Newtonian mechanics covers the discussion of the movement of classical bodies under the influence of forces by making use of Newton’s three laws. For more general discussion of energy, momentum conservation etc., use classical-mechanics, for Newton’s description of gravity, use newtonian-gravity.

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Deduction of Lagrange's equations for non-conservative systems using Hamilton's Principle

Consider $\vec{F}$, as the total force applied on the system, $U$ the potential energy of the existent field, and $\vec{Q}$ a non-conservative force. We have that: $$F_k=-\frac{\partial U}{\partial ...
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1answer
28 views

When applying the equation of torque and equating it to $I\alpha$ which moment of inertia do we take?

I believe $T=I_{cm}\alpha$, where $I_{cm}$ is the moment of inertia about centre of mass and $\alpha$ is the angular acceleration. But do we take $I_{cm}$ even if the torque has been taken about a ...
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4answers
56 views

Must one include friction and gravitational force in the work term?

Example problem: "A sled has an initial velocity up a ramp of 5 m/s, the ramp has an angle of 20 degrees to the horizontal, and the coefficient of dynamic friction between the sled and the plane ...
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2answers
71 views

Simple model that explain the flow of electrons in metals

I am not quite clear about how electrons (negative electric charges in general) flow through a metal. I imagine the metal as a lattice of small positive charges $+q$ that can not move and the - and + ...
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1answer
97 views

Bead on a smooth rotating rod

Suppose a bead ($m$) is free to move on a thin rod in the otherwise empty space. The rod is made to rotate at constant angular speed $\omega$. Lets assume the initial position of the bead is $(r_o, ...
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1answer
74 views

Accelerated pure rolling and friction

I know that if a body is pure rolling with no acceleration then friction acting on it is zero. But what about if the CM has an acceleration? Then can we say that friction is present? Suppose that ...
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0answers
13 views

About the movement of an electric charge forced to always stay on a circle [closed]

I do not know how to solve a problem like this: Find $r_B(t)$ knowing: $q_A$, $r_A(t)=r_A$ (the charge A can not move), $q_B$, $r_B(0)=r_{B0}$ and $v_B(0) = v_{B0}$, $q_B$ can move only on a circle ...
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1answer
91 views

Who told us how to measure torque?

We all know that force and torque are physical quantities which we have defined according to our purpose of work. Now we are all aware that Newton's Second Law from his Laws of Motion states how to ...
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2answers
41 views

System of potential energy

Is potential energy calculated between a system? More specifically, if we say 'potential energy of a ball with respect to earth', does it mean that the Earth + the ball is a system?
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2answers
71 views

Conservation of Mechanical Energy Before and After Impact of a Hammer

If a hammer does work by driving a nail into a wooden board, how does the mechanical energy from right before the hammer hits the nail compare to the mechanical energy after the nail has been driven ...
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0answers
109 views

Spherical pendulum simulation - numerical problems

I am trying to simulate a spherical pendulum. I have derived the equations of motion and they come out the same in the Newtonian approach or the Lagrangian way. However, I am running into problems ...
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1answer
123 views

How can one conclude upward force is related to tension in this question?

In preparation for the SAT Physics Subject Test, I have been doing extra practice problems. This one states: A garment bag hangs from a clothesline. The tension in the clothesline is $10 \,\text{N}$ ...
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1answer
42 views

Mismatch between underdamped and critically damped solutions

If you have a harmonic oscillator with damping $D$ (e.g. small angle pendulum) $$\ddot{\theta}+D\dot{\theta} + \theta=0$$ then the solution I get in the underdamped case ($D^2-4<0$) is: ...
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0answers
22 views

how to reduce the order of the hamiltonian equation for electrical problem given below?

I am having my FYP in this Hamiltonian project to analysis the integrator for Hamiltonian system. Can anyone please guide me how to reduce the equations to first order using substitution method?
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1answer
72 views

Why is it easier to pull a lawn roller rather than pushing it?

Does it have something to do with friction or weight distribution in pulling is favorable or anything else ?
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1answer
49 views

How do forces affect work? [closed]

I was doing my homework and I came across the question: Suppose that two objects, each with the same mass, are accelerated from rest to the same velocity. The force that accelerates one object ...
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1answer
55 views

How is this seemingly counterintuitive result in a rotation problem explained?

