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HNQ
1:17 AM
3
Q: Why do little chips break off so easily from strong neodymium magnets?

doetoeI have some strong toy neodymium magnets. Typically after a while little chips start breaking off, unlike from most other small metal objects, like in this image. It could of course be that neodymium is more brittle than metals used for other objects, or that they often hit each other much harde...

 
HNQ
1:43 AM
2
Q: Why does lemon sink in diet cola?

usr-local-ΕΨΗΕΛΩΝI have made a funny homemade experiment, repeatable, and with a high success rate over 6 bottles of cola. I haven't found any trace on internet. It reminds me the Mentos-Diet Coke experiment, but I am focusing on the lemon. Take a bottle of sugarfree cola, e.g. diet Pepsi in this case. Cut a lemo...

 
 
9 hours later…
HNQ
10:39 AM
1
Q: Why doesn't this way of calculating the moment of inertia of a sphere work?

user2714980Instead of the usual approach of integrating a bunch of discs, I do it differently. I integrate by subdividing the sphere into a bunch of concentric spheres containing mass on their surface. The integral becomes: $\int_0^R r^2 \cdot (4\pi r^2) \cdot \rho \space dr$ which ends up equaling $\frac{3...

 
 
4 hours later…
HNQ
2:27 PM
5
Q: How can a simple physical situation give rise to two different possible outcomes?

Tanisha DaharwalThe Question: An object of mass $5\, \mathrm{kg}$ is projected with a velocity $20\, \mathrm{ms}^{-1}$ at an angle $60^{\circ}$, to the horizontal. At the highest point of its path, the projectile explodes and breaks up into two fragments of masses $1\, \mathrm{kg}$ and $4\, \mathrm{kg}$. The fr...

3
Q: Regarding distance laws of gravity from “A Brief History of Time” and why the Earth doesn't fall into the Sun

mahacoderIn “A Brief History of Time”, Hawking explains Newtonian gravity in Chapter 2, Space and Time. The further apart the bodies are, the smaller the force. The gravitational attraction of a star is exactly one quarter that of a similar star at half the distance. This is because as we know, gravitatio...

 
 
3 hours later…
HNQ
5:49 PM
3
Q: Why do we feel weightlessness in water but not on land?

Shirsak MajumderWhen we draw a Newtonian free body diagram of a man standing still on land, we draw force g and the reaction force. In water when floating still, we still have force g but we also have the reaction force and buoyant force. We are not accelerating in either case. So what makes us feel weightless i...

 
 
4 hours later…
HNQ
10:03 PM
1
Q: The faster you move, does it take more and more energy to increase your speed at the same rate?

PetroleumJelliffeI'd like to confirm this somewhat counterintuitive result. Starting with the definition of kinetic energy: $$E = \frac{1}{2} mv^2$$ Assume a vacuum, no external forces, and starting from rest. Adding some energy $E$ to the system by burning some fuel (by firing a rocket, etc.), the following sho...

 
 
2 hours later…
HNQ
11:44 PM
3
Q: How is data transferred between devices?

Adm KuznetsovIf you send a text from your phone to your friend, do electrons move from your phone to your friend's phone? How is text transferred (physics wise)? I am a programmer and I want to know how it is working.

 

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