- #1

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## Homework Statement

The coefficient of friction between A and the table is μ

_{A}.

The coefficient of friction between A and B is μ

_{B}.

A, B, C and D all move with an acceleration of 2m/s^2 (A and B move to the left).

Find the force that the friction between the bodies apply on B.

Find the tension of the yarn that connects A and C.

Find the mass of D.

At a certain moment, the yarn which connects A and D is torn. Will A and B still move together? (

**Show with calculations)**

m

_{A}=1.4kg ,m

_{B}=0.6kg, m

_{C}=2kg, μ

_{A}=0.2, μ

_{B}=0.75, a=2m/s^2

*Both times the static and dynamic coefficients are equal.

## Homework Equations

F=ma

## The Attempt at a Solution

The last question is what I am stuck in, but I don't have the answers so I will show my calculations prior to that.

Forces on A and B: (I hope everything is clear)

m

_{B}g=6N so N

_{B}=6N, now we could see that according to ma=F, 1.2=F, so the force is 1.2N.

Now if we look at C we could see that 4=T

_{C}-20, T

_{C}=24N.

Now if we look at A we could see that: m

_{A}g=14N, so N

_{A}=20N.

Using ma=F: 2.8=T

_{D}-1.2-24-0.2*20 so 2.8=T

_{D}-29.2, T

_{D}=32N

Looking at D: 2m

_{D}=10m

_{D}-T

_{D}, m

_{D}=4kg.

Now I am not sure what to do, I tried to draw the forces again, but from there I don't really know what to do. How can I know if C moves now? If it doesn't then A and B doesn't move, but if it does I don't know how to reach the answer.

Thanks in advance!