Change in momentum is sort of proportional to the force applied

This remains my "failure is always an option" demonstration. Spring 2019 was the first term I tried this particular approach to showing that force is roughly equal to the change in momentum per second, and succeeded beyond my hope. Fall 2019 the force implied by the change in momentum exceeded the force reportedly applied. This term the force implied by the change in momentum was some 20% below the applied force.

This demonstration remains a full period demonstration, and covering quiz three this term overly shortened the period. I would recommend devoting the full period to the demonstration to better lay out the approach on the board prior to hitting the sidewalk. This term covering quiz three simply took too long.

Some of the equipment required

My mass plus the mass of the RipStik

Spring scale

The set up is essentially an acceleration from a velocity of zero across a three meter distance followed by a two meter "speed trap" to obtain my final velocity at the end of the three meters of acceleration. Calculations are done in terms of momentum rather than acceleration. This term a worksheet helped to organize the calculations.

Zero was from where I start most of my run, Trumaine was tasked with pulling. This term the 20 Newton pull force felt particularly anemic. Too slow if anything, not much pull. This called back into question whether shifting to the red spring scale and a 30 Newton force might be trialed.


I hold the rope for the first three meters....


...and then drop the rope for the two meter speed trap. Deceleration is an issue with the two meter speed trap, especially at low speeds.


Two timers timed the time over which my momentum changed, the first three meters. Two other timers timed the speed trap. The average time was taken.

This term the force implied by the change in momentum was 16 Newtons, four less than that which was theoretically applied. Trumaine did note that maintaining 20 Newtons was challenging.

More time would have permitted more rehearsals of maintaining the 20 Newton force. Fall 2018 in a failed run of this setup I may have taken upwards of 118 Newtons, thus 30 Newtons seems reasonably achievable. Everything always goes better with more speed, more force, no?

Comments

Post a Comment

Popular posts from this blog

Plotting polar coordinates in Desmos and a vector addition demonstrator

Image
In an earlier post I noted that Desmos did not directly plot polar coordinates. Not only was I incorrect, but Desmos responded to my blog to correct me! Although I had at some point seen that one could define a function f(x)=3x+5 and then have Desmos calculate f(6), I had not absorbed how this might be used to plot polar coordinates. The above works beautifully . Realizing that I could effectively program Desmos, I applied this thinking to demonstrating how to add two vectors when given the magnitudes m and the direction angles theta. The graph calculates the i and j components for the two vectors and then adds the vectors, graphically displaying the result while also providing information on the magnitude and direction of the vector sum. m1 and theta1 are the magnitude and direction angle for one of the two vectors, m2 and theta2 are the magnitude and direction for the other vector. All four are dynamically interactive and can be changed. The diagram purports to illustra...
Read more

Setting up a boxplot chart in Google Sheets with multiple boxplots on a single chart

Image
The  Google Statistics  add-on for Google Sheets can display multiple boxplots in a single chart. The key is the layout of the data. One column should be the variable by which the data is to be grouped, the other column should be the data to be box plotted. Set up the Statistics add-on with the data to be plotted as the variable, and the grouping column as the "by" variable. In this image I had deselected all but the boxplot option, the result was the appearance of the Moment, Standard errors, and Confidence intervals options. The default is apparently a 95% confidence interval for the mean. The result is multiple boxplots on a single chart with a common scale. The new tab that is created also quotes 95% confidence intervals for the mean. Note that as of 2018 the Google Statistics add-on cannot be found by search in the add-ons. In addition, as of May 2018 the add-on no longer verifies, possibly due to the add-on not having been updated since August 2017. One may ha...
Read more

Traditional food dishes of Micronesia

Image
Clara, Jennette, and Joanie presented ground hard taro cooked in an umw, effectively a hot rock oven. Pohnpeian: rotama. Pingelapese: sero. Mwoakillese: rodma. Mortlockese: Amahd. Kosrae: rodoma. After cooking in an umw the rotama is pounded with the petiole of a palm frond. Rotama is made from hard or swamp taro, known as mwahng on Pohnpei, mweian on Pingalap, pula in Mortlockese, and pahsruhk on Kosrae. In traditional times on the outer islands the women had primary responsibility for tending the taro while the men handled fishing and climbing tasks. Joesen and Noeleen presented fermented breadfruit from the outer islands of Yap such as Woleai and Eauripik. The raw ingredients were actually brought in from Yap, Noeleen prepared the maare.  The leaf wrap is ti leaf - Cordyline fruticosa. Pauleen, Barnson, Trisha, Verginia, Con-ray, and Maylanda from Kitti, Pohnpei brought in mahi umw, koahpnoair koakihr, and uht sukusuk. Above is breadfruit umw, mahi umw, o...
Read more