In my last post, I talked about one of the things I like most about my new Kindle – the eInk screen. And, as I’m finishing up reading a novel for the first time on it, I overall have really enjoyed the experience. However, one of the things I dislike about my Kindle is how slick it is. I found a video of the original Kindle’s Drop Test showing it apparently suriving a 30 inch fall, but I’ve read enough horror stories on the Amazon website to know I don’t want to actually put it to the test.

“Slickness” of an object has to do with the coefficient of friction. This relates to the static friction between two objects.  Static friction is the force that opposes motion from starting between two objects. This is influenced by what materials are in contact and the forces acting on the objects. In the case of a book (or Kindle for that matter), gravity is pulling objects down – if you totally let go of a book, it will fall. When holding a book,  the friction between your fingers and a book cover/pages creates an opposing force and prevents the book from sliding out from between your fingers.

Try this at home: place a paperback book flat on your hand. Now, slowly rotate your hand so that the book becomes more vertical. Depending on the book you chose and how dry your hand is, you should be able to get pretty close to near vertical before the book slips off.

When I read a book, I generally have two favorite grips: a one-handed prop from underneath where the book spine stradles my hand and a two handed grip, one hand on each side as in the picture below. Obviously, the grip under the book is very strong (providing the book isn’t too heavy), as my hand actively generates a force in opposition to the downward force of gravity. With the two-handed grip, I don’t have to worry about a book slipping through my fingers even in a relaxed grip because of the coefficient of friction.


With a Kindle, however, generally I use a one-handed side grip like the picture below due to where the “Next Page” button is located. But the Kindle has a very low coefficient of friction with my fingers and it feels like it is constantly about to slip through my hand. Apparently the original had a rubber backing – that would have been very nice to have, as rubber has a very high coefficient of friction! But, I now have a cover that holds my Kindle very nicely and has a good texture so I have a better grip.