1. The problem statement, all variables and given/known data The problem relates to a water tank see link http://www.phys.unsw.edu.au/~jw/1131/IntroLS.pdf and scoll down a little! 2. Relevant equations 3. The attempt at a solution so I think to go about this problem I need to use a conservation of energy approach. ie ke(i) + gpe(i)= ke(f) + gpe(f) so... initially the tap is not realesed thererore there is no kinetic energy at this time if I add the element (h) height, I can say the system at this a t=0 has gpe = (M + m)g(h) Hence, (M+m)g(h) = 1/2mv^2 therefore, v^2 = (2(M+m)g(h))/m v= √ (2(M+m)g(h))/m (m/s) Is this approach correct. And I am assuming that the tank would keep on going in the -x direction as the surface is frictionless...correct? And can I introduce the element (h)? Or would I have to use calculus to find a solution? Any help is appreciated!