Solving Oscillatory Motion: When Block B Starts to Slip?

[Tzar_MacEng]

Homework Statement

The amplitude of the oscillation gradually increases till block B starts to slip. At what A does this happen?(there is no friction between the large block and the surface)

Homework Equations

Force equations etc... (F=ma) and

I reckon it has something to do with the force being combined with that a up there, but I have no clue where to start so that the mass of B cancels.

The Attempt at a Solution

No dice :(

I hope I've done everything right, I couldn't find an equation editor, so I just used office suit's one and upped the pics of it.

 

[alphysicist]

Hi Tzar_MacEng,

Homework Statement

The amplitude of the oscillation gradually increases till block B starts to slip. At what A does this happen?(there is no friction between the large block and the surface)

Homework Equations

Force equations etc... (F=ma) and


I reckon it has something to do with the force being combined with that a up there, but I have no clue where to start so that the mass of B cancels.

What force is responsible for accelerating the small block? Can you relate that force to the acceleration you have already found?

 

[Tzar_MacEng]

Well, I haven't exactly found an acceleration, however I imagine it is going to something related to F=ma and the mass will cancel somewhere through substitution and algebra. I just can't figure out where to start.

 

[alphysicist]

Well, I haven't exactly found an acceleration, however I imagine it is going to something related to F=ma and the mass will cancel somewhere through substitution and algebra. I just can't figure out where to start.

Think about the question I asked: what force is actually repsponsible for accelerating the small block? Once you have the answer to that, you will know which extra formulas you need, and it will also explain why there is a largest amplitude in the first place.

 

[Tzar_MacEng]

I figured it out