Falling of the box in the accelerationg train

1. May 12, 2010

ldv

1. The problem statement, all variables and given/known data

A cuboid of constant density, height h and length of bottom side=L is in the train. Determine the minimal necessary acceleration (of the train) needed for the cuboid to fall. There is no slipping.

(that's all that is stated in the text)

2. Relevant equations

not sure, probably the friction, and the inertial force

3. The attempt at a solution

I don't really know where to start, it will fall (backwards? =opposite to the direction of the acceleration) because of the inertial force? but there is also friction involved, since there is no slipping?, and this falling of the box is actually the rotation around the bottom side? and the force of inertia has to be greater than the force of friction?

please just some hint about what is going on in this situation!!!

2. May 12, 2010

tiny-tim

Welcome to PF!

Hi ldv! Welcome to PF!

Anything will start to tip if the reaction force reaches the edge of its support.

The question assumes that the box does not slip, but it will tip over backwards if the train accelerates fast enough.

Hint: in what direction and where is the force making the box accelerate? where is the normal reaction force?

take moments about the centre of mass of the box.