# Conservation of Momentum

1. Jan 25, 2007

### Gregie666

hi.
can anyone push me in the right direction with the followin problem, please?

1. The problem statement, all variables and given/known data
a cart is moving on a frictionless surface at a speed of $$V_0$$
the mass of the cart is M.
it suddenly starts to rain at time t=0. the rain is dropping vertically at a rate of q gk per second.
the cart collects all the rain drops that hit it.
express the speed of the cart as a function of time passed since it started raining.

2. Relevant equations
$$F = {{dp} \over {dt}}$$

3. The attempt at a solution
$$& F = {{dp} \over {dt}} \Rightarrow \cr & 0 = {{dm} \over {dt}}v(t) + {{dv} \over {dt}}m(t) \Rightarrow \cr & 0 = qv(t) + {{dv} \over {dt}}(M + qt) \Rightarrow \cr & qv = - {{dv} \over {dt}}(M + qt) \Rightarrow \cr & qvdt = (M + qt)dv$$

so i get this equation and i dont know how to solve it for v...

**how do i add line breaks to the latex??**

Last edited: Jan 25, 2007
2. Jan 25, 2007

$$\int { \frac {q}{M+qt}} dt = \int {\frac {1}{v}}dv$$