Static Friction: Phone Books & Wood Blocks

In summary, interleaving two phone books page by page makes it difficult to pull them apart because it is like sliding a block of wood on a table with 1000 surfaces sliding on each other. This causes the pages in the middle to experience a higher normal force, resulting in a stronger maximum force of static friction. This is why it becomes harder to pull the books apart the harder you try.
  • #1
cragar
2,552
3
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 .
 
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  • #2
cragar said:
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.
 
  • #3
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.
 
  • #4
The OP had it right, all 1000 surfaces experience the same compressive force (per unit area), so the total friction is large.
 
  • #5
thanks for your responses , just wanted to make sure what was going on .
 

FAQ: Static Friction: Phone Books & Wood Blocks

What is static friction?

Static friction is the force that prevents two surfaces from moving against each other when they are in contact and at rest. It is caused by the microscopic irregularities and bumps on the surfaces that interlock with each other.

How is static friction different from kinetic friction?

Static friction is the force that keeps two surfaces at rest, while kinetic friction is the force that opposes the motion between two surfaces that are already in motion. In other words, static friction prevents movement, while kinetic friction slows down movement.

How does static friction work in phone books and wood blocks?

In phone books and wood blocks, static friction works by the two surfaces being in close contact and interlocking with each other. The weight of the phone book or wood block creates a normal force, which increases the friction force and prevents the objects from slipping or sliding against each other.

What factors affect the amount of static friction?

The amount of static friction is affected by the nature of the two surfaces in contact, the roughness or smoothness of the surfaces, and the amount of force pushing the surfaces together. Additionally, the surface area of contact and the angle at which the surfaces are in contact can also affect the amount of static friction.

How can we reduce static friction?

Static friction can be reduced by using lubricants such as oil or grease between the surfaces, increasing the surface area of contact, or smoothing out the surfaces. Additionally, reducing the weight or force pushing the surfaces together can also reduce static friction.

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