Different drag forces act against the movement of bodies, this situation is described as rolling drag. The size of the rolling drag depends on several quantities — the force that pushes the wheel on in our case, the riding surface, the radius of the wheel and the arm of the rolling drag. All these quantities describe how the wheel and the surface deform when interacting with each other ...

Unfortunately, there is no simple answer to such a simple question. The rate of evaporation of any substance depends on many factors and only a few are listed. Specifically, the rate of evaporation depends on the material (which in this case is water), temperature (entered), area (also entered), pressure and vapour suction ...

A microwave oven uses electromagnetic waves of a specific frequency for heating — 2.45 GHz. This frequency is not chosen randomly, it is the resonance frequency of water molecules. Resonance is an action in which we supply the oscillator (a body that oscillates) with such a frequency that its oscillation will continue to increase ...

The formation of a rainbow is one of the proofs that light is an (electromagnetic) wave. When the wave encounters an obstacle, it can bounce off or pass through the obstacle. In the case of passage into an obstacle (and exit from it), the direction of propagation of this wave changes. In physics, we call this phenomenon refraction ...

Although it may seem that a pulley (or an inclined plane or a lever) are special machines, using some strange aspect of physics, the opposite is true — these machines (we call them collectively simple machines) prove that everything works as it should and confirms the most basic principles of physics ...

The electromagnetic waves we use to make wireless calls are integral to our surroundings — and I’m not just talking about visible light. Electromagnetic waves of other frequencies, which we are unable to detect with our eyes, are coming at us from the entire Universe, most intensely from the Sun ...

Our eye has 2 types of light-sensitive cells — retinal rods and cones. While rods respond to less intense light but not to colours, cones are less sensitive to light intensity but respond to colours. That’s why we see the outlines of things when it is gloomy but not their colours. So we have to focus on the cones when it comes to colour perception ...

I like questions that I can always get right (or always wrong but I’m an optimist).The correct answer to such a question is yes and no. If I wanted to have only one correct answer, I would have to add to the question where the body falls ...

We probably intuitively know that there will be a difference when two small passenger cars collide and when a passenger car collides with a truck. It is obvious that the result of the collision is somehow related not only to the speed but also to the mass of both bodies. Therefore, we must include both the speed of both bodies and their mass in similar situations ...

The very alternation of day and night is caused by the rotation of the Earth around its axis. But that’s not the only movement the Earth makes, it also orbits the Sun. Orbiting around the Sun alone would not affect the length of the day, but the Earth’s axis is tilted (about 23°) relative to the Sun ...

It depends on what kind of fusion reaction you are trying to achieve in your garage device. If deuterium-tritium fusion is your goal, get a quality neutron detector and a long cable to run from the detector in the garage to your computer. Deuterium-tritium fusion generates very strong neutron fluxes. One successful fusion of deuterium with tritium produces one neutron ...

What the particles need for successful fusion is not so much temperature but speed. Only when they rush towards each other with sufficient speed can they overcome the electrostatic repulsive forces and get close enough for the nuclei of the atoms to fuse. But to have high speeds means to have high temperatures in the world of particles ...

I don’t think we have to worry about that. It is true that the deuterium required for thermonuclear fusion is obtained from seawater, but its consumption is very low compared to the volume of all the world’s oceans. It is estimated that a 1,000 MW fusion power plant could consume around 250 kilograms of deuterium per year. That is less than a kilogram of deuterium per day ...

From a cosmic point of view, it happens quite quickly, only a few tens of millions of years are enough. A star begins its life as a large ball of hydrogen that has condensed from a hydrogen cloud. In order for fusion reactions to occur, the hydrogen sphere must shrink enough to increase the pressure in its centre sufficiently ...

The success of the National Ignition Facility in an experiment on December 5, 2022, which released 3.15 MJ of energy in a fusion reaction using only 2.05 MJ of energy for the lasers required to ignite this reaction, is undoubtedly huge and a significant milestone in thermonuclear fusion research ...

No bucket of water will be big enough to extinguish the Sun. On the contrary, the more water you pour on the Sun, the more it will burn. The fire we normally encounter on the Earth, whether it is a campfire or a candle flame, is based on a chemical reaction ...

If matter was in direct contact with an object 150 million degrees hot, it would certainly not only melt, but also vaporize and immediately turn into plasma. But the extremely hot plasma core in the tokamak is not in such close contact with anything. The point is that it is effectively isolated from the tokamak chamber and the surrounding area by a layer of vacuum ...

Under terrestrial conditions, a spontaneous fusion reaction can never occur. Keeping the fusing fuel in a state where fusion can occur requires constant outside intervention. In the case of magnetic confinement, a proper magnetic fields to hold the plasma in place and heat the plasma to keep it at a sufficiently high temperatures are essential ...

The use of fusion reactions to power spacecraft is still pure speculation but in principle there would be two possibilities. The first option is that the electricity produced by the reactor would be used to operate some revolutionary, not yet discovered type of propulsion ...

There are many types of fusion reactions that release energy when the nuclei of light atoms fuse. Except for the different temperatures required for their ignition, they have different cross-sections and yields which are parameters that are crucial for the energy use of fusion ...