Knowledge
Tools

   Double-click on any word that you do not understand in the text to get its meaning from Cambridge Online Dictionaries. To see the Greek translation of the word, select the option "Greek" and then double-click on the word again. To return to the Cambridge Online Dictionaries select the option "English".
Select Greek translation or English meaning.


Klackers



A "Klacker" is a handle with two balls -- a red one and a yellow one in our toy -- that can move around as shown below on the right. Both balls weigh the same.

On Earth, you can make one of the balls (say the yellow one) revolve around the handle with a flick of the hand and hit the stationary ball (the red one). On impact, the yellow ball stops and the red ball revolves around the handle. When the red ball has gone around the handle, the process repeats itself. The red ball hits the yellow ball, which starts to revolve while the red ball stops.
What's happening? While the balls move around the handle, they possess momentum. A stationary ball has no momentum. When the moving ball hits the stationary ball, it passes its momentum to the stationary one.
Result: the formerly moving ball stops (i.e., it loses its momentum) and the formerly stationary ball moves (i.e., it gains the momentum).
When astronaut Mario Runco tried to use the Klackers in Earth orbit, he couldn't make them work as on Earth.
Aboard the space shuttle, the yellow ball would hit the stationary red ball, causing the red ball to revolve around the handle. But the yellow ball just slowed down. It did not come to a complete stop.
Eventually the faster moving red ball caught up with the yellow ball and hit it. Now the yellow ball moved faster, caught up with the red ball, and hit it.

Check that you understand what these words mean in this document
To weigh: to have a certain heaviness.
Impact: strong contact.
To revolve: to turn on or around an axis or a centre.
Momentum: an impelling force or strength.
Stationary: standing still.
Formerly: previously.