# Questions tagged [homework-and-exercises]

Applies to questions of primarily educational value - not only questions that arise from actual homework assignments, but any question where it is preferable to guide the asker to the answer rather than giving it away outright. Please READ THE GUIDANCE IN META before asking homework-like questions.

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### How to find the lagrangian? [closed]

I'm having a hard time finding the lagrangian for this The system is on a table. All fours springs are the same. The rod has mass $m$ and length $2l$ and doesn't move on direction $y$. The ...
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### Block, pulley and an external force moving the whole system problem (classical physics)

I'm not sure in which blocks is $\vec{F}$ acting on, I know it is clearly acting on the block of mass $M$ and clearly acting on the block of mass $m_2$. I'm not certain about the effects of $\vec{F}$ ...
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### Heaters in parallel and series

I have a heater rated at 13 kW with two identical heating elements connected in parallel. If I connect elements in series instead what should be my expectation: That the total resistance in the ...
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### Null point for a infinite current carrying conductor [closed]

If a current carrying conductor of infinite length is placed along the magnetic meridian and current is flowing towards north pole, then is null point possible at any point in space?
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### Schmidt Decomposition : Writing it in this form

The beginning of this paper (pg.no. 1) on generalised Schmidt decomposition of three qubit states mentions the following: The Schmidt decomposition allows one to write any pure state of a ...
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### A mass attached to the end of a spring is pulled to a position $𝑥 = 𝑥_0$ [closed]

A mass attached to the end of a spring is pulled to a position $𝑥 = 𝑥_0$ and released from rest, so that it performs oscillations. The experiment is repeated, but now with the system immersed in a ...
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### Explanation Needed . Non conservative energy question [closed]

A planet of mass m is orbiting a star of mass $M (M \gg m)$. Initially (at $t = 0$), the planet has a circular orbit, i.e. $r$ is a constant and equals $r_0$. It then enters a region where the star's ...
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### Could someone tell me where I went wrong on this collision problem please? [closed]

Hi could someone please help me on this problem https://imgur.com/a/EQfo6zu I used the formula given, I think I have all the right values. I also plugged all of these numbers in and still got the ...
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### Effective weight of lifting 1 side of an object?

An employee at our warehouse lifted one side of a wooden pallet and dragged it $\sim 2$ meters and put it back down so that it was in a place that could be more easily picked up by a forklift. The ...
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### Is there any relation between the torque required to rotate shaft of the alternator and the load connected to it?

Suppose that a TV and a LED bulb both could be operated by the electricity generated by the alternator. In the initial phase the LED bulb is connected to the alternator and then it is replaced by the ...
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### What is the period of a ball rolling in a circle?

Imagine a uniform spherical ball of mass $m$ and radius $r$ rolling without slipping in a spherical bowl of radius $R$ with $r<<R$. There are two special cases of small amplitude oscillations: ...
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### Kaluza -Klein theory curvature [closed]

I calculated the curvature of the Kaluza-Klein theory according to 5D Ricci Curvature I couldn’t find the same answer to the above link. Did I do mistake in my calculation? Please check attached ...
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### How does earth's magnetic field trap charged particles?

I am very new here and I know this question is probably very basic for this place but I thought I would ask any way. I am in year 12 physics and this question is for a research paper that makes up a ...
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### Current induced in straight wire by a moving point charge [closed]

I have a straight wire that is grounded through a resistor. It initially has no current flowing through it. A point charge $q$ moves past the wire with velocity vector $v$ relative to the wire. How ...
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### Force exerted by a muscle [closed]

You have a forearm in a horizontal position and from the forearm you pull a muscle in a vertical position 4 cm from the elbow. The hand holds a weight of 6 kg at 44 cm from the elbow and the weight of ...
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### A person is in a room whose ceiling and two adjacent walls are mirrors. How many images are formed? [closed]

The answer is 7. But I observed that one pair of mirrors is parallel, so shouldn't the no. of images be infinite?
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### What is the Hamiltonian of this quantum system? [closed]

Quantum system with two disengaged degrees of freedom. The first one can be described with a monodimensional harmonic oscillator model and the second one with a rigid rotor model. What is the ...
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### How do I determine the flow rate in the picture below? [closed]

I´m a begginer in fluid dynamics. I need to determine the flowrate in the picture. My problem is that I don´t know how to determine the pressure at the begining of the Pitot tube. Oil of specific ...
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### Automatic hatch [closed]

I would like to calculate the torque of the motor that will drive the automatic hatch. This is the side view of the hatch. The closing and opening mechanism can be seen in the second to fourth ...