Newton's laws of motion and friction
Monday Google's Science Journal software and a smartphone taped to a RipStik was used to estimate the lateral forces generated by swizzling on a RipStik. Perhaps the technology obscured the concept of force. The idea of using a smartphone as a key laboratory tool - accelerometer, luminosity, audiometer, oscilloscope, magnetic field strength - is too tantalizing to pass up.
This year the grit exploration benefitted from twelve grades of grit, up from the five in the past.
A list of weight coefficients of friction can be seen building on the board. The 0.75 would appear to be anomalously high. 0.24 and 0.207 are up on the board
Grit would consistently produce a random result that would be about 25% of the weight. In other words, the weight alone was able to explain the force of friction being seen, the grit had no particular impact on the sliding friction of the glass. Grit graphs were made far more rational this year by the use of grit particle sizes instead of grit grades.
Surface would remain unsettled. Both groups obtained a negative relationship between surface area and the force of friction. For both the relationship was not consistent. For one group, the data appeared to be non-linear leading to the use of a logarithmic relationship.
Wednesday I did the on sidewalk "PowerPoint" using signs on the posts to cover Newton's laws.
Sir Isaac Newton’s Three Laws of Motion
Definition:
Momentum = mv
One
An object at rest tends to remain at rest...
An object in motion tends to remain in motion…
...unless acted upon by an external force
∴ Momentum is constant
including Momentum = 0
Two
When acted upon by an external force,
The change in momentum is proportional to the force
Momentum is not constant
Force = Δ momentum ÷ Δ time
Force = Δmv ÷ Δt = m Δv÷Δt
∴ Force = mass* acceleration if mass is constant
Three
For every force there is an equal and opposite counterforce
Attempts to demonstrate the first law run afoul of the effects of friction, which leads naturally to a laboratory exploring friction.
Rayden and Benter explore the effect of grit
Juntwo and Heather with 12 grit grades
Tulpe and Suzanne exploring the effect of weight
Yummy working on grit in the afternoon
Venister and Ignathius study the effect of weight
Board notes.
Data showing the strongly positive linear effect of weight, the null effect of grit on the glass sled, and the negative relationship with surface area. Surface area used three double-sided sleds stacked to keep a constant weight.
Friday the students presented their findings to each other. The weight appeared to generate fairly consistent coefficients of between 0.20 and 0.36.
Saileen and Yummy
Limweidihwen and Justin
Suzanne and Tulpe
Margret and Selihter
A list of weight coefficients of friction can be seen building on the board. The 0.75 would appear to be anomalously high. 0.24 and 0.207 are up on the board
Rayden
Grit would consistently produce a random result that would be about 25% of the weight. In other words, the weight alone was able to explain the force of friction being seen, the grit had no particular impact on the sliding friction of the glass. Grit graphs were made far more rational this year by the use of grit particle sizes instead of grit grades.
Juntwo
Surface would remain unsettled. Both groups obtained a negative relationship between surface area and the force of friction. For both the relationship was not consistent. For one group, the data appeared to be non-linear leading to the use of a logarithmic relationship.
Myra
The last two weight coefficients can be seen above: 0.36 and 0.30. This would wrap up friction and the extended unit on motion.
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