Re: [Phys-l] the first law of motion

[Herbert Schulz <herbs@wideopenwest.com>]

On Nov 3, 2011, at 7:29 AM, Dr. Keith S. Taber wrote:

> Hm, I'm missing the unless...
>
> "a body in  motion TENDS to stay in motion"
>
> actually seems better to me than
>
> "a body in  motion WILL stay in motion"
>
> if the latter is not followed by an unless...
>
> If you are NOT going to give the conditions, then 'tends' is actually 
> more accurate.
>
> Keith

Howdy,

Why would you ever not give the condition under which it's not true. I always used ``constant rectilinear motion'' and also stated that meant a ``fixed speed in a fixed direction,'' i.e., constant velocity. I usually stated that the First Law concerned the motion of objects when there are NO forces acting on it and the Second Law was about the motion of objects when Forces act on the object. My emphasis with the Third Law was that Action-Reaction pairs NEVER act on the same object (A applies a force ON B the B MUST apply and equal and opposite force ON A).

Good Luck,

Herb Schulz
(herbs at wideopenwest dot com)