Question

A force scale is attached to a stack of books lying on a flat table.
1.What happens to the size of the static frictional force as you begin to pull on the force scale?
2.What happens to the stack of the books if the applied force exceeds the maximum static frictional force?
3.What is the minimum size for the static frictional force, and under what conditions will the minimum static frictional force be observed?
4.What type of friction acts when the books are at rest but a force is exerted?

Answer 1

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Answer 2

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Answer 3

@Newton1 aha! you changed the question! ^_^

1) Remember that the equation for the force of static friction is actually the maximum amount of static friction possible
\[ F_{static} = \mu_s N\]
where mu_s is the coefficient of static friction, and N is the normal force of the stack of books. Any force that is less than that amount will do nothing to the stack of force, so as you start pulling, the force measured increases while the books stay stationary.

2) For this, remember that the coefficient of kinetic friction is always smaller than the coefficient of static friction, so when the force exceeds the static friction, the force of kinetic friction is much less, and the books get a a nice push start in the direction of the force!

3) The minimum size of the static frictional force is any value F>0

$) it's what all of these questions have been asking about!