(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Mass of 22kg on a 45^{o}to the horizontal.

[tex]\mu[/tex]_{s}= 0.78

[tex]\mu[/tex]_{k}= 0.65

Determine the magnitude of the largest force that can be applied upward parallel to the ramp to have the box remain at rest.

AND

Determine the magnitude of the smallest force applied to the top of the box, perpendicular to the ramp, to have the box remain at rest.

2. Relevant equations

All kinematic-based equations

Newton's Laws

F_{F}= [tex]\mu[/tex]F_{N}

3. The attempt at a solution

I assumed that the magnitude of the maximum force required would be equal to |F_{NET}| + |F_{F}| I got 2.0 x 10^{2}Newtons of force (correct to two significant digits).

However, the second part, I'm not quite sure of what to do. I thought that if you are applying a force perpendicular to the ramp, you would be increasing the force of gravity perpendicular to the ramp, and since |F_{N}| = |F_{gN}| the normal force would increase. Then I thought the absolute value of the force of friction would have to equal the absolute value of the force of gravity acting parallel to the ramp. In that case, just solve to find the force needed.

I was told I was wrong.

(*side note* I didn't find a use for the kinetic coefficient of friction. I assume that it will be useful, but can't think of how)

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# Homework Help: Friction: A box at rest on a slope

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