8.3. That Stop Shot#
Now, we can go back to the incomplete example of that pesky stop-shot from Lesson 6 where we were left hanging.
Our embarrassment with the stop-shot was that Newton/Huygens momentum conservation could not uniquely predict the obvious observation of the beam-ball stopping dead while the target-ball shoots off when it’s struck. We can now fix that. Without emphasizing it then, now we have to assert that these billiard balls are perfectly elastic.
In this example, I solve that problem and billiard balls all over the world will go back to behaving the way that they should:
Please study Example 3:
If we’d used real billiard balls which are made up of molecular parts, then kinetic energy would not have been conserved. Energy would have been lost and a large part of it would come from the sound creation by their quick compression and release. You hear that collision. But all of the above discussion had “lost” kinetic energy becoming heat. And Mr Joule determined that heat was just another form of energy. So now we’re on to something.