How do momentum, impulse, and GPE factor into solving physics questions?

[ballaholic8]

Hey guys I am preparing for a physics contest and I am stuck with on a few questions. they are step by step questions. If someone can clearly explain how how to solve the following questions it would greatly help. Thank you.

 

[Doc Al]

Please show what you've done so far and point out where you are stuck.

 

[ballaholic8]

this is what I've got so far but I am not sure if its right.

thats what I've figured out so far but i need to verify this.

please help.