What's the only room from which no one can enter or leave

Two friends were betting. One said to the other, "The coin will be flipped twenty times and each time the coin lands on the head, I will give you $2 and each time it lands on the tale, you will give me $3." After flipping the coin twenty times not a single penny was exchanged among them.

How many times did the coin land on heads?

How can one talk without saying a single word?

A rubber ball keeps on bouncing back to 2/3 of the height from which it is dropped. Can you calculate the fraction of its original height that the ball will bounce after it is dropped and it has bounced four times without any hindrance ?

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

A man was telling some of his war stories to his grandchildren.
"When the World War I was on the verge of end, I was awarded for my bravery for I had saved a group of my men." He coughed and then added, "When we were fighting in northern France, an enemy soldier threw a grenade at us. Before it could explode, I picked it up and threw it away. For my act of bravery, right before the war ended, A General gave me a sword engraved with the words "Awarded for Display of Bravery and Heroism in World War 1"."

Hearing this, one of the grandson spoke up. "Grandpa, this is not a true story. It can"t be true!"

The truth is that it was not. How did the grand children know it?

How can you write nineteen in a manner that if we take out one, it becomes twenty?

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

What can run but never walks, has a mouth but never talks, has a head but never weeps, has a bed but never sleeps?

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?