Answer:
1.27551m
Step-by-step explanation:
This is a simple energy convertion problem. Since there is no friction, and assuming no air drag and other external factors, mechanical energy should be conserved in this system.
Thus, we get:

We also know that the gravitational potential energy is equal to mgh, while the KE can be calculated using

One thing to note here, is that the final KE will be 0, as there is no velocity at the end. Furthermore, we also can set the initial PE as 0 as we are looking at relative height, and at the start it is at h=0.

Plugging in:

Solving for h, we get 1.27551m