New answers tagged

-1

When you are walking you are doing work against gravity and friction. Consider this - when you walk on a flat surface, you shift your body weight on to say right leg. Lift the left leg and move it by a step. For the next step, you shift the weight on the left leg, lift the right leg and move forward. Thus you move. What is the work done? The leg consists ...


2

This sticker is indicating caution when you heat a liquid. Microwave can lead to superheater water which can be dangerous. If your water is superheated, it may not explode/boil over until an object is placed inside the water (e.g. a spoon). One way around this is to place a chop stick or object into the water while it is heating. This will prevent that ...


1

Heat transfer can occur by conduction, by convection, and by radiation. If you consider conduction through the bulk of the cup, the rate of heat transfer is directly proportional to the temperature difference across the material of the cup. As your experiment holds all variables equal except the temperature difference, cup A will lose heat at a faster rate ...


1

Pouring anything into the cup adds mass but doesn't add angular momentum. Conservation (plus friction between fluid and cinnamon) of angular momentum requires the new total mass to rotate slower than the original contents.


0

If we observe the path of the ball as radius reduces, we can see that the path followed is not circular. So between the radius and tangent, angle formed will not be 90 degrees.. This creates a component of tension along the path of the ball thus increasing its velocity


2

Have them pull out their smart phone and open up Google maps and touch the icon to zoom to their current location. Remind them that what they just did is only made possible by satellites in orbit using clocks specially tuned according to general relativity to maintain accurate synchronization with clocks on the surface (i.e., in the smart phone). Welcome ...


20

Related to the Andrea di Biagio answer. Here is a typical flight path for the Beunos Aires-Auckland route. The distance is approximately 10,300 km by the shortest route along a sphere. Direct flights are offered by Air New Zealand and take 11h40m - an average speed of 882 km/h. Looking at the map you present, the distance from Auckland to Buenos Aires looks ...


9

You need three flat Earth theorists on different continents (or otherwise well separated) all in on a (video) conference call, and have them measure the azimuth and elevation angles of the sun at the same time. The set of angles that they report will be inconsistent with their locations being on a flat disk laid out as in the map in the question. This is a ...


3

If the sun is a disk (or sphere) that is a certain distance above the earth, close enough that you get it at different angles above the horizon depending on where you stand, then it has to look like a different size to different people. If it looks the same size, then you cannot explain that it's at a different height above the horizon. See this diagram: ...


11

Foucault Pendulum is a great example. The original purpose of this experiment was to prove that earth rotates relative to the stars and not the other way around, yet nevertheless it proves that the earth rotates in a way which contradicts the "flat earth" theorem. This experiment can be easily recreated at home, if you don't live close enough to equator.


5

If you believe that anyone lives on antarctica at all, or really anywhere south of the antarctic circle, then you can use the "midnight sun" effect, which should not happen in the flat earth theory (because the sun moves around the "antarctica ring" during northern winter). Surveillance cameras will also work for this, if eyewitness accounts are not ...


2

Try https://www.insecam.org/ .Take a flat map of earth and make them go to the cities and watch the light and the online clocks. Nothing but a sphere fits the data. If the sun is going around a disk there would be night almost simultaneously over the flat disk, whereas the cameras will show progressive changes and night for half of their flat earth.


3

Take an arrow which you put tangent to the earth (assume it to be a perfect sphere). Now, travel around in such a way that 1) you enclose some finite area, 2) do not rotate the arrow locally. Coming back to your starting point you will notice the following: Although you did not rotate your arrow locally, you will end up with an arrow which is rotated ...


5

Can you convince your friend that time zones are for real? If he will believe that it is nighttime in China when it is daytime in the US, then his disk theory can't be correct.


6

Airplanes. Note that dozens of flights cross every ocean and the equator in all directions every day. If the Earth were a disk, it would actually be impossible to do that. For example, if the border of the disk were more or less where the borders of a planisphere are, it would be impossible to cross the Pacific. How would your friend explain how flights ...


