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## Homework Statement

Boxes A and B are at rest on a conveyor belt that is initially at rest. The belt is suddenly started in an upward direction so that slipping occurs between the belt and the boxes. Knowing that the coefficients of kinetic friction between the belt and the boxes are ([tex]\mu[/tex]

_{k)A}= 0.30 and ([tex]\mu[/tex]

_{k)B}= 0.32, determine the initial acceleration of each box.

## Homework Equations

[tex]\Sigma[/tex]F = m * a

m = W / g

F

_{friction}=[tex]\mu[/tex]*N

**3. F.B.D.**

**4. The attempt at a solution**

Hello, again, wonderful people! It's me again with another dynamic problem; although this one is centered around Newtons' second law. I am afraid to admit that I am a bit unsure where to start this problem, as the dimensions of it confuse me. Boxes A and B are touching eachother, which begs me to ask the question...are there two normal forces on one or both of these boxes?

Also to sort of go with that, how would I orient the force normals? (If there are multiple?) I realize that the angle to use is 15, but I am unsure of using sin or cos. I have always assumed that if you're orienting an angle to the horizontal(x axis) you use cos, and if you're orienting an angle to the vertical (y - axis) you use sin, but I have witnessed that this is not the case.

Could someone please help me out with my questions...as well as giving me a sort've spurn in the right direction? Thank you!