What does this mathematical rebus means ?

Forwards I am heavy, backward I am not. What am I?

Why are all black people so quick ?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

Who is generally closer to the kids, mom or dad?

(it's a funny riddle)

How many bananas can you eat if your stomach is empty?

A quarter is one-fourth of a dollar but Mr. John has changed the equation as below :

DOLLAR * 4 = QUARTER

Can you replace each letter with a digit to make the above solution correct?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

How can a man go eight days without sleep?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?