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Why can engine performance be determined by “horsepower”? Is it some kind of conversion to real horses? What kind?
Horse power was introduced by James Watt to be able to approximate the power of the steam engine. Simply put, by determining the horsepower of a horse and comparing it to a steam engine, he could say: “My steam engine will replace 10 horses”. This way it was easy for everyone to imagine and was certainly well thought out in terms of marketing ...
Why is the selfie photo rotated horizontally?
All photos are basically rotated, more precisely inverted. This is because the display system of the camera/mobile phone has to create an actual image on the sensor. If we want to use a lens/mirror to create a real image, it will always be inverted. In the same way, the lens in our eye creates an inverted image on the retina and the brain “turns” it around ...
What food is the most radioactive?
I believe that the content of radioactive substances in food depends mainly on where we get the food from. Radioactive materials enter food from its surroundings. Plants and mushrooms get radioactivity from the soil they grow in and animals have radioactive particles in them either from food (plants) or air/water ...
What happens to lightning (energy) when it goes down a lightning rod to the ground?
In general, energy that we can’t use turns into heat and that’s what happens with lightning energy. It is necessary to realize that lightning is actually a slightly stronger example of an electric current (we call it an electric discharge) and therefore the same applies to it as, for example, to an electric kettle, a light bulb or a washing machine ...
Why is the colour of photos of the countryside different in the morning and in the evening (the sun has a similar angle)?
I don’t think that there would always be a difference between the photos in the morning and in the evening, I would rather expect that we can observe something similar from time to time. And I would guess especially in the summer ...
Does the force required to lift a stone in water vary with depth? E.g. Can I lift 100 kg at a depth of 1 m, 200 kg at a depth of 10 m?
Gravitational force acts on every body. If we want to lift a body, we must exert a greater force in the opposite direction. Buoyant force helps us in water — it has an upward direction and therefore if we want to lift a body in water, the sum of our buoyant force and our force must be greater than the force of gravity ...
Why don’t we see icy (blueish) and hot (reddish) air in different colours?
You may work on the assumption of infrared photos — they show the cool bodies in blue and the warmer ones in red ...
Our eye perceives only a (very small) part of electromagnetic waves and we call this part light. This wave is described by its frequency (in visible light, the frequency corresponds to a certain colour). The colour of the body depends on its temperature (if we are talking about light sources) ...
Why does a tsunami wave only go in one direction and not in all directions?
A tsunami wave, like other waves, spreads in all directions but the effects of a tsunami are observed only in certain places, so it may seem that the tsunami wave is moving in only one direction. Tsunami waves are caused by an underwater earthquake and the energy released by it is used to move a large mass of water ...
Why is it not possible to effectively predict earthquakes?
An earthquake is caused by a sudden release of mechanical stress between (or within) lithospheric plates. I’m not a geologist, but I believe this stress is caused by temperature differences and other phenomena that occur in and beneath these plates ...
Why does heat go up and cold air go down?
It is the same as why iron sinks to the bottom in water but wood rises. We probably all intuitively know that bodies with a high density in water sink to the bottom and bodies with a low density rise to the top. And perhaps we also know that if a body has the same density as water, it will stay in the given place — it will neither rise nor sink ...
Do mushrooms really contain heavy metals?
Yes, mushrooms, like other plants, contain elements that they draw into themselves from the surrounding soil. Compared to other plants, however, mushrooms can absorb a greater number of different elements ...
Is the same person’s weight different at the equator and at the North Pole?
I don’t want to be a quibbler but with this question, it is clear that it is good to use the right terms for what we want to find out. Because I could easily answer yes or no, and in both cases I would be right ...
How are high tide and low tide created and why are they needed or important on the Earth?
The high tide and associated low tide are caused by the gravitational force acted by the Earth and the Moon on each other. Thanks to this force, the Moon orbits around us and does not fly away. This gravitational effect is also responsible for the fact that the Moon does not rotate on its axis, so that it always faces us on the same side ...
How do “assemblies” which seem to never stop work (swing with balls knocking against each other, spiral water “overflow”, …)?
The mentioned “physics toys” represent an experimental verification of one of the basic laws of physics (and nature) — the law of conservation of energy. Energy is actually stored work and we can store this work in various forms of energy (chemical, electrical, magnetic, mechanical, …). And these toys just transfer individual forms of energy into each other ...
What is the speed of thought? At what speed does the brain give the command to the big toe? How long does it take for the big toe to react?
I’m not a doctor but I’ll try to answer to the best of my knowledge and applications of physical phenomena. I will convert the term thought to the processing of information which is certainly a thought. Our body is (in my opinion) an evolution-improved machine with certain limits. These limits are mainly determined by our surroundings ...
Why is it better to ride a bike on the road with bigger wheels than with smaller ones?
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 ...
How much water evaporates in 1 hour from 1 m² of water at a temperature of 30 °C?
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 ...
Why can’t metal utensils be used in the microwave?
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 ...
Why and how does a rainbow form?
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 ...
What phenomenon explains that I have much more power with a pulley and I can pull a heavier object than when I lift it normally?
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 ...
