050 Force is change in momentum for a RipStik

This term the measurement of the downslope force was improved by tying a loop of jute twine to a post.

Board ahead of RipStik run

Ahead of class my mass and the mass of the RipStik were measured. The twine was also already prepared, attached to a post on the west side about halfway up the 21 meter run. The spoed trap was kept on the slope at the same length as last week: 1.8 meters.


Data after the run. The downslope time was stopped at top of speed trap. By keeping the speed trap on the slope there were no losses to friction. The change in momentum took 15.411 seconds for 21 meters minus 1.8 meters, a 19.2 meter run.


Five timers were deployed on the 1.8 meter on-slope speed trap. Four stopwatches and a cell phone. The median time was used in the velocity calculation. 

Spreadsheet

For g, which wasn't strictly necessary, the median time of experimental results was used in keeping with the spirit of the course.

The new spring scale arrangement produced forces of 10 to 15 Newtons. The change in momentum divided by the time was 14.77 Newtons. Agreement never gets better than that. I was stunned. I count on a lot of lost momentum which I attribute to friction. This provides a lead in for Thursday's lab. I had no idea what to say when the demonstration came out as predicted. Success is hard when your curriculum is predicated on failure.


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