Kinda stuck, so I'd appreciate the steps.
How do you solve this Mechanics/friction question?
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$\begingroup$
algebra-precalculus
classical-mechanics
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0what did you try? – 2017-01-09
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0@ArnaldoNascimento I think I'm misunderstanding the 'weight' part in my diagram. Does weight go directly down to the ground, or is it at an angle, based on the surface? – 2017-01-09
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0take a look at my answer. Is that clear? – 2017-01-09
2 Answers
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Hint:
Here is how the forces will go. You have to make de decomposition of the weight $\overrightarrow{P}$ on the axis $x$ and $y$ in order to find the equilibrium.
In the $x$ direction you will have the friction force $\overrightarrow{Fr}$ and the part $\overrightarrow{P}\cdot \sin 28º$.
In the $y$ direction you will have the normal force $\overrightarrow{N}$ and the part $\overrightarrow{P}\cdot \cos 28º$.
Can you finish?
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You must consider the components of the weight:
- Normal component to the desk:
$$W_{\perp}=W\cos\alpha$$
- Parallel component to the desk:
$$W_{||}=W\sin\alpha$$
where $\alpha$ is the given angle.
So the frictional force is: $$F=0,6\cdot W_\perp=0,6\cdot 8N\cos28$$
Now you can also evaluate $W_{||}$ and see if $W_{||}\ge F$.

