sucess! https://www.dropbox.com/s/35bqmmhiidcq3s8/Video8.MOV?dl=0
  3. trk file https://www.dropbox.com/s/elujrmtkhee8pj4/RV_Rendao_jixuan_jingyan.trk?dl=0

End goal

  1. exported file https://www.dropbox.com/s/59e75ng3tbdyv5h/RVhimnokkinematics05.trz?dl=0 has a new mp4 but is not trim i believe, that results in the model that no longer matches the Mass A.

Current work around

to overcome this, i need to start the clip analysis back to frame 14.



thank you for creating Tracker, my favorite choice tool for Physics education!