In the classic spool problem, where a spool of string of mass M is unrolled with a force F, like in the diagram, after working through the equations with Newton's laws of rotation and translation, we ...
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2answers
62 views

Magnitude of tension in a bent string

I understand tension in a straight string as a reaction force to a weight, which acts along the string, ultimately resulting from the attractive forces between the constituent particles of the string. ...
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2answers
77 views

Are some laws in physics really as simple as they seem?

For example, is $F = ma$ really an exact formula, or is it an approximation? I know a lot of formula's come from taking the first few terms of a Taylor expansion, so I was wondering if the simple ...
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1answer
132 views

Tension in string question [closed]

Problem: A 12.0-kg box resting on a horizontal, frictionless surface is attached to a 5.00-kg weight by a thin, light wire that passes without slippage over a frictionless pulley (the figure ...
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1answer
49 views

string applying a force on pulley

Why should string apply a force on pulley?(like atwood machine cases)and does that mean the pulley will exert an equal force on string(newton's third law)? Please explain in detail,if possible ...
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1answer
49 views

Please help me with this doubt from center of mass concept

Take the case of Atwood machine where masses of blocks are $m$ and $2m$. The acceleration of individual masses are $\frac g3$. now the acceleration of center of mass of masses and string system is ...
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3answers
73 views

Does an object decelerate when reaching terminal velocity

I'll take the sky diver example. Right when a sky diver jumps out of the plane the net force of the diver is greatest. Then the diver begins to reach terminal velocity where the force of resistance = ...
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1answer
55 views

Time spent in eclipse of an object

Well consider an orbit - I'm trying to calculate the exact time spent in the shadow of the body you orbit around. An explanation of "shadow" (sun is positioned to the far left): For a circular ...
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0answers
24 views

Roberval Balance [closed]

Is there any mathematical/mechanical article that explains in detail why the Roberval balance is taken place? I generally observed that the classical mechanisms are not analysed in detail, even in ...
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3answers
75 views

Why do objects move when you apply a force that's equal in magnitude to the friction? [duplicate]

If the friction on an object is 200 N and you apply 200 N, it seems, the forces should immediately cancel each other out since the friction and your applied force go in opposite directions, leaving ...
2
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1answer
59 views

Why is friction not dissipative in rolling motion? [duplicate]

We know that non-conservative forces like friction is a dissipative force. But according to my book when a solid cylinder is rolling down a rough inclined plane of inclination angle $\theta$ the ...
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3answers
114 views

What is the distance between two objects in space as a function of time, considering only the force of gravity? [duplicate]

What is the distance between two objects in space as a function of time, considering only the force of gravity? To be specific, there are no other objects to be considered and the objects in question ...
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1answer
52 views

Why does Goldstein's derivation of orbits from Newton's law not yield the orbit consisting of symmetric oscillation along a line thru center of Sun?

Why does Goldstein's derivation of Keplerian orbits from Newton's law of gravity not yield the orbit consisting of symmetric oscillation along a line passing thru the center of the Sun? The fact that ...
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5answers
160 views

Pushing down on the gas pedal of a car a good example of jerk?

I'm trying to think of the clearest examples to demonstrate the concept of jerk to a layman. Ignoring drag and making other reasonable assumptions (friction is conveniently there to only allow you to ...
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1answer
29 views

Conservation of momentum in inelastic conservation

Why does momentum and velocity change along contact normal but not contact tangent In in elastic collision? Suppose a ball strike an inelastic surface. It's velocity component does not change along ...
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2answers
54 views

Roller Coaster Physics

I am trying to figure out how to calculate the $g$-forces throughout a non-uniform corkscrew as well as the exiting velocity. Do you calculate each radius separately and each $g$-force separately ...
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2answers
129 views

Defining gravitational potential

I recently came across the definition of gravitational potential where ..... Suppose a particle of mass $m$ is taken from a point $A$ to $B$. Let $U(A)$ and $U(B)$ denote the gravitational ...
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1answer
89 views

Confused by gravity and weight [closed]

I know that $F = mg$ so $2,00 \textrm{ KG m} \cdot 9,81 \textrm{ N g} = 19,62 \textrm{ N F}$ Why does my book say that the weight of a $2,00 \textrm{ KG}$ object is $19,62\textrm{ N}$, the mass is ...
2
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2answers
87 views

Center of mass chaotic in n-body gravitational interactions?

