APS Excellence in Physics Education Award
November 2019

Education Prize Logo
Science SPORE Prize
November 2011

NSF Logo
The Open Source Physics Project is supported by NSF DUE-0442581.

Distance between two marks on a tensile test specimen post and replies

Return to the Distance between two marks on a tensile test specimen thread
Login to post to this thread

Distance between two marks on a tensile test sample
Jorge Garcia
5 Posts

I need to measure the distance between two moving marks on a silicone rubber specimen while the specimen is being pulled apart until it breaks.

To picture what I need to do, imagine two objects 3 m apart.  They both start travelling in the same direction at the same time, but the one in front is travelling at a much greater speed and the difference in speed changes with time. The task for Tracker is to measure the distance between the two moviing objects.

I've managed to get Tracker to track each mark individually, but not at the same time (otherwise I could have taken the difference between the x or y values of each mark). The online manual for tracker suggests that I can set up a "tape" and attach each end of the tape to each object/marker.

But I have not been able to get tracker to attach both ends of the tape to separate moving targets and autotrack the distance between the two moving targets

Has anyone tried to do something similar with Tracker? Do you have any hints?  Do you know of any video tutorials showing how to do this?


Replies to Distance between two marks on a tensile test sample

Solved (sort of): Distance between two marks on a tensile test sample -
Jorge Garcia
5 Posts

Basically I did what the Tracker help file says - (under the Tape Measure)

Attached a Marker to each end of a Tape Measure and used Auto Tracker to track first one Marker and then the Marker

I had not realised that this had to be done sequentially for each marker and that the values of the tape measure would still be updated after the second auto track

The values of length on the tape measure are automatically updated after the second Auto Track and the table of the tracked tape measurements can be cut and pasted into excel for further processing (A plot of stress vs strain).

I have not figured out whether auto tracker can auto track the two ends of the tape simultaneously, in the meantime, I'll make this work.


Thank you fore making Tracker available



OSP Projects:
Open Source Physics - EJS Modeling
Tracker
Physlet Physics
Physlet Quantum Physics
STP Book