Twisting, bending, squashing, and stretching of these things happen thanks to forces. Once you squeeze one thing soft and stretchable, like a rubber ball, it changes form. If you stop compression, you’re taking the force away, and also the ball changes back once more. We are saying the ball is elastic, as a result of it goes back to its original form.

If you apply force to one thing stretchable, as an example by processing into gum, it changes form. If you blow double as laborious, it stretches double the maximum amount. Blow too laborious and it snaps. This basic rule of stretching is termed Hooke’s law, when the mortal Hooke.

Elastic things return to their original form, but not each object is like this. several things merely bend or snap once you push them with an excessive amount of force. we are saying they’re plastic, although they are product of metal or another material. Plastic suggests that things bend for good out of form once you push or pull them.

Pull back on a toy and also the force you employ stretches the elastic. This stores energy within it, referred to as mechanical energy. Once you forgoing, the elastic returns to its original form. The hold on energy should go somewhere—so it’s given to the stone, flinging it through the air.

Pinch your skin and forgoing, and it springs right back once more. This can be as a result of young skin is incredibly elastic. Older skin isn’t as elastic, that is why older folks have additional wrinkles. Antiwrinkle creams work by covering skin in sticky chemicals that stretch it tight. This makes wrinkles disappear a minimum of for a moment.

Rubber are often stretched to 3 times its length.

Hydrogels, the world’s stretchiest materials, are often force to twenty times their original length.


Mirror and reflection

Mirrors play throw and catch with light. They catch light from in front of them and throw it back the way it came. Mirrors are made from thin metal sheets inside glass, but many other surfaces reflect light as well. A smooth lake mirrors the sky above it, and you can often see your face in shiny shoes or a polished spoon.

Light rays stream in straight lines, so a flat and smooth (plane) mirror reflects things much as they are. The reflected image looks like the original because the incoming rays bounce back in parallel lines. However, a mirror that curves inward (concave) makes things look bigger, while one that curves outward (convex) can make them look smaller.

Mirrors reflect heat as well as light. Hot objects give off infrared radiation, which is like invisible, hot light. When infrared hits a mirror, it reflects straight back again. You can test this effect for yourself by wrapping some silver foil around your arm. It feels warm because your body heat is being reflected back.

Cats are like walking mirrors. They can see at night because they have special reflecting surfaces (miniature mirrors) behind their eyes. These catch incoming light and bounce it back out through their eyes again. The light passes through their eyes twice, and this gives them double the chance to see dim objects. That’s why a cat’s eyes shine at night or in dim light.

Some telescopes need giant mirrors, but if a mirror becomes too big, it bends and buckles.

To get around this, the biggest and best space telescopes use mirrors split into dozens of honeycomb-like segments. Bolted onto a framework, very close to one another, they work together like a single giant mirror.