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## Homework Statement

A 100 kg block rests as shown in Figure on a wedge of negligible weight. Knowing that

the coefficient of static friction is 0.25 at all surfaces of contact, determine: (g = 9.81 m/s2)

a) the angle θ (degree) for which sliding is impending and

b) compute the corresponding value of the normal force (N) exerted on the block by the vertical wall.

## Homework Equations

F=μN; ψ=arctanμ

## The Attempt at a Solution

This solution is given by my professor, as attached below.

My doubt is:

Why we can make an assumption that all the contact surfaces are in the condition of impending? It can happen that only the wedge is in the impending motion while others may haven't reached their maximum static friction yet. Thank you so much for your help and message me if you cannot get what I mean, I will try to elaborate more. Thank you!