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From: Gilman.ES@XEROX.ARPA@sri-unix.UUCP
Newsgroups: net.physics
Subject: Re: Physics question in a moving car
Message-ID: <13008@sri-arpa.UUCP>
Date: Thu, 30-Aug-84 13:00:00 EDT
Article-I.D.: sri-arpa.13008
Posted: Thu Aug 30 13:00:00 1984
Date-Received: Sat, 1-Sep-84 14:17:03 EDT
Lines: 17

Simply put, when the car is travelling straight, the dice are hanging
straight because there are no other forces on the dice than gravity.
Now, because an article in motion tends to stay in motion, when you turn
the car, the dice still tend to go forward, but the rear view mirror is
turning to the left.  When you consider the dice and the forces on the
dice, there is the force of the string composed of two components:  the
old force to counter gravity, and a new force caused by the car's
turning.  Now when the car turns at a constant rate, and goes in a
circle, the dice are always tending to go straight, but the car is
always turning.  The force due to the car's turning is called
centripetal force, since it is directed toward the center of the circle
around which the car is going.

By measuring the angle that the string makes to the vertical, you can
determine what the component of the force of the string is in the
direction of the center of the circle, and you have a crude centripetal
accelerometer.