A rectangular container carrying liquid moves down an inclined plane, of inclination <img alt="\mathrm{30^{\circ}}" src="https://entrancecorner.oncodecogs.com/gif.latex?%5Cmathrm%7B30%5E%7B%5Ccirc%
A rectangular container carrying liquid moves down an inclined plane, of inclination with the horizontal, with a constant acceleration down the incline. The angle made by the free surface of the liquid with the incline is