I wrote a gravitational particle simulation. To prevent the particles flinging off out of the screen, I added a bit of friction (it also makes the animation prettier as particles spiral into one ...
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2answers
36 views

Effect of a cushion on the average force felt

I had a question about how a sitting on a cushioned surface, like on a couch etc. affects the average force felt by a person vs. sitting on a hard surface. I understand that stopping an object using a ...
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2answers
62 views

Rotation of a system of two masses [closed]

A uniform disc of mass M and radius R is suspended vertically by a pivot at its periphery. A particle of mass M is fixed to the rim and raised to the highest point above its center. The system is ...
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1answer
40 views

How to explain the motion of these pendulums? [duplicate]

Got very interested recently in a video I saw running thru my feed: https://www.facebook.com/PortalAECweb/videos/913996365374257/ Well, I got very intrigued about the physics of it and wanted to ...
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1answer
14 views

What maximum height of a 1 ton car when driven with 2500 kcal? [closed]

It is recommended that humans ingest, daily, around 2500 kcal. If this energy could be used to raise a car with a mass of 1 ton, from the ground, how high the car reach?
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1answer
47 views

Angle of repose for cylinders and spheres

Is angle of repose of a cylinder or a sphere same as angle of repose of a block on an rough incline? How to calculate it for spheres and cylinders?
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0answers
42 views

Problem in constraint equations

In this, if I want the acceleration constraint between $M$ and $2M$, I write $AM+2AB$=LENGTH OF STRING, which on differentiating twice gives $a_{m}=2a_{2m}$(which turns out to be correct). However, ...
2
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2answers
68 views

How is direction of static friction not opposite in direction but perpendicular when dealing with centripetal forces?

I was trying to wrap my head around this solution, and the whole idea of a car moving around a level curve, how the friction supplies the centripetal force. But I still can't wrap my head around the ...
1
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3answers
91 views

Acceleration - Constant force vs force for an instant

I am reading about Newton's second law, and I am slightly confused. So I think I get that $F=ma$ can be used to find acceleration. I am struggling between two scenarios: constant force acting over a ...
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1answer
27 views

Is it possible to determine the depth according to waves at the surface of a fluid?

Is it possible to determine the depth of a lake (for example) according to the waves of a stone thrown in this lake ?
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1answer
63 views

How do I properly apply the parallel axis theorem to a rod-sphere system rotating about its center of mass?

In the image below you see a rod with a sphere attached to its right side. The rod-sphere system is rotating around the entire system's center of mass. How do I apply parallel axis theorem to find the ...
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1answer
35 views

Calculating position of a particle at time $t$ in a gravitational field

I'm working on a piece of code that is supposed to visualize a particle bouncing up and down from the ground (somehow magically we can give it velocity upwards when it is on the ground). I figured ...
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0answers
19 views

Gyroscopic precession force translated 90 degrees? [duplicate]

I was watching a video on propeller gyroscopic effect, please take a look at this 1 minute segment (up to 6:06): https://youtu.be/QGWbjGqmoWo?t=307 Alternatively, here is a summarizing image from ...
1
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2answers
48 views

Two blocks accelerating at different rates in an accelerating pulley [closed]

Two masses are connected by a string which passes over a pulley accelerating upward at a rate as shown. If $a_1$ and $a_2$ are the accelerations of bodies 1 and 2 respectively, find the value of $A$ ...
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2answers
57 views

Does a conservation of momentum problem need to specify velocity, not just speed?

Problem: A $100$ g bullet is fired from a $10$ kg gun with a speed of $1000$ m/s. What is the speed of the recoil of the gun? This problem can be solved, if it can, using the law of conservation of ...
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0answers
43 views

Finding position with respect to time along a trajectory across a sphere (orbital mechanics)

When trying to find an object's position with respect to time on a ballistic trajectory along a curved surface, what equation should I use? I know that when adding force to an object to achieve ...