Re: L2-"Negotiating" a curve.

[Arlyn DeBruyckere <arlynd@HUTCH.K12.MN.US>]

Ludwik Kowalski wrote:

> As Bob wrote last night, the centripetal force is the normal
> component of the net force. The tangential component may
> or may not be present. Just something to think about while
> dealing with the three forces with which the road acts on the
> wheels of a tricycle.
>
> Arlyn DeBruyckere wrote: .....

Agreed.  It is a centripetal force *ONLY* if it is uniform circular motion.  The net
tangential force = 0.  If the net tangential force is not equal to zero I believe we
have moved beyond the high school level (L2) as we now need to consider the torques
involved to cause angular acceleration.  In this case we don't have circular motion
unless one of two conditions apply.  1) the centripetal force is changing to account
for the change in tangential speed or 2) we look at the limit of d(theta) so we have
circular motion only for and "instant" in time - otherwise we will have parabolic
motion (on probably a circular curve where the banking angle is changing throughout
the curve - much to complicated, IMO for a general high school situation).

In the case of the tricycle we have angular acceleration of the center of mass (CM) of
the tricycle through a parabola around the focus of the parabola as well as the
angular acceleration around the CM of the tricycle (causing it to "spin out" if the
frictional forces are not great enough).  And just because I can visualize the
situation doesn't mean I'm ready to start doing the calculations.

--
Arlyn DeBruyckere
Hutchinson High School