Static Friction: Phone Books & Wood Blocks

[cragar]

when you take 2 phone books , and inter-lay them page by page , so it makes them hard to pull apart . is this because it is like sliding a block of wood on a table just now you have like 1000 surfaces sliding on each other , is that what is going on .

 

[Doc Al]

is this because it is like sliding a block of wood on a table just now you have like 1000 surfaces sliding on each other , is that what is going on .

Exactly right.

 

[kjl]

I would also hypothesize that since interleaving the pages spreads the pages out (i.e., the front and back covers are further away from the middle pages than they would be if not interleaved), that attempting to pull the books apart tends to compress the pages in the middle, increasing the normal force (and thus the static friction). Thus, the harder you pull, the stronger the maximum force of static friction on each page->page contact, especially at the middle pages.

 

[rcgldr]

The OP had it right, all 1000 surfaces experience the same compressive force (per unit area), so the total friction is large.

 

[cragar]

thanks for your responses , just wanted to make sure what was going on .