My solution for level 20 is quite easy and elegant. Just make an arch and connect the "U" with the right wall. Now push the ball on the arch and it should be very easy then to push it up the ramp and inside the "U".
Below you can see and alternative video solution, not so elegant :)
Physics Drop Level 20 Walkthrough, Solution, Cheats for Android, iPhone, iPad, iPod. Note: This is "Physics Drop" by "IDC Games"