<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>On Oct 13, 2017, at 8:49 AM, William Flynn Wallace <<a href="mailto:foozler83@gmail.com">foozler83@gmail.com</a>> wrote:</div><blockquote type="cite"><div><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Thu, Oct 12, 2017 at 8:56 PM, Mike Dougherty <span dir="ltr"><<a href="mailto:msd001@gmail.com" target="_blank">msd001@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><span class=""><div class="gmail_extra" dir="auto"><div class="gmail_quote">On Oct 12, 2017 7:45 PM, "William Flynn Wallace" <<a href="mailto:foozler83@gmail.com" target="_blank">foozler83@gmail.com</a>> wrote:<br type="attribution"><blockquote class="m_4833075520793438044quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div style="font-family:arial,helvetica,sans-serif;font-size:small;color:#000000"><br></div><div style="font-family:arial,helvetica,sans-serif;font-size:small;color:#000000"><br></div><div style="font-family:arial,helvetica,sans-serif;font-size:small;color:#000000">I also thought about something not in the book: why does a helium balloon rise? Don't tell l me it's lighter. My cat is lighter than I am and he is not flying around. The gas inside the balloon must be exerting pressure in every direction, so the force cannot be from there. Where is the force here??</div></div></blockquote></div></div><div dir="auto"><br></div></span><div dir="auto">Do you not know this or are you cleverly feigning to test the list for science blindness? </div></div></blockquote><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;color:rgb(0,0,0);display:inline">------------</div></div><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;color:rgb(0,0,0);display:inline">Ah, if only I were that clever. Even if I were, I'd not pull that on y'all. I just do not understand buoyancy. Another example from the book has a table pushing upwards against a book lying on it. Don't get that either. Don't see where the force is coming from.</div></div><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;color:rgb(0,0,0);display:inline"><br></div></div><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small;color:rgb(0,0,0);display:inline">Lighter things rise. I get that. I just don't see why.</div></div></div></div></div></div></blockquote><br><div>Buoyancy has to do with density of an object in a fluid medium. Your cat and you are not less dense than the air, hence (under everyday conditions) neither of you float away.</div><div><br></div><div>The book is pulled down by gravity (in classical mechanics). If it's being acted in by a force yet doesn't move (in an inertial frame*), then another force must must be balanced against gravity. Since the book doesn't move, then it must be acted on by an equal and opposing force. In this case the table itself is pushing up against gravity. (In fact, the book will warp the table slightly, though this is unnoticeable is most situations. But imagine a really heavy book if a table that's very flexible. By the way, I notice this with my bookshelves, which have sagged over the years.)</div><div><br></div><div>Anyone else, please correct me where I've gotten it wrong.</div><div><br></div><div><div style="line-height: normal;"><span style="line-height: 20px; background-color: rgba(255, 255, 255, 0);">Regards,</span></div><div style="line-height: normal;"><span style="line-height: 20px; background-color: rgba(255, 255, 255, 0);"><br></span></div><div><div style="line-height: normal;"><span style="line-height: 20px; background-color: rgba(255, 255, 255, 0);">Dan</span></div><div style="line-height: normal;"><span style="line-height: 20px; background-color: rgba(255, 255, 255, 0);"> Sample my latest Kindle book "Sand Trap":</span></div><div style="line-height: normal;"><font color="#000000" style="background-color: rgba(255, 255, 255, 0);"><a href="http://mybook.to/SandTrap" style="background-color: rgba(255, 255, 255, 0);">http://mybook.to/SandTrap</a></font></div></div></div><div style="line-height: normal;"><br></div><div style="line-height: normal;">* Well, it could move with constant velocity too, but the book is doing neither approximately if we take it to be in an inertial frame.</div></body></html>