What you need:
A straw
A friend
What to do:
1. Bend each end of the straw at a right angle to the centre so that the straw has an S-shape.
2. Pinch the bent ends of the straw shut and start twisting the straw in a pedalling motion.
3. Twist the straw until its whole length is compressed, until no more can be twisted.
4. Now ask your friend to flick the centre of this twisted straw hard, with her/his finger.
What happens:
The straw pops like a tiny cracker!
Why?
When you pinch the ends of the straw shut, you trap some air inside the straw. Winding the straw causes this air to be pushed into an increasingly small space.
There comes a point when you can’t wind the straw further. At this point, all the air is compressed into a small pocket at the centre of the straw. Here, the air pressure inside the straw is much higher than the air pressure outside because the trapped air is pushing really hard against the inner walls. When your friend hits this portion of the straw, it ruptures and you hear a ‘pop’ as all the trapped air rushes out.
Picture Credit : Google
