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**Newton's Law of Motion problem!!!! Help please!**

## Homework Statement

A small block of mass m1 is placed on block 2 of mass m2 this is then placed on the table. A string connecting block 2 to a hanging mass M passes over a pulley attached to one end of the table. The mass and friction of the pulley are negligible. The coefficients of friction between block 1 and 2 and block one and the tabletop are nonzero and are:

Coeff. between 1 & 2:

Static = (mus1) <-- mu sub static 1

Kinetic = (muk1) <-- mu sub kinetic 1

Coeff. between 2 & Table:

Static = (mus2)

Kinetic = (muk2)

## Homework Equations

c) M is large enough that the hanging blocks descend when the block is released. Assume that blocks 1 and 2 are moving as a unit (no slippage) Determine the magnitude a of the acceleration.

d) Now suppose that M is large enough that as the hanging block desends, block 1 is slipping on block 2

Determine the following:

i. The magnitude a1 of the acceleration of block 1

ii. The magnitude a2 of the acceleration of block 2

## The Attempt at a Solution

For c) I got:

a = g[M - (muk2)(m1 + m2)] / (m1 + m2 + M)

^^after factoring out g, correct?

Real concern is with d)

d) i. F = ma

fk1 = m1a1 = (muk1)n1

a1 = (muk1)m1g / m1

*m1 cancels out

a1 = (muk1)g

Is that right?

ii. was what confused me,

Should (ii) be the same answer as part (c)? Please help me on how to approach this if not. I am thinking that the reverse movement of m1 on m2 would decrease the acceleration, but I thought, as a system it shouldn't do anything because the friction on m1 is equal and opposite to m2. It isn't an external force. Help please?