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    • Re: Reading material

    Walter...

     I blew the dust off my son's old physics notes and came up with the following definitions...but would like your input.

    SPEED :   Rate in tilme at which something travels.   (I note no mention of direction, so I must assume it is not a vector quantity.)

    VELOCITY:  The time rate of change of a body in a specified direction.

    ACCELERATION:  The time rate of change of velocity with respect to magnitude or direction.

    (If we go by this, it provides a conundrum since it makes it seem as though we are describing a time rate of change of a time rate of change, here.  Something fishy about that thought !)

    Your statement, "Whenever you have a change in velocity, you have acceleration" does make sense to me, so long as that change is an increase in velocity.....but what about a change in velocity which is a decrease ?  Would that be defined as, "deceleration" ?

    Can we not have an increasing rate of acceleration ?  For example:  An object has a constant acceleration of 32'/sec/sec when dropped from a 1000' cliff.  Now, we affix a rocket to it and note that it gets to the ground a lot sooner.  Did we have an increase in the RATE of acceleration ?  Could we call that, "accelerated acceleration " ???

    Just trying to learn !

    Gordy




     

    From: Walter Simbirski <simbirsw@xxxxxxx>
    To: Gordon Hill <hillshead@xxxxxxx>
    Subject: Re: Reading material
    Date: Sun, 29 Oct 2006 18:32:42 -0700

    Gordy - any time you have motion that isn't in a straight line you have acceleration. The tip of the propellor blade may be travelling at a constant
    speed but the direction is constantly changing. Remember that velocity is a combination of speed and direction so the velocity is constantly
    changing even though the speed is constant. Whenever there is a change of velocity there is acceleration.
     
    By the way - thanks for the feedback on the web site. Simple and easy to navigate is good.
     
    Thanks
     
    Walter
     
     
    ----- Original Message -----
    From: Gordon Hill
    To: simbirsw@xxxxxxx
    Sent: Sunday, October 29, 2006 3:57 PM
    Subject: Re: Reading material

    Walter...

    Good idea on both counts.  I'll check out that website and let you know my thoughts.

    On thing, in particular, bothers me about acceleration being unidirectional, linear, and a vector quantity.

    How does one explain an airplane engine which starts slow, then spins in a circular manner faster and faster.  Does this propeller not accelerate ? It certainly isn't moving in a unidirectional or linear path, but rather a circular one.

    Can it be that an engineering way of looking at it is to envisage an infinite number of vectors with a resultant in a circular path ????

    Gordy




     

    From: Walter Simbirski <simbirsw@xxxxxxx>
    To: Gordon Hill <hillshead@xxxxxxx>
    Subject: Re: Reading material
    Date: Sun, 29 Oct 2006 10:29:53 -0700

    Gordy - I would be happy to put something together. It should take about a week or two. I've been planning
    on putting together an article on casting physics (simplified) for the Loop. This will give me some incentive
    to start sooner rather than later.
     
    In the meantime could you take a look at the website I've put together and give me some feedback? I used
    a program I was able to find on the web to convert the list of emails I have to an archive so the subject list
    is automatically generated by that program. We could spend some time going through the list to identify
    the ones that are most relevant and create an additional, better organized, list from that. I haven't included
    emails from the past few weeks - wouldn't take to long to do that at this point - I thought I should get something
    for people to look at sooner rather than later.
     
    The web site is   www.snapcasts.com
     
    follow the study group link for stuff related to the study group.
     
    Thanks
     
    Walter
     
    ----- Original Message -----
    Sent: Friday, October 27, 2006 8:35 AM
    Subject: Reading material

    Walter...

    Many of us non-physics / engineer folks in the Group, have had trouble really coming to terms with the basic understanding of:

    1.) Velocity  2.) Acceleration  3.) Linear acceleration as well as terms relating to application of force, torsional and otherwise.

    I wonder if you could help us by referring us to some basic texts or other writings  which will help clarify these and other physics terms in a way which is not too difficult for the lay person to understand ?

    Thanks !

    Gordy