Re: Acceleration and curves

[Bob Sciamanda <trebor@VELOCITY.NET>]

The following is a directly palpable experience:  If you merely coast
around a tight curve at a constant speed, your centrifugal tendency to
slide across the seat toward the outside of the curve is only opposed by
the friction between you and the seat bottom .  If you add a forward
acceleration to the car's centripetal acceleration, your body is pushed
backward into the seat; this gives you additional friction (with the seat
back) to keep you from sliding across the seat.

With rear wheel drive, there is also an effect on the tire-road friction:
The forward acceleration pushes the turned front wheels harder into the
curve, increasing the availability of transverse friction for producing
the centripetal force.

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: Cliff Parker <cparker@EMPOWERING.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Thursday, August 19, 1999 8:46 PM
Subject: Acceleration and curves


> I did a good deal of driving while on vacation in the beautiful upper
> peninsula of Michigan the past ten days and as I drove a question kept
> popping into my mind.  As I drive through a curve there is the need to
> break just before and during the initial segment of the curve in order
> to maintain control of the vehicle.  After the vehicle is well into the
> curve however, I can take my foot off of the break and press on the
> throttle to increase speed and still maintain control.  What is going on
> here? It seems to me that the force the tires exert on the road during a
> curve of consistent radius must be the same as long as the vehicle is
> turning.  Why can I accelerate through the end of such a turn but not
> through the beginning?  I am thinking that perhaps rotational dynamics
> is playing a roll here or perhaps I am not really accelerating at all
> but only asking the engine to maintain the vehicles speed by pressing on
> the throttle.  It seems like I am going faster however.  As you can see
> I have been unable to discover an answer that satisfies me.  Someone
> please guide my thinking.
>
> Cliff Parker
> Physics Teacher
> Highland High School
> Highland, IL