acceleration and water height

[Swatch]

I'm having trouble with this problem here.

A U-shaped tube with a horizontal portion of lenght L contains a liquid. What is the difference in height between the liquid columns in the vertical arms if the tube has an acceleration toward the right?

There must be a net force to the left that presses the liquid to the left. In the right column there must be a pressure greater than the atmospheric pressure. But I don't know how to relate the lenght of the tube to the answer. Could someone please give me a clue how to solve this.

[mathmike]

why must there be a force to the left? acceleration is to the right. what makes you think that there is pressure greater than atm. on the right. could you explain your logic.

[Swatch]

The tube accelerates to the right. The water goes to the left, so there must be a force pressing it to the left. I know its not really a force, but It helps thinking of it that way. When you drive a car in a circle your body gets pressed to the sides. Your body is not in a an inertial frame of reference neither is the water. Is this not true?