Chronology |
Current Month |
Current Thread |
Current Date |

[Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |

*From*: "Bob Sciamanda" <treborsci@verizon.net>*Date*: Thu, 07 Jan 2010 12:19:37 -0500

This doesn't address your calculation, but

for a clever interactive lesson on least action, send your students to:

http://www.eftaylor.com/software/ActionApplets/LeastAction.html

Bob Sciamanda

Physics, Edinboro Univ of PA (Em)

treborsci@verizon.net

http://mysite.verizon.net/res12merh/

--------------------------------------------------

From: "Josh Gates" <jgates@tatnall.org>

Sent: Thursday, January 07, 2010 7:32 AM

To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>

Subject: [Phys-l] Action

Hi everyone,

I haven't dealt with action in a long time, so I'm a bit fuzzy on the

particulars at the moment. Here's what I'm trying to do:

Given a starting point (0,0) and an ending point (5m, 9.08m), I'm trying

to show that the parabolic path beginning with a 70 degree initial angle

from +x (the path given by N's laws, kinematics, etc.) minimizes the action.

Here's how I'm trying to do it (which apparently has one or more flaws):

- I made a spreadsheet, with the columns x, y, v, KE, PE, E, K-U

* x increments in .1 m steps from 0 to 5m

* y is a function of x, defining the path

* v is root(v_i^2-2gy), satisfying cons. of E

* KE and PE are defined in the ordinary way

* E is there to check my formulas, verifying cons. of E

* I average all of the K-U entries to give something similar to the action

Since the x steps are all the same, integrating K-U dx and dividing by

the total delta x should give me the same thing that the average does (I

think). It occurs to me now that there's a problem with paths that go

straight up at any point, but I'm willing to work with that later. My

current issue is that there are other parabolic paths that give a lower

K-U average than the correct path.

Anyone see where I went awry?

Thanks,

Josh

--

Joshua Gates

Physics Faculty

Tatnall School – Wilmington DE

Johns Hopkins Center for Talented Youth

_______________________________________________

Forum for Physics Educators

Phys-l@carnot.physics.buffalo.edu

https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l

**References**:**[Phys-l] Action***From:*Josh Gates <jgates@tatnall.org>

- Prev by Date:
**Re: [Phys-l] Action** - Next by Date:
**Re: [Phys-l] Action** - Previous by thread:
**Re: [Phys-l] Action** - Next by thread:
**Re: [Phys-l] Action** - Index(es):