May i know what formulas i'l be using with this newton's law problem

Question

The two masses are each initially 1.80m above the ground, and the mass less frictionless pulley is 4.8m above the ground. What maximum height does the lighter object reach after the system is released?

[Hint: First determine the acceleration of the lighter mass and then its velocity at the moment the heavier one hits the ground. This is its “launch” speed. Assume it doesn’t hit the pulley.]

Answer 1

the heavier object is pulled down, until it can go no further. (aka hits the ground) that means the heavy object falls 1.8 meters. pulling the ligher object up 1.8 meters.after that the lighter object is no longer accelerated.

the downward acceleration of the heavy object = the upward accelration of the lighter object.

so you determine its upward accelration, use the formula to calculate the speed of a falling object. v= 0.5g*t²