Calculating Force to Accelerate Mass M Without Moving m1 and m2 - Newton's Laws

[thoff430]

Masses on a "car"

Homework Statement

Hey.. I don't know exactly how to get the solution for this one...

We assume there are no frictions at all and we only look at the masses M, m1 and m2 (rope etc are massless)

I want to know how much force do i have to give to push M in such a way that it accelerates so fast that m1 and m2 won't move related to M?

Homework Equations

Well... Newton is our friend ;)

The Attempt at a Solution

Maybe [PLAIN]http://img713.imageshack.us/img713/8880/fffpw.jpg ? But I am totally not sure about this...

 

[PhanthomJay]

Homework Statement

Hey.. I don't know exactly how to get the solution for this one...

We assume there are no frictions at all and we only look at the masses M, m1 and m2 (rope etc are massless)

I want to know how much force do i have to give to push M in such a way that it accelerates so fast that m1 and m2 won't move related to M?

Homework Equations

Well... Newton is our friend ;)

The Attempt at a Solution

Maybe [PLAIN]http://img713.imageshack.us/img713/8880/fffpw.jpg ? But I am totally not sure about this...

Neither am I, since I don't know where this equation comes from. Note that since there is no movement of the masses m1 and m2 with respect to M, then all masses must have the same acceleration in the x direction, and no acceleration in the y direction. Draw free body diagrams, identify the forces acting, and use Newton's 3 laws.