Re: inertia demo

[Larry Woolf <larry.woolf@GAT.COM>]

John Denker mentioned the safety consideration of the pushed car.  It seems
that if students are all behind the car and some are pushing on the rear of
the car and one student is in the driver's seat, that is fairly safe
configuration.

An improvement on my originally posted item 2: Skip the bucket of rocks.
Just have one of your heavier students get on a racing bike and have another
students gently push the back of the student on the bike.  The student on
the bike does not pedal. Quite a bit of mass, low friction, no major safety
concerns.

This posting is the opinion of Larry, not Moe or Curley.

Larry Woolf;General Atomics;San Diego CA
92121;Ph:858-526-8575;FAX:858-526-8568; www.ga.com;www.sci-ed-ga.org

-----Original Message-----

From:  John S. Denker

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.

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.