 ## Momentum Presentation File

```I don't see that the presentation addresses the type of elastic collision problem in which the masses are known, the initial velocities are known, but neither of the final velocities are known.  This would be the situation that Chapter Problems 66-71 ask students to solve.  Am I not seeing this in the presentation, or does it perhaps need to be added?
Thanks.```
`Wendy, this one is a little tricky, but shows the value of the relative velocity equation derived on slide 58 of the presentation.  This equation is mass independent.  If you use it for problems 66-71, you get an equation that shows the relationship of the two final velocities.  Not good yet - you have one equation, but two unknowns - the final velocities of the 2 objects.  But, then use the conservation of momentum, and you'll get another equation - and you have the same two unknown quantities - the final velocities of each object.  Simultaneous equations - two equations, two unknowns, which can then be solved.  Please give that a try, and if it still doesn't work, let us know and I'll scan in a solution and email it to you.`
`Thanks for addressing that John!  I created a slide that shows how to solve mass-known, but both final velocities-unknown for my class and they're good to go now.`
`I'm glad it was helpful!`
`1 Slide per page w/answers is unreadable. The solutions are on top of the multiple choice answers.`
`Thank you for alerting us to the issue. We have corrected it and a new version is now posted.`
```HI,
The PDFs are usually great but the words are crunched together in this presentation. We don't have the smart software so the pdf are all we use.
Thank you!!```
```Richard - thank you for alerting us to the issue. I have ran it through the PDF converter again and it is much better now. If you are working on a PC, you can download an older, free version of SMART Notebook if you would like by following the directions on this link:
```2020-02-24 version, slide 59, in the first eq, v2 is missing a prime.
`Thank you for pointing that out - it is now corrected.`