What has to be broken before you can use it?

I know a nine-letter word having only one vowel.
Do you ?

What breaks yet never falls, and what falls yet never breaks?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

A wooden log balances equally on the scales when weighed with three-quarters of a pound and three-quarters of a wooden log.

Can you calculate the weight of the entire wooden log?

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

My first is in chocolate but not in ham. My second is in cake and also in jam. My third at tea time is easily found. Altogether, this is a friend who is often around. What is it?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

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?