How to find the coefficient of static friction.

AI Thread Summary
To find the coefficient of static friction, a force diagram is essential to understand the forces acting on the book against the wall. The equation for static friction, f = μ * n, where n is the normal force, is crucial for calculations. In this scenario, a 35-N horizontal push is required to hold a 1.2-kg book stationary, indicating that static friction is at play even without motion. The discussion highlights the importance of recognizing equilibrium in the system, where friction balances the applied force. Understanding these concepts allows for the calculation of the coefficient of static friction effectively.
mateye10
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Homework Statement


In order to hold a book of mass m stationary against a wall, you must push horizontally with a force of at least P.
a. make a force diagram and find the coefficient of static friction
b. calculate the coefficient of static friction for the wall and book when at least a 35-N horizontal push is needed to hold a 1.2-kg book steadily at rest against the wall.


Homework Equations


F=ma
F_n=mg
F_f=μF_net

The Attempt at a Solution


I find it difficult to grasp the concept that, somehow, there is still friction between the wall and the book even though there is no velocity. My best guess would be:

F_f = F_net so μ would have to equal 1. help would be greatly appreciated.
 
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If there is no velocity and no acceleration, the system is in equilibrium. Try drawing the force diagram without the static friction and then you'll see how friction plays a role.
 
so is friction equal to weight?
 
Yes, and knowing that and the basic equation of static friction (f=μ*n), you can now calculate μ.
 
great, I see. thank you so much.
 

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