What goes up but never comes down?

What does below rebus means ?

What is the centre of gravity?

Your last good ping-pong ball fell into a narrow metal pipe embedded one foot deep in concrete.
How can you get it out undamaged, if all the tools you have are your tennis paddle, shoe laces, and plastic water bottle, which does not fit into the pipe?

What jumps when it walks and sits when it stands?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

Count the number of times the letter "F" appears in the following paragraph:

FAY FRIED FIFTY POUNDS OF
SALTED FISH AND THREE POUNDS
OF DRY FENNEL FOR DINNER FOR
FORTY MEMBERS OF HER FATHER'S FAMILY.

I am a mother. However, I never give birth.

I am a father. However, I never nurse my children.

Wandering is not possible for me, but standing still happens occurs rarely.

Who am I?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

Can you write down eight eights so that they add up to one thousand?