What you need:
- Tissues
- A pencil
- An empty toilet paper roll
- Rubber band
- Salt
What to do:
1. Place the tissue over one end of the cardboard cylinder and secure it with a rubber band.
2. Insert the rounded back of the pencil into the cylinders other end and push it through the tissue. Does the tissue tear easily?
3. Now, take another tissue and replace the torn one. Fasten it with the rubber band.
4. Set the toilet paper roll upright on a flat table. The side with the tissue should face down.
5. Pour salt into the cardboard roll until it is three-quarters full.
6. Tap the roll on the table to settle and pack in the salt.
7. Now, try to push the unsharpened end of the pencil through the salt to tear the tissue paper.
What happens:
In the absence of salt, the pencil tears the tissue paper easily. But once the roll is filled with salt, it becomes really hard to push through the tissue paper!
Why?
When you push the back of the pencil through the tissue, you apply force. This force is concentrated at the point where the pencil meets the tissue, and that’s where the tissue tears. Now, fast forward to the point where you are pushing the pencil through the salt to get to the tissue. The force you apply is distributed over many, many grains of salt.
And it also gets spread out over the entire area of the tissue paper instead of being concentrated at a point. This increased surface area of the tissue, thanks to the presence of salt, is what causes it to hold strong before your pencil.
Picture Credit : Google