27

I live close to Lake Erie and often see scenes like in this picture. Note that the bottom of the cargo ship cannot be seen due to the curvature of the Earth.


5

It is not about momentum. The total momentum is conserved: the fingernail flies in one direction, and you (plus the nail clipper) suffer a recoil to the opposite direction. The thing is that your piece of fingernail has a very small mass compared to your body mass, and the firing speed is actually not so high, so the recoil is negligible. About why the ...


0

According to a steam shower vendor, a 10KW unit is required to provide enough steam at 118 deg.F in a 6'x8'x 8' enclosure. The timer runs for 20 minutes (about right for a nice shower), so figure the unit would use 3.3KW and 2 gallons of water to make the steam room hot and steamy. According to numbers pulled from all over, figure an average 20 min shower ...


5

Consider that the specific heat of water is 4.147 kJ/kg. The specific heat of air is less than 1/4 of that, so for the air to heat you as much as the water, you would have to heat the air to a much higher temperature. That's one reason, along with conduction, that Arctic explorers say that water cools you 30 times faster than air. So it doesn't balance out. ...


2

So steam is caused when you have a supersaturated water vapor that cools and forms large suspended water droplets in the air. This is governed by the kelvin equation which you can read more about here: https://en.wikipedia.org/wiki/Kelvin_equation To get larger water droplets, or in your case a denser looking steam, you have two options: 1. you increase ...


-1

This is a side view in a high pressure area and low pressure area: The high pressure air flows outward from its center (moving from higher pressure to lower pressure) and to the ground, whereas the low pressure air flows towards its center (from low pressure air to even lower pressure air). The low pressure air forms clouds when it flows towards its ...


1

We don't harvest waste artificial light, because it would be ridiculously expensive to do so. The energy in sunlight is, at full sun, $1000W/m^2$. That's way higher than any artificial light in normal circumstances. So it's far more economic to position solar panels to optimise collection of daylight, rather than to capture artificial light at night. Any ...


2

There are two factors at play: the first is surface tension, which tends to generalize the action of forces across an area, instead of those forces localizing at one infinitismal point. Second, atmospheric pressure is still in effect. As gravity pulls on the liquid in the pipette, pressure in the bulb diminishes, so external atmospheric pressure pushes ...


0

If the pipette is long and thin, then the force of the liquid exerted by gravity is not enough to overcome the force exerted by the air as the liquid tries to fight its way out. Because of the short radius of the pipette, the fluid would have to travel very far to get out of the tube. If the pipette were short and fat, then the liquid has a much shorter ...


0

Your car consumes gas because of rolling resistance and air resistance. The first one scales with the total weight (at least approximately), the second one mainly with velocity squared. Furthermore, you accelerate with the car, and this energy consumption also scales with the weight. The amount of weight you save is $20/1285=1.6\%$. So the amount of money ...


0

Question: Gearboxes offer a significant benefit in that they affect the inertia ratio by a factor of the gearbox ratio squared. Answer: • Consider a motor running an inertia load JL via a mass-less, loss-less gearbox. The effective inertia (J) or its impedance (Z=sJ, where s is a complex variable), as seen through a gearbox of ratio G (where G > 1 for a car ...


0

Yes it is best to distribute any heat close to the windows even if its additional. If you place it next to a return air vent it will add heat to the whole system but only a portion will remain in the front room. I would not place anything (hot or cold) close to the thermostat because the set point will be satisfied to soon before the rest of the house has ...


1

Your central heating system doesn't work to keep the house warm: It works to keeps the thermostat warm. If the rest of the house gets warm too, that's just a side effect. If you put a portable electric heater under the thermostat, then the central heat won't have to come on because the electric heater will keep the thermostat plenty warm. But, that ...


5

There are several factors that may be taken in account, but the more important is the energy used deforming the tire. Suppose a deflated tire. As you move forward and the tire rotates, the part of the tire that is starting to touch the ground has to be deformed (since the tire is flat). You have to use an important amount of energy for that. Note that the ...



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