variable mass system

bhaiya.. can u solve that problem... ive two or three doubts in that:

(i) sand falls in forward direction .. but what direction is initial velocity of trolley?
(ii) find the time after which it stops ... it refers to the trolley right bhaiya? clarification ke baad i will try..

The only thing that I find useful to remember, while solving problems of variable mass systems is that, The Force is given as:-

F = d(mv)/dt= m(dv/dt) + v(dm/dt)
unlike F=m(dv/dt) of xconstant mass systems.

but will the trolley stop instantaneously or forever at that time... im thinking instantaneously... is it correct bhaiyya?