<html><head><style type="text/css"></style></head><body><div style="font-family:times new roman,new york,times,serif;font-size:12pt"><div>And, as Edward knows, it is almost beyond belief that Newton did take into account all of these factors the very first time out of the chute in the Principia. Cheers, Alan </div><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"> <div style="font-family: arial,helvetica,sans-serif; font-size: 10pt;"><hr size="1">From: Edward Cherlin <echerlin@gmail.com> To: Yamandu Ploskonka <yamaplos@gmail.com> Cc: iaep <iaep@lists.sugarlabs.org> Sent: Sat, March 27, 2010 8:48:26 PM Subject: Re: [IAEP] Gravity for Beginners... On Sat, Mar 27, 2010 at 23:11, Yamandu Ploskonka <<a ymailto="mailto:yamaplos@gmail.com" href="mailto:yamaplos@gmail.com">yamaplos@gmail.com</a>> wrote: > How much lighter is a person in La Paz, Bolivia, than at sea level? > This actually was asked by a kid when I was there last time. > For practical purposes let's assume La Paz is 3.800 m over sea level Fascinating question. The simplest answer is that weight is inversely proportional to distance from the center, which we can approximate as 40,000 km/pi, or 12,742 km on average. This would give us a difference of roughly one part in 5,000 in weight for a difference of 4 parts in 10,000 in height. However, the distance between surface and center is actually 43 km greater at the equator than at the pole, so we have to do some much finer calculations to locate sea level at he latitude of La Paz. Then we have to decide whether to ask what the weights would be on a stationary Earth, or whether we will take rotation into account, resulting in apparent decreases in centripetal forces. If we wanted to be really finicky, we could take relativity into account also. ^_^ > On 03/27/2010 10:03 PM, Edward Cherlin wrote: >>> >>> If the kids could really measure accurately, >>> >> >> which can be done with a high quality pendulum, >> >> >>> >>> they would find that the >>> acceleration is not actually constant, but differs by about one part in a >>> million from 14 feet above the ground and at the ground level (due the >>> more >>> accurate inverse square Newton "Law"). >>> >> >> And if they had access to atomic clocks, they could observe the >> difference in the rate of passage of time at higher and lower >> altitudes, which are of practical importance in the clocks on GPS >> satellites. Measuring the deviations from Newton's Law in a falling >> object near the surface of the Earth requires greater precision than >> is available. It is observable with great difficulty in the precession >> of the orbit of Mercury around the Sun, and more clearly in binary >> pulsar systems. >> >> >>> >>> Please don't hesitate to ask questions. >>> >>> Cheers, >>> >>> Alan >>> >>> ________________________________ >>> From: Walter Bender<<a ymailto="mailto:walter.bender@gmail.com" href="mailto:walter.bender@gmail.com">walter.bender@gmail.com</a>> >>> To: Jeff Elkner<<a ymailto="mailto:jeff@elkner.net" href="mailto:jeff@elkner.net">jeff@elkner.net</a>> >>> Cc: <a ymailto="mailto:iaep@lists.sugarlabs.org" href="mailto:iaep@lists.sugarlabs.org">iaep@lists.sugarlabs.org</a> >>> Sent: Sat, March 20, 2010 12:41:01 PM >>> Subject: Re: [IAEP] Gravity for Beginners... >>> >>> kino will let you export your movie as a series of stills... I am sure >>> there are many Free multimedia programs with a similar capability. >>> >>> regards. >>> >>> -walter >>> >>> On Sat, Mar 20, 2010 at 3:17 PM, Jeff Elkner<<a ymailto="mailto:jeff@elkner.net" href="mailto:jeff@elkner.net">jeff@elkner.net</a>>  wrote: >>> >>>> >>>> Hi All, >>>> >>>> I'm working on a derivative version of "Gravity for 10 Year Olds" to >>>> use with my high school age students, which I'm calling "Gravity for >>>> Beginners": >>>> >>>> >>>> >>>> <a href="https://docs.google.com/Doc?docid=0ARq50A7-FeDXZGd2MnN0ODJfMjAwNmc0NHF4ZHI&hl=en" target="_blank">https://docs.google.com/Doc?docid=0ARq50A7-FeDXZGd2MnN0ODJfMjAwNmc0NHF4ZHI&hl=en</a> >>>> >>>> Day 2 has the following: >>>> >>>> "Show the students how to overlay frames from their videos to get this >>>> effect:" >>>> >>>> Can anyone point me to easy instructions on how to do this?  I can't >>>> really use the lesson without it. >>>> >>>> Thanks! >>>> >>>> jeff elkner >>>> _______________________________________________ >>>> IAEP -- It's An Education Project (not a laptop project!) >>>> <a ymailto="mailto:IAEP@lists.sugarlabs.org" href="mailto:IAEP@lists.sugarlabs.org">IAEP@lists.sugarlabs.org</a> >>>> <a target="_blank" href="http://lists.sugarlabs.org/listinfo/iaep">http://lists.sugarlabs.org/listinfo/iaep</a> >>>> >>>> >>> >>> >>> -- >>> Walter Bender >>> Sugar Labs >>> <a target="_blank" href="http://www.sugarlabs.org">http://www.sugarlabs.org</a> >>> _______________________________________________ >>> IAEP -- It's An Education Project (not a laptop project!) >>> <a ymailto="mailto:IAEP@lists.sugarlabs.org" href="mailto:IAEP@lists.sugarlabs.org">IAEP@lists.sugarlabs.org</a> >>> <a href="http://lists.sugarlabs.org/listinfo/iaep" target="_blank">http://lists.sugarlabs.org/listinfo/iaep</a> >>> >>> >>> _______________________________________________ >>> IAEP -- It's An Education Project (not a laptop project!) >>> <a ymailto="mailto:IAEP@lists.sugarlabs.org" href="mailto:IAEP@lists.sugarlabs.org">IAEP@lists.sugarlabs.org</a> >>> <a href="http://lists.sugarlabs.org/listinfo/iaep" target="_blank">http://lists.sugarlabs.org/listinfo/iaep</a> >>> >>> >> >> >> > -- Edward Mokurai (默雷/धर्ममेघशब्दगर्ज/دھرممیگھشبدگر ج) Cherlin Silent Thunder is my name, and Children are my nation. The Cosmos is my dwelling place, the Truth my destination. <a target="_blank" href="http://www.earthtreasury.org/">http://www.earthtreasury.org/</a> _______________________________________________ IAEP -- It's An Education Project (not a laptop project!) <a ymailto="mailto:IAEP@lists.sugarlabs.org" href="mailto:IAEP@lists.sugarlabs.org">IAEP@lists.sugarlabs.org</a> <a href="http://lists.sugarlabs.org/listinfo/iaep" target="_blank">http://lists.sugarlabs.org/listinfo/iaep</a></div></div> </div> </body></html>