# All Questions

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### Ventilated supercavitation formula

My goal is to build a model SWATH ship that uses ventilated disk cavitators, similar to the Juliet Marine Systems Ghost. To do so I would like to be able to create a 3D plot of speed, cavitator radius ...
85 views

### Why won't the bulb light? [closed]

Here's what the marking scheme says: "Capacitor gets charged first and acts as an insulator/blocks current". However, electrons flow from negative to positive, so shouldn't the electrons ...
• 89
55 views

### Electric field definition

In my book it says that "electric field" is defined as the "force per unit charge". What does the "unit charge" mean? My initial thoughts was that it meant 1 Coulumb, but ...
• 89
76 views

### Different methods give different answers to the compression of spring [duplicate]

At first, I have to write down the scenario to represent my doubt properly. Scenario: An ideal massless spring with a force constant of $k$ is kept vertically on the floor. Then a mass $m$ is kept on ...
27 views

### If 2 substances have same heat capacity and the same amount of heat is supplied to both which one will show a greater rise in temprature? [closed]

My textebbok says a substance with greater specific heat capacity shows a greater rise in temprature but if both the substances have the same heat capacity wont they show the same rise in temprature ...
1 vote
43 views

### Buoyancy force vs object weight

If an object is floating (partially or fully), does the buoyancy force = the weight of the entire object? My confusion is, situation A: 100g object is 50% submerged and floating situation B: 100g ...
• 51
268 views

### How does Temperature of a system change if doing work on the environment? Can the temperature of the system increase?

I am just a bit confused about how to relate Temperature and work. If my system is doing work on the environment, could the temperature increase? I know that you can lower energy while raising entropy ...
150 views

### What is the full QED Lagrangian with physics units written out?

I wonder what the QED Lagrangian would look like if you carefully write out all units of the terms and make sure they are consistent. I think there is something missing about Coulomb. Can you write ...
• 1,397
28 views

### Spectroscopy features of noble gases

I notice that some people focus on the light spectroscopy of noble gases. What difference will the closed shell make? Are the noble gases simpler than other atoms when it comes to light-atom ...
• 1,495
31 views

### How does narrowing and splitting/branching of a pipe affect speed of liquid flow?

What happens to the speed of a liquid in a pipe that is one of several branches that a larger diameter pipe splits into? Here is a question in a practise booklet I want to answer: "A horizontal ...
1 vote
37 views

### Euler's equation of motion for rigid bodies rotating with one rotation axis not through the body's center of mass

this is my first question in this forum. Thanks for all the knowledge and support shared throughout the whole website! I have a body with rotations around 3 axes. I am looking for the external torques ...
• 11
1 vote
36 views

### Proof that Fermi level is constant throughout a system in thermal equilibrium

The explainations I saw: The one I was referring to in this question. I described why I find this explaination not satisfying in the question. Consider $2$ systems in contact. The rate of particles ...
• 300
33 views

### Understanding the concept of hole in semiconductor physics [duplicate]

I've studied the Kronig–Penney model and learned about the effective mass theory and I know that at the top of the valence band the effective mass of electrons are negative, this is just an ...
• 283
18 views

### Center of Mass calculation in configuration of $3$ pennies inscribing equilateral triangle [closed]

I'm working on a problem that is asking me to solve the moment of inertia about the center of mass of a $3$ penny system where the edge of each penny is touching the edge of the others and the ...
1 vote
40 views