Differences

This shows you the differences between the selected revision and the current version of the page.

activities:guides:cfairhockey 2013/08/27 09:28 activities:guides:cfairhockey 2013/08/27 09:32 current
Line 41: Line 41:
Students begin this activity by observing the motion of the puck on the airtable. The puck is pushed so that it passes close to, but does not strike, the pin in the center of the table. Students are asked to observe the motion of the puck. Then students are asked to respond, "On your small white board, make a plot of the potential energy." Don't give a more precise prompt. Students begin this activity by observing the motion of the puck on the airtable. The puck is pushed so that it passes close to, but does not strike, the pin in the center of the table. Students are asked to observe the motion of the puck. Then students are asked to respond, "On your small white board, make a plot of the potential energy." Don't give a more precise prompt.
 +
Line 55: Line 56:
{{activities:guides:cfforcesonair.jpg|}} {{activities:guides:cfforcesonair.jpg|}}
-**The most common example of potential energy that students see in an introductory course is gravitational potential energy, for which energy and height are proportional.  Some students may need to think about the fact that they can plot potential energy on the vertical axis when the puck stays on the surface of the table.**+  * The most common example of potential energy that students see in an introductory course is gravitational potential energy, for which energy and height are proportional.  Some students may need to think about the fact that they can plot potential energy on the vertical axis when the puck stays on the surface of the table. 
 + 
 +  * Many students will make a plot of $U$ as a function of both $r$ and $\phi$. 
 + 
 +  * A few students will make a plot of $U$ vs. time or angle.
-Other students may draw a parabola with the vertex centered at the origin, forgetting that the piece of thread means that there is constant potential energy out to some fixed radius.  Only beyond that radius does the potential energy increase.  +  * A number of students may plot the canonical variables ($U$ vs. $\phi$) but will draw a parabola with the vertex centered at the origin, forgetting that the piece of thread means that there is constant potential energy out to some fixed radius.  Only beyond that radius does the potential energy increase. 
This activity is a good opportunity to remind students of the arbitrariness of the zero of potential energy. This activity is a good opportunity to remind students of the arbitrariness of the zero of potential energy.

Personal Tools