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What is the minimal wind speed necessary to blow away a paper lying on a flat table?

When you illuminate your fingers with a very intense light in order to see through them, you should notice that you can see individual vessels but the rest seems rather homogeneous. Explain why the vessels are visible but bones are not.

Design a lightsaber that looks and works in a similar way as the ones from Star Wars movies but using only knowledge and technology available to us.

Find out experimentally at least three different physical properties of gummy bears candy. You should explore even how do these properties depend on the candy's color. Some possible properties you can measure are melting temperature, Young's modulus, maximal tension, absorbency (change in volume or mass after being in water for certain amount of time), density, conductivity, index of refraction, solubility, dependence of any of the preceding properties on temperature or anything else you can think of.

How long does it take before the Sun rises and sets as seen from an air-plane that flies in the ecliptic plane? In the same situation how long is a day? What about night? Necessary information like typical height at which air-planes fly can be surely found on the Internet. Answer these questions for an air-plane flying both east and west.

Think of as many ways to verify that the Earth is spherical as you can. If you do verify this statement find a way to measure the radius of the Earth.

How much water can be taken out of a swimming pool (in one trial) using only your hair (assume you have a lot of them)?

Determine the maximum height a typical egg can fall from without breaking itself. How does the result change if you wrap the egg in some protective material which is not thicker than 5$\;\mathrm{mm}?$ Try couple of different materials.

• Dr. Nec.

There are two ways to measure the amount of wood in a pile of trees. Either as the volume of pure wood in the pile or as the volume of wood together with the empty spaces in the pile. Find the conversion factor between these two units assuming the trees are cylinders of radius $r$ that are layed one on top of the others.

• Bubbles.

A spherical cap of radius $r$ is made by blowing air into a circular surface of soap water. Estimate the velocity of air molecules hitting the surface?

• Jakub's breakfast

Every morning Jakub enjoys his favourite cereals which he pours into a bowl of milk. Assume the bowl is of circulur frustum shape with upper and lower radius $R$ and $r$ respectively ($R$ \geq r$)$, that the cereals are little solid spheres and that before he puts the cereals into the bowl there is milk of height $h$. What is the maximum amount of cereals he can fit into the bowl? You also know that the fraction of volume the cereals occupy inside a fully filled box is $\kappa$.

• Magnetic monopole

Let's have a metal plate magnetized in such a way that the upper and lower sides are the north and south poles respectively. We use these plates to create two semispheres with the outer side being the north pole. Now, if we glue these two semispheres together, we effectively get a magnetic monopole, which, as we know, can not exist in our world. Where did we go wrong?