What is the name (and where to buy) the following object. Its one of
those objects where five or six balls are suspended by a string. The
balls hang in a row and when you pull on one it hits the others and
they go back and forth until they stop by themselves. They were
particularly popular in the 70's.
Thanks

Howdy tabletop39-ga,

These are commonly called "Newton's Cradle," "Balance Balls" and "Newton's
Pendulum" among other things.  The Office Playground website offers them.
http://www.officeplayground.com/newtonscradle3.html

"Newton's Cradle" by Donald Simanek goes into the Newtonian physics that
is behind them.  The page also has a nice animated image of one in action.
http://www.lhup.edu/~dsimanek/scenario/cradle.htm

"The apparatus usually consists of an odd number of identical steel balls
(7 is common) each suspended by a bifilar suspension from a sturdy frame."

A search on Google's Froogle shopping service provides more sources, and
units priced from $2.99 on up.
http://froogle.google.com/froogle?q=%22Newton%27s+Cradle%22

If you need any clarification, please feel free to ask.


Search strategy: Personal experience.

Froogle search as outlined above.

Looking Forward, denco-ga - Google Answers Researcher