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

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

John was piloting a plane behind a car but was never able to overtake it. Why?

I know there are two methods by using three time the same number with a plus(+) operator , you can make sum as 60.

One of them is 20+20+20.

whats the other way ?

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.

How many sides does a circle have?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

What is the Surname of Barbie Doll?