Deriving a formula for atwoods Machine

[elvishtears]

Homework Statement

Figure 5-53 shows Atwood's machine, in which two containers are connected by a cord (of negligible mass) passing over a frictionless pulley (also of negligible mass). At time t = 0 container 1 has m1 and container 2 has mass m2 with m1 < m2, but container 1 is losing mass (through a leak) at the constant rate r. (a) At what rate is the magnitude of acceleration of the containers changing at time t? (b) When will container 2 reach maximum acceleration? Express your answers in terms of the variables given and g.

Just having trouble with this question, not sure where to go after obtaining

a = (m2 - m1)g/(m2 + m1)

 

[jbsteele]

Homework Equations Newton's 2nd law, F = maThe Attempt at a Solution From what I can see, the acceleration is changing at the rate that the two masses are changing. So the rate of acceleration would be equal to the rate of the mass change, r, divided by the total mass, (m2 + m1)? I'm really not sure how to approach this problem though.