What is the centre of gravity?

What does a man do only once in his lifetime, but women do once a year after they are 29?

Before the start of the car race, John and Jacob have the same amount of fuel in their car. With this fuel, John can drive for 4 hours while Jacob can drive five hours.
After a time they realize that the amount of fuel left in John's car is 1/4th of the fuel in Jacob's.

For how long they are racing?

He does not have any heart but still, He manages to live.
If you kill him, you will eventually die but yet you kill him.
He cannot run, who is He?

In a family supper, a grandfather, a grandmother, two fathers, two mothers, four children, three grandchildren, one brother, two sisters, two sons, two daughters, one daughter-in-law, and one mother-in-law need to sit at a table.

There are only seven chairs available at the place. How many more chairs do they have to borrow so that everyone can sit down together for the suppers if everybody requires a separate chair?

Can you count the number of matches in the picture below ?

What is black when you buy it, red when you use it, and gray when you throw it away?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

If you say my name, I will no longer exist. What am I?

French Police inspects a room where there are no windows, no doors, no tables and is almost empty expect there is just a puddle of water. They found a dead man who obviously hung herself from the ceiling, but they are not able to figure out how this had happened.

John and Jacob entered the crime scene and easily able to solve the case.

How did the man die?