jhobbie
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Does an object's kinetic energy increase, decrease, or stay constant when it reaches terminal velocity while falling?
9 votes

It stays the same, because it's dependent on the square of velocity. You're probably wondering where the extra energy goes because potential energy is falling. The answer is: it is dissipated into ...

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Dark energy vs. gravity
8 votes

The density of Dark Energy is not very high. In a place with lots of matter, the attractive forces of gravity are greater than the repulsive forces of dark energy. In mostly matter empty space, the ...

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Why does evaporation take place?
7 votes

Temperature is a measure of the average kinetic energy of particles, characterized by a Maxwell-Boltzmann distribution. Basically, that's a fancy way to say, if something is at 25°C, a large ...

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What would be the force constant for magnetic monopoles?
6 votes

Your new constant would probably be $k/c^2.$ $k$ is actually a simplified expression for $1/(4 \pi \varepsilon)$ which is the permittivity of free space. For magnetic fields, you use the permeability ...

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Isn't this statement regarding projectile motion wrong?
Accepted answer
5 votes

Note the vector signs! The vector signs mean that direction is included in the equation. So g only has a y component, but u may have components in any direction.

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Since cables carry electricity moving at the speed of light, why aren't computer networks much faster?
3 votes

How sure are you that electricity travels at the speed of light? Although electricity propagation moves at the speed of an E/M wave, and not electrons, its speed depends on the dielectric constant of ...

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What is the rebound angle of a circle striking a concave surface?
Accepted answer
2 votes

Depends on the size of the circles, but usually angle of incidence = angle of reflection (in this case to a line tangent to the circle at point of incidence).

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Expectation value and Dispersion of an Operator
Accepted answer
2 votes

Yes. There's an even easier notation for dispersion, or standard deviation which is $$D(Q) = \sqrt{ \langle Q^2\rangle - \langle Q\rangle^2 }$$ Both those terms are the same. So $D(Q)$ is zero.

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Understanding ket notation and the unitary matrix, what does a/the unitary matrix represent?
1 votes

Often times, an operation is something that changes the state of the system, like a measurement. But it can be other things that will change the state of the system.

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Can you explain Fermat's Principle to me?
1 votes

A simple explanation of Fermat's Principle is that you can approximate the path of the light by using the path that would take the least amount of time. For example if light is passing through only ...

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Is there a difference between "average acceleration" and centripetal acceleration?
1 votes

The problem with centripetal acceleration is that it is not a vector, and cannot possible have a negative sign. It should remain "constant" in this case, but its direction is changing. But actually, ...

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Is redshift a reliable means to know how fast an object is moving away or towards an observer?
1 votes

Wavelength doesn't change because of distance. However, because of Hubble's Law (Hubble's relation might be more accurate) the change does have a correlation with distance. It might help you if you ...

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Is the gradual progression of day(light) into night a clue that the earth is a sphere?
1 votes

Well, assuming a lot of things aren't true, then no. For example, if the Earth was shaped like a pizza, and the sun revolved around it, then it would have the same transition.

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"Weakness" of gravitational force
1 votes

You compare the size of the constants in the force law. For example $$F_g = \frac{GMm}{r^2},$$ and $$F_E = \frac{kQq}{r^2}.$$ In SI units $k= 9 x 10^9$, while $G = 6.67 x 10^{-11}$. That means to ...

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Confused about Newton's 3rd law
1 votes

To the first question: Newton's third law states that every force has an equal and opposite force. Thus, the force that Earth exerts on you with gravity (a big mass causing a huge acceleration on a ...

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What keeps objects made of the same plastic apart?
1 votes

They don't fuse because you haven't put in the energy to bond them together. Joining any two atoms takes energy, not just holding them in the same spot.

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What is the range of the validity of Coulomb's law?
0 votes

Well... you don't really measure electric/magnetic forces at distances much larger than several meters, but that's because electric potentials are difficult to build up. I guess on the small end, it's ...

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Why does a string remain taut in circular motion
0 votes

Are you aware that centripetal force is the net force on an object towards the center, and not a "real physical" force? It's simply an expression of other, more physical forces, such as tension, ...

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Doughnut magnet
0 votes

I guess this is the same question as "If you have two bar magnets and were able to somehow fuse the two south ends together, would you then have a magnetic monopole" or something. Magnetism on a ...

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Are we slightly lighter during the day and slightly heavier at night, owing to the force of the Sun's gravity?
0 votes

Well, at that point it's pretty small, right? And I guess maybe you could take into account gravity from all other "nearby" sources (i.e. the moon and maybe other planets). In fact, the most notable ...

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is boiling of water an isobaric process?
Accepted answer
0 votes

No it's not. Have you ever boiled water in a pot? The steam tries to escape because it creates too much pressure. It's just a simple matter of gases being less dense than liquids. As liquid water is ...

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Angular momentum for 3D harmonic oscillator in two different bases
-5 votes

Those three states you have listed are all equivalent. Think of those 3 state, and then realize that your choice of which is n1, which is n2, and which is n3 is totally arbitrary, Thus those states ...

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