This is something you can have your friends do and it will amaze them.
With the power of your mind, you can make someones arms magically raise up.
Have someone stand in-between a doorway. Then instruct them to extend arms from their waist to the door.
You want only the outside of their hand to be against door stop. Then have them push with all their might for about 30-60 seconds. Tell them this is to see how strong they are.
As soon as the time has elapsed, have them relax arms to the side and magically wave your hands in front of them. Their arms will begin to raise up!!!
This happens because of the muscles used when pushing against the door.