What does the below rebus riddle means?

What is the centre of gravity?

What common phrase is represented by the below lines

Easy going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Medium going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Tough going:
Weak, 'I can't do it, I'm staying!'
Tough, 'Let's get going.'

Can you find a five letter word that is left with only two letters if one is removed?

A girl is twice as old as her brother and half as old as her father. In 50 years, her brother will be half as old as his father. How old is the daughter now?

There are five vowels (a, e, i, o, u) in the English language.
Can you tell us a word that contains all these vowels?

What has 88 keys?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

I live in a bowl. I can swim. I have a tail. I also have fins and big eyes. What am I?