Hello, and welcome to our physics forum. I am not sure what exactly is confusing you, but are you aware of any potential equations that can be used to connect your known data with what the question is asking for? It will also be very useful if you try to understand the problem well and draw a relevant diagram with two states: the initial and the final.

I hope this helps. If you have any further questions don't hesitate to post them here! I would be happy to answer them for you!

@Prof.Smith Thank you so much professor Smith. Now, I can understand very well the solution. I have to say that although the problem was initially looking simple, it was actually very tricky!

Note that if you use g=9.8 m/s^2 you get x=20.4m and u=0.4m/s.

Hello, and welcome to our physics forum. I am not sure what exactly is confusing you, but are you aware of any potential equations that can be used to connect your known data with what the question is asking for? It will also be very useful if you try to understand the problem well and draw a relevant diagram with two states: the initial and the final.

I hope this helps. If you have any further questions don't hesitate to post them here! I would be happy to answer them for you!