Answer:
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
We are five little objects of an everyday sort, You will find us all in a tennis court.
What can be underwater, under fire, on fire and taking water all at the same time?
What two things can always see what the other sees, but can never see each other?
What is as big as you are and yet does not weight anything?
All about, but cannot be seen, Can be captured, cannot be held, No throat, but can be heard. Who am I?