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There are perhaps two questions here. The first is whether the planet is intrinsically dark, i.e. it reflects only a small fraction of the light that reaches it from the Sun and emits only a small ...
If you are accelerating while running on Earth, actually you are also accelerating Earth in the opposite direction. However for a given force, the acceleration is inversely proportional to mass, th...
No, going deeper into the moon would reduce gravity. This is covered by the shell theorem of gravity, proved by Newton centuries ago. If you have an evenly-distributed mass shaped as a hollow sph...
There seems to be some confusion about decibels here. "Decibel" stands for deci⋅Bel, meaning 10x of a Bel. A Bel is the log10 ratio of two powers, named for Alexander Graham Bell. Since a Bel is...
Inflation in cosmology refers to a phase of the early universe where the universe expanded extremely fast. And the universe expanding quite literally means the space getting bigger. As you noticed...
That is the number of downvotes you have cast, not the number you have received. Therefore, it means, that you have downvoted one other post.
I'm assuming that what's happening is that, for $t<t_0$, there's no gravitational field, then it's mysteriously instantaneously turned on at $t=t_0$. We can perform a Taylor expansion of $x$ ar...
Homework and exercises questions are generally allowed (currently anyway) under the Problems category, although there is the requirement that you need to 'show your working/attempted solution'. I d...
We don't need to, it just makes life easier (at least some of the time) As $\mathbf{k}$ is a 3D vector and $x$ a 4D vector, the answer doesn't appear quite as simple as 'Fourier Transforming makes...
A stuntman jumped from $1.25 \ \text{m}$ height and, landed at distance $10 \ \text{m}$. Find velocity when he jumped. (Take $\text{g}=10 \ ms^{-2}$) I had solved it following way. $$h=\fra...
It depends on what the failure was. Working the hinge could possibly make the little screw come loose quicker. This is the screw that acts as the shaft of the hinge. If the hinge actually broke,...
This looks like something the soldiers are being trained to do, or were trained to do. This means procedures were likely worked out that mitigate most bad effects most of the time. The top pictur...
In Srednicki's proof of the spin-statistics theorem for scalar fields ("Quantum Field Theory", section 4), he considers interaction terms, added to the free Hamiltonian, that are Hermitian function...
How do I deduce which setting suffices for mixing table salt + COLD tap water? Measure it. That really should have been obvious. My gut feel is that any reasonable agitation will work about equa...
When we launched this community, we did not yet have the ability to set different reputation grants for different categories. We've had this for a while but we failed to follow up before now, sorr...
There are a couple different types of indoor air humidifiers. Most notably, the naive steam humidifier with a heating element, and then ultrasonic humidifiers. Now, heating water to create steam o...
If you are already heating the space to maintain a constant temperature, and if both humidification methods result in the same eventual humidity, then the net energy used ends up the same. Any ene...
Basic answer It depends on what you care about. If you're primary concern is to minimize injury to the people in your car, then hold the brake firmly in ordinary low speed cases. This minimizes ...
When a pendulum made of a conducting material moves through a magnetic field, it's a well-established fact that it experiences a retarding force, thus slowing it down, however, I'm unable to unders...
I understand this is a chain of dubious assumptions, but I'm not sure exactly where I go wrong with this line of thought. Thanks to Hawking, we understand that black holes radiate particles. Howev...
I'm working on a problem involving a pulley system, and I’m confused about how the tension changes when forces are replaced by masses. Initially, if I apply forces of 20 N and 15 N directly at the...
All refractive lenses are approximations of the ideal. This is particularly the case of single-element lenses such as in eyeglasses. It so happens that the centers of such lenses are closer appro...
The center of thrust is effectively the weighted average of all the thrust locations. The weighting for each location is proportional to how much the thrust from that location contributes to the o...
Change in momentum is force times time. On the other hand, change in kinetic energy is force times distance (more accurately, the component of the force along the movement times distance; a force p...
Your analysis seems pretty good. To take an equivalent but more traditional example, imagine we throw a ball upwards. Ignoring air resistance and approximating the gravitational force as constant, ...
