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Re: Re: Re: O/T for you science buffs
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Posted by rhud on November 07, 2003 at 23:49:18 from (65.161.23.254):
In Reply to: Re: Re: O/T for you science buffs posted by Steve - IN on November 07, 2003 at 17:35:07:
me thinks you are pulling my leg. the Apollo example has little to do with the bullet example. but, i agree that for every action there is an equal but opposite reaction. in the Apollo example the acceleration of gravity added to the acceleration of the bullet in the opposite direction will increase the average velocity of the capsule. in the students question, the velocity of the speeding bullet is decelerated by gravity to zero and then accelerated by gravity back to it's high velocity.
in the bullet example V initial (after leaving the barrel) will be decelerated to V final (0) by earths gravity (no air ok?) at that time gravity (the same gravity that slowed the bullet) will pull the bullet back to earth. this time V initial will be 0 and v final will be the high velocity. since their is no air friction, the bullet cannot loose energy in any way, only trade kinetic energy for potential energy and then back to kinetic. the time up will be equal to time down, the gravity will be the same the v initial (up) and v final (down) will be the same. the balance of the two formulas is the same. vfinal squared = vinital squared + 2as a = gravitational acceleration (32.2 ft/sec/sec or 9.81m/sec/sec) s = distance traveled. there is no qualifing the formula as to if it is used with gravity or against gravity, only the sign of a changes (either positive or negative) the feather and hammer thing. the greater mass of the hammer also means a slower initial acceleration by gravity while the feathers lower mass means a faster initial acceleration. the only difference is final force applied by the two objects. the time for the fall is the same. you are correct, in that Galileo observed this experiment, you are however incorrect in that his observation showed both to hit at the same time. (legend of tower of Pisa) he used two spherical objects of the same size but of vastly different weights so that the present air would effect both equally. the formula for time of a fall such as this is: time= the square root of twice the distance dropped divided by the gravity constant. you will notice that neither weight nor mass is associated with the formula. I cannot account for the experiment you mentioned, but will look into it. if you will remember your scientific history, you will remember that the concept that was the basis of reletativity was a passenger on a train that accelerated to the speed of light. the formula e=mc squared actually uses the speed of light as a quantitative value not qualitative statement. It was the basis of Einstein’s later work, my examples deal with his earlier work. Again I agree with you in that I would not want to go that fast , especially with our roads in Virginia, but again in theory the passenger would both see forward and backward. Speed of light being constant therefore time itself must change as speed changes. if you consider the neurons as also part of the passenger then they are already at the speed of light and any displacement of signals either from the eye to the brain or from the brain to the eye being onlt relative to motion inside the car, not outside. I know this is tripe to some but it is important to the education of our children. The most complicated events must be simplified and studied before the actual complicated world be explained. that’s why its important to understand bullets in a vacuum before understanding bullets in real world air. By the way, Robert in W. Mi has it correct in that Hatcher did the experiment, for another discussion we could talk about why Hatcher theorized that in a perfect experiment,the bullet would also come back to land on its base not its nose. Man, I love this stuff. and for those that think the deal about doers and teachers, the best acceleration formulas i've ever seen are in The Machiner's Hand Book. you can bet your bottom dollar that machinest that "do" have that book, whether they share their knowledge with a student or not.
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