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

What does below chemistry rebus means?

I am a mother. However, I never give birth.

I am a father. However, I never nurse my children.

Wandering is not possible for me, but standing still happens occurs rarely.

Who am I?

An express train takes 3 seconds to enter the tunnel which is 1 km long.
If it is travelling at 120 km an hour, how long will it take to pass completely through the tunnel?

O_er_t_o_

Complete the missing letters of the given word.

In this image, you can see three almost identical Doraemon images. Can you spot the odd one out from them?

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

Christina is older than Kareena and Karishma. Katrina is older than Karishma and younger than Kareena. If Kareena has a brother named John, who is older than Christina, who's the youngest?

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

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?