Why do people go to bed?

What common phrase is represented by the below lines

Easy going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Medium going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Tough going:
Weak, 'I can't do it, I'm staying!'
Tough, 'Let's get going.'

Can you move 2 matchsticks to form four equal sized squares.

It has five wheels, though often think four, You cannot use it without that one more, You can put things in it, you can strap things on top, You can't find it in the market, but you can still go shop. What is it?

Can you count the number of lines in the below picture?

The more of this there is, the less you see. What is it?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

What is the centre of gravity?

I am never scared but became petrified and can’t live in a house but would die to make one. What am I?

If you drop a 15 kg iron bar and a 5 kg bag of cotton from a height of 50 meters which will reach the ground first?