Force of friction

Force of friction ran on a cold open, one-by-one mentoring start. A single student arrived by 8:00, instruction was one-on-one. No opening lecture or explanation. As students trickled in, each was either started on measurements or added as a partner to an existing solo experimenter.


Initially gathered data during the demonstration phase was echoed to the white board.


Austin and Yonard measure the effect of weight on the force of friction.


Vandasia and Tayshaun measure the effect of weight on the force of friction.

LizxyAnn and Bennie test the effect of grit size the force of friction.

Tommylee worked solo and found that in the force range where the green and blue spring scales overlap they do not produce the same result for a given load. To think to check for this possibility is deeply insightful. He understood the implicit assumption that the scales were both accurate, questioned that, and found that they were not. Absolutely brilliant. I know there is a discontinuity issue when the scales have to swapped out due to exceeding the range on the blue scale, but I also know that the discontinuity is small and not worth the potential confusion that might bring. 

Switching to using the green scales (0-500 gmf) from the start actually resolves this issue. This frees up the blue scales (0-250 gmf) for the grit groups who need the improved resolution.


Leann exploring weight versus the force of friction. The slot weights seem to be evaporating. Pairs only had a single 50, 100, 200, and 500 gram mass. Replacements are challenging to find and costly.

Meramy and Ariana working with an unloaded sled on different grits of sandpaper. At 11:00 the weight pairs started with the green spring scales.

Brithney and Pamella worked with weights.

Kayla and Valencia also measuring the effect of weights.


Pamella takes measurements while Brithney records the data.

Jay-brion and KC working on weight versus the force of friction 

Kealoha reads the spring scale


Board notes at end of the laboratory 

8:00 data. Orange circles are grit size versus force of friction 


The 11:00 grit size data displayed the characteristic rise in friction seen at small grit sizes in the past. This term that rise faded at the very smallest grit sizes. Detecting this feature appears to require careful measurements.

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