physics gifs

If you dropped a water balloon on a bed of nails, you’d expect it to burst spectacularly. And you’d be right – some of the time. Under the right conditions, though, you’d see what a high-speed camera caught in the animation above: a pancake-shaped bounce with nary a leak. Physically, this is a scaled-up version of what happens to a water droplet when it hits a superhydrophobic surface. 

Water repellent superhydrophobic surfaces are covered in microscale roughness, much like a bed of tiny nails. When the balloon (or droplet) hits, it deforms into the gaps between posts. In the case of the water balloon, its rubbery exterior pulls back against that deformation. (For the droplet, the same effect is provided by surface tension.) That tension pulls the deformed parts of the balloon back up, causing the whole balloon to rebound off the nails in a pancake-like shape. For more, check out this video on the student balloon project or the original water droplet research. (Image credits: T. Hecksher et al., Y. Liu et al.; via The New York Times; submitted by Justin B.)

Why does a Popcorn pop?

Be it a movie theater or at the comforts of your couch, the popcorn is definitely a favorite snack among all age groups. But why does it pop?

Popcorn is no ordinary corn.

Of all the different types of corn out there, Popcorn is the only variety that pops, hence the name.

There is a tiny droplet of water inside the kernel of a popcorn, which is surrounded by a hard shell called a hull.

As the popcorn is heated, the water turns into steam. This builds pressure inside the kernel. When the pressure built cannot be contained by the hull, it POPS!

And a Popcorn is born.

For a popcorn to pop successfully, the ideal amount of moisture must be between 13- 14 percent.

When there is too little moisture, there will not be enough steam produced to carry out the popping and if there is too much moisture, the popcorn will crack prematurely.

Sometimes the most simpleton questions can have the most elegant answers. Ergo Stay Hungry, Stay Foolish!

Have a great one!

This is what happens when a carrot is fired at 300 km/hour at an egg, through two sheets of cardboard. 

This is what happens if you separate out the two sheets:

The egg survives! This shows how a Whipple shield works, and is what spacecraft use to protect themselves from micrometeoroid impacts in space. When the projectile (in this case a carrot, but in space it could be a speck of paint, a piece of an old satellite, or a bit of space rock) hits the first layer, it’s moving so fast that it starts to vaporise, because the energy of the collision is enough to break almost every bond in the substance.

It then sprays outwards, spreading the force of impact across a much wider area, meaning the second layer can stop it going any further, keeping your egg (or astronauts) safe.

Watch the full video on our YouTube channel.


Excitation of atom by photon

Electron excitation is the transfer of a bound electron to a more energetic, but still bound state. This can be done by photoexcitation (PE), where the electron absorbs a photon and gains all its energy or by electrical excitation (EE), where the electron receives energy from another, energetic electron.

When an excited electron falls back to a state of lower energy, it undergoes electron relaxation. This is accompanied by the emission of a photon (radiative relaxation) or by a transfer of energy to another particle. The energy released is equal to the difference in energy levels between the electron energy states.