Why is the Hole below a Lock?

I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

My grandson is about as many days as my son in weeks, and my grandson is as many months as I am in years. My grandson, my son and I together are 120 years. Can you tell me my age in years ?

Count The number of F's in the paragraph below:

"FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS"

What goes up but never comes down?

John Went to the nearby store in a Mall to buy something for her home. Below is the conversation between the two:

John: How much for the one?
Shopkeeper: It is $2
John: How much for the Eleven?
Shopkeeper: It is $4
John: How much for the Hundred?
Shopkeeper: It is $6.

What is John buying?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

It was a dark stormy night and a couple were in a car driving madly to a city. The car broke down and the husband had to go get help from someone who spoke his language. He was afraid to leave his wife alone in the car so he locked the car before leaving. When he came back, the car was in the same state as he had left it but his wife was dead, there was blood on the floor and there was a stranger in the car. What happened?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?