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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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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3answers
141 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
81 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 ...
3
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3answers
133 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
63 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
340 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
39 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
82 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
139 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 ...
2
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1answer
137 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,...
2
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2answers
113 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 ...
0
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2answers
66 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
98 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 ...
0
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1answer
44 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
20 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?
0
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1answer
94 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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1answer
79 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, if ...
2
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2answers
131 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 ...
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3answers
134 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
28 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
181 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 ...
0
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1answer
40 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 ...
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2answers
110 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
81 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
51 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 the ...
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2answers
801 views

Why does a ruler continue to slide after toppling?

I was playing with a small ruler by repeatedly toppling it, see diagram below: The ruler, standing $h$ tall and approximately a regular bar, is prevented from free-rotating by a fixed ridge (a book,...
-1
votes
3answers
158 views

What does Newton's first law of motion want to say? [closed]

Newton's first law of motion says "A body will remain in a state of rest or in uniform motion in straight line, unless acted by an external force." So if a body is accelerated or moved ...
2
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1answer
45 views

If the friction coefficients depend on the object's property, why do they change in sliding & rolling, despite the object being same? [duplicate]

I know that when you roll an object instead of sliding it reduces the friction you can easily move an object. Consider the object to have a weight $W$ on a horizontal surface and the two objects have ...
1
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2answers
226 views

Terminal Velocity of 100lb Hail [closed]

In the Apocalypse there is meant to be hail weighing 100 pounds or 45 kg. What would the terminal velocity be, assuming the hailstones are perfect spheres of solid ice? Also, is there a way to guess ...
1
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1answer
86 views

Question about solving a problem using Newton's Laws and work and energy [closed]

The question is this: Darla pushes a $5.0kg$ crate up a $2.0m$ high $20^o$ frictionless slope by pushing it with a constant horizontal force of $25N$. What is the speed of the crate as it reaches ...
0
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5answers
81 views

Static model of the Earth motion

Believe it or not, an old man I know in 2015 still negates the Earth orbital motion around the Sun. He believes the earth is rotating on itself and acknowledges this gives day and night on every ...
2
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2answers
67 views

Physical interpretation of Fourier $[x(t)]$ where $x(t)$ is the position of mass $m$ as a function of time?

If a macroscopic body of mass $m$ moves according to a certain law of motion like, for example, $$x(t)=A\cos(2\pi ft)$$ then what physical interpretation can be attributed to the Fourier transform of $...
4
votes
1answer
140 views

The Lagrangian of a Rocket

I am trying to understand how to write the Lagrangian of a system which consists of a rocket losing gas mass in a rate of $\frac{dm}{dt}$, the gas moving in a velocity of $u_0$ in the rocket's view? ...
2
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1answer
63 views

Universe Expansion - Could galaxies be moving away from each other due to photon bombardment?

We know galaxies are moving apart from each other due to the ability to look at the color shift of those galaxies. The fact that galaxies are moving apart seems to be most-widely attributed to the ...
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2answers
70 views

How do gravity anomalies on Earth comply with conservation of energy?

Gravitational acceleration varies from place to place on Earth in a range of about 0.02 percent and is caused by density distributions within the Earth. Imagine an experiment where you move around the ...
2
votes
1answer
76 views

Does third law of motion apply to light or EM waves? [duplicate]

Third law of motion - "For every action there is an equal and opposite reaction" I was considering the situation, where I may be motionless in space with only a flashlight and no forces acting on me. ...
2
votes
1answer
103 views

Perturbation Method in Mechanics: Average velocity of a small mass on a vibrating inclined plane [closed]

I've stumbled across this delightful and difficult collection of problems, by Jaan Kalda. The following problem has stumped me. (It's probem 16 on the sheet, which I have provided as a link) http://...
0
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3answers
152 views

Does the work done by a person equal the work done on the object in this situation?

If you applied a constant force over a floor that has friction on an object, would the work done by the person equal to the work done on the object? Assume that the floor is flat and that the object ...
23
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4answers
5k views

Why doesn't a spinning object in the air fall?

Let's say I have a ball attached to a string and I'm spinning it above my head. If it's going fast enough, it doesn't fall. I know there's centripetal acceleration that's causing the ball to stay in a ...
1
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0answers
43 views

What does the Scattering Amplitudes tell us about the interactions of matter

I am confused as to the role of the wave function in quantum mechanics. My understanding is that the wave function/state vector is purely a algorithm or mathematical means to compute the results of ...
1
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2answers
49 views

Does air resistance give a falling skydiver weight?

An observer in free fall is weightless as