Communicating Vessels in a noninertial reference frame

[Idoke]

Hello all,
Should be a simple question (just started Physics 1 not long ago).
Here it is:
The thin, fluid filled glass tube is sitting on an accelerating cart.
As a result the level of the fluid rises as shown in the picture (attached) by D = 0.6 m.
The distance L is given. L = 0.2 m.
Acceleration due to gravity is assumed to be 10.
Question: What is the acceleration a?

I was told to use the law of communicating vessels (very little information in English is found online on this subject) and "the effective vector g" (no idea what that means).
Very flustered by this, any help or a nudge in the right direction is appreciated.
Thank you!

 

[tiny-tim]

Welcome to PF!

Hello Idoke! Welcome to PF!

The principle of equivalence means that a body with acceleration a can be regarded as stationary if fictional "gravity" of strength a is added.

So I think the "effective vector g" is the (vector) sum of the usual g (10 m/s) and this fictional gravity of a.

Calculate the direction of this effective vector, and then pretend that gravity is in that direction, and that the cart is stationary.

 

[Idoke]

Thanks a lot! that did the trick! I was getting so confused with pressures and other things.
You rock!