# Get help with physics questions

Recent questions in Physics

### If all solid blocks have the same mass, which solid has the smallest density?

Ashley Fritz 2022-05-09

### Formula for the Bekenstein bound$S\le \frac{2\pi kRE}{\hslash c}$where $E$ is the total mass-energy. That seems to imply that the presence of a black hole in the region is dependent on an observer's frame of reference. Yet, my understanding is that the Bekenstein bound is the maximum entropy that any area can withstand before collapsing into a black hole.Does this mean that the existence of black holes is observer dependent? Or that even if an observer does not report a black hole in their frame, one is guaranteed to form there in the future?

Elle Weber 2022-05-09

### For a car that is accelerating linearly, the non-inertial frame of reference is the driver in the car where from his reference frame, the car is stationary. It is so called stationary because the non-inertial frame of reference has the same acceleration as the car. Is like the car's acceleration "transform" the driver frame of reference into a non-inertial. That's why in the non-inertial frame of reference, there is no force acting on the car.But when the car is driving in circles at a constant speed, in the non-inertial frame of reference there is a force acting on the car, which is the centripetal force. Why isn't this frame of reference like the above, not having the acceleration found in their each respective inertial reference frame? Why can't we have a non-inertial reference frame(due to rotation) whereby there is no centripetal force, subsequently eradicating the need for a centrifugal force?

Deshawn Cabrera 2022-05-09

### Area under Wien's displacement graphWhy does the area under Wien's displacement graph give Stefan-Boltzmann law for a black body?I couldn't find any proof of this. (I could just find this expression). I am not aware of the function of Wien's displacement graph as well (I just know that it is between Intensity and wavelength emitted by a black body).Is there a mathematical way to prove this?

bedblogi38am 2022-05-09

### Frequency and Wavelength peak for Wien's displaement law of a blackbody This is a question relating to Wien's displacement law for the Planck function. As we all know frequency and wavelength are related to the speed of light by:$\nu \lambda =c$However, why is it that:${\nu }_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}{\lambda }_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}\ne c$Any explanations would be very much appreciated.To all of the people wanting to know where this statement came from. It hasn't come from anywhere specific, is it a well known fact of the Planck function. ${\lambda }_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}=0.290{T}^{-1}$ cm K and ${\nu }_{\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}=5.88×{10}^{10}T$ Hz K${}^{-1}$

studovnaem4z6 2022-05-09

### Why is it hopeless to view differential geometry as the limit of a discrete geometry?Classical mechanics can be understood as the limit of relativistic mechanics $R{M}_{c}$ for $c\to \mathrm{\infty }$.Classical mechanics can be understood as the limit of quantum mechanics $Q{M}_{h}$ for $h\to 0$.As a limit of which discrete geometry ${\mathrm{\Gamma }}_{\lambda }$ can classical mechanics be understood for $\lambda \to 0$?

William Santiago 2022-05-09

### Fission producing Cs-137This is I suppose quite a precise question about Nuclear fission. What produces, aside from U-235, via a fission process, Cs-137?Does any isotope of Actinium, for example, undergo a fission process and break into Cs-137 and something else?Is there any way for me to easily figure this out for myself?Many thanks.

kazue72949lard 2022-05-09

### Why do only heavy radioactive elements perform fission?Why do only heavy radioactive elements perform fission? I mean what's so special about heavy elements which makes them ideal for nuclear fission?Also why do only neutrons show fission/fusion and why can't electrons preform fission/fusion?

bedblogi38am 2022-05-09

### Is electric potential energy responsible for energy release in nuclear fission and nuclear potential energy in fusion? What if elec. force not exist?It was my doubt and I thought it may be electric potential energy which is responsible for energy release in nuclear fission and by bombarding neutron we only provide energy to nucleons to cross equilibrium point (Felectric = Fnuclear) then it is spontaneous separated because of excess electric force, energy stored in electric field is released when it separates. Is it true? If yes then with this approach please explain why in lighter elements energy supplied is more than energy released in case of fission?

arbixerwoxottdrp1l 2022-05-09

### How can Wien's Displacement Law be 'changed' to a version for frequency?Wien's Displacement Law stated that for a blackbody emitting radiation,${\lambda }_{max}=\frac{1}{T}$where $T$ is the temperature of the body and ${\lambda }_{max}$ is the maximum wavelength of radiation emitted.Due to the relationship between wavelength, frequency and the speed of light, a value of maximum wavelength would give a value of minimum frequency, and vice versa.I then saw on the Wikipedia page for Wien's Displacement Law that${f}_{max}=\frac{\alpha {k}_{B}T}{h},$where $\alpha =2.82...$, ${k}_{B}$ is Boltzmann's Constant, $T$ is the temperature of the body and $h$ is Planck's Constant.How can this relationship for maximum frequency be shown?

britesoulusjhq 2022-05-09

### Radioactivity and nuclear fissionCan an unstable atom undergo both nuclear fission and radioactive decay?Other than the fact that that fission has to be initiated is there a difference between the final stability of the atoms?

Amappyaccon22j7e 2022-05-09

### What is half-life?

Jayla Faulkner 2022-05-09

### What are some common mistakes students make with exponential decay?

garcialdaria2zky1 2022-05-09

### Calculate the two longest wavelength of the Balmer series of triply ionized berillium (Z=4)

Jace Wright 2022-05-09

### If there were a light cone centered at some point P, and you were to look at that light cone from different reference frames, would it change its shape? I know that points inside and outside the light cone would remain inside/outside of the light cone in every frame, but does the light cone itself shift? If it does, how would it shift?

revistasbibxjm87 2022-05-09

### Imaging that the speed of that spacecraft is almost the speed of light "". But no acceleration. Meaning it's an inertial frame of reference right? Will you be able to throw a ball in the direction of movement? What about the direction inverse to the movement? Does that means that there is a direction of movement in an inertial frame of reference?

Logan Lamb 2022-05-09

### Is this possible to create a inertial frame of reference in the earth? How it is possible?

Hailee Stout 2022-05-09

### Does the wavelenth of matter waves depend upon the kinetic energy of the particle or object?Do the properties of the waves (wavelength,frequency) emitted by a particle or object depend upon the velocity, or as to say its kinetic energy? Is the De Broglie equation $E=h\nu$ applicable to matter waves as well?

rynosluv101wopds 2022-05-08