Conservation of Energy within a pulley system

[miamirulz29]

Homework Statement

Two objects are connected by a light string passing over a light frictionless pulley as shown in the figure. the 5.87 kg object is released from rest at a point 2.55m above the floor. The acceleration of gravity is 9.8 m/s^2. What is the speed of each object at the instant before the 5.87 kg object hits the floor. How much higher does the 3.24 kg object travel after the 5.87 kg object hits the floor.

Homework Equations

Ei = Ef

The Attempt at a Solution

The speed of the both objects are the same when both objects are moving. Because that is the case, I thought the answer would be v = sqrt(2gh), where h = 2.55m. However, that is not the case. Do I need to take into account the PE and KE of of the 3.24 kg object too?

 

[tiny-tim]

hi miamirulz29!

Do I need to take into account the PE and KE of of the 3.24 kg object too?

yup!

one mass on its own is not a closed system

conservation of energy (PE + KE = constant) only works for a closed system