Re: inertia demo

["John S. Denker" <jsd@MONMOUTH.COM>]

Larry Woolf wrote:
> 3. Push a car to accelerate it. Have a number of students each push on a
> scale that is on the car

This is an excellent idea.  Even rather young kids can
push large objects, and get unforgettable "hands on"
lessons about inertia.

See the second half of:
http://lists.nau.edu/cgi-bin/wa?A2=ind0109&L=phys-l&P=R34680

A 10kg block of dry ice has noticeable inertia and (if
you do it right) has impressively low friction.  But cars
have pretty low friction, too, and you can borrow a
megagram of car more easily than you can lay hands on
large pieces of dry ice.

You can come up with all sorts of instructional games,
such as tug-of-war with a megagram of inertia in the middle.
You can also do fun things with pulleys.

I'd like to stress the need for safety precautions.  You
can't tolerate even a small risk of a student getting
run over.  Have a responsible person in the driver's seat,
ready to apply the brake if things get out of hand.  And
apply forces to the car via ropes, so that people can
maintain a reasonable distance from the wheels, especially
when they're trying to slow down(*) the car.

=================

*) Terminology: Note that I said "slow down" rather than
"decelerate".  I'm becoming more and more convinced that
"deceleration" is a dirty word.  Any (any!) change in
velocity is an acceleration.  An acceleration in the
direction opposite to the velocity is still an acceleration;
it causes a decrease in speed.

This posting is the position of the writer, not that of Moe, Curly, or
Shemp.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.