# All Questions

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### Why rocket equation? [closed]

while deriving rocket equation we find change in momentum of rocket and this is the result: $$Δp=MΔV+Ve ΔM$$ from here we divide this by time to calculate force and since no external force(freespace) ...
57 views

### If acceleration is a function of time like this $a=mt²$ where $m$ is constant. Then must be $v = a×t = mt³$ [closed]

Actually v is equal (at³)/3 by integration But why v can not be equal to at³
63 views

### Definitions of Thermodynamics and Holography

There are many differences between the laws of thermodynamics and the laws of black hole thermodynamics (BHT): Zeroth Law: In thermodynamics, the Zeroth Law establishes the notion of thermal ...
• 142
45 views

### Confusion between the contact force in string

My textbook says that when two bodies are in contact there exist a contact force between them and it has two components also one is perpendicular to the surface and the other is parallel to the ...
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• 91
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### Unique distribution of charge on a conductor

If i place some charge on a conductor then it will distribute itself in such a way that electric field everywhere inside is zero. My text book says that only one kind of such charge distribution is ...
• 311
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### My book states that contact force between two surface is equal to $\sqrt{N^2+F^2}$. where $N$ is the normal force and $F$ is the friction

Applied Force is our label for a contact force that a person exerts. When an applied force acts at an angle, it is actually a combination of two forces: normal and friction. The component of the ...
46 views

### Understanding Double slit and delayed choice experiment

I am having some trouble with two thought experiments, so I will list both of them below and I would be most grateful If somebody could explain to me what is actually going on or where I went wrong (...
69 views

### When we solve the Maxwell equations for $(\phi,{\bf A})$ in a gauge, will the solution $(\phi,{\bf A})$ automatically obey the gauge condition?

As the title of the question suggest; how you could determine if a gauge fixing is a condition or a requirement. Let me explain. Imagine you are working with Maxwell's Equations. By the definition of ...
• 1,203
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### What is a symmetry defect?

I found that it is a normal concept appearing in condensed matter physics and especially topological order field. I have been aware of the topological defect. But what is a symmetry defect? Could ...
39 views

### Confusion about energy transport in a circuit

I have some confusions about how to imagine energy flow in a circuit. Imagine for example just a simple circuit with a battery, two wires and a light bulb. According to classical Electrodynamics the ...
• 225
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### What are some ways to derive $\left( \boldsymbol{E}\cdot \boldsymbol{E} \right) \nabla =\frac{1}{2}\nabla \boldsymbol{E}^2$?

For each of the two reference books the constant equations are as follows:  \boldsymbol{E}\times \left( \nabla \times \boldsymbol{E} \right) =-\left( \boldsymbol{E}\cdot \nabla \right) \boldsymbol{E}...
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• 989
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### Struggling with physics homework, how do I find the acceleration of the system? [closed]

A 600 kg helicopter flies straight upward with a lift force of 12,000 N. A 150-kg spy named 007 hangs onto rope that is connected to the helocopter. A 50 kg physics student hangs onto a second rope ...