Re: What is Forced (accelerated) Motion?
From: Van Jacques (calccurve-test23_at_yahoo.com)
Date: 07/21/04
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Date: 20 Jul 2004 19:19:19 -0700
Herman Family wrote:
> The acceleration would be the angular velocity, squared, divided by
the
> radius, or 6.28 ft * 100 radians * 100 radians = 62800ft/sec^2
towards the
> center of the disk. This force is transmitted to the dot by the
disk.
> Should the dot leave the disk, it would leave in a straight line at
Assuming
> that there is no friction or added energy, the angular acceleration
is zero.
>
> Now, should your dot actually weigh something significant, then if it
is
> brought to the center of the circle, the disk will speed up,
conserving
> momentum.
>
> Michael
> "Spaceman" <Spaceman@realspaceman.com> wrote in message
> news:gWgLc.146782$Oq2.79653@attbi_s52...
> >
> > "Goran Jakupovic" <jakupovic_goran@hotmail.com> wrote in message
> news:cdj6es$tep$1@news.etf.bg.ac.yu...
> > } Mathematical definition of acceleration IS real world
> >
> > So, tell me,
> > How much is a dot on the edge of a 1 foot in diameter wheel
> > spinning at a constant 1000 revs per minute, accelrating?
> >
> > and when will such acceleration create a higher rev speed?
> >
> >
> >
The point is (for the nth time), speed and velocity are not the same.
Velocity is a vector in 3D, as is force and acceleration.
Speed is the magnitude (length) of the velocity vector.
In circular motion, the speed can be constant (if there is no
torque), but the velocity vector, which is tangent to the circle,
is constantly changing direction. It takes force to do this,
a force directed toward the center of mass. (Whence the term
central forces, like gravity and electricity.
Consider a small mass (a satellite) under the influence of the gravity
of a large mass (the earth or sun). Have the particle come in
from infinity, and consider what can happen to it. This is the
famous central force problem. I refer you to a physics text for
more on this elementary but fascinating problem. You will find
the test mass moving in a hyperbola if the motion is unbounded,
an ellipse (circle is a special case), when the mass is captured
(bounded motion).
Van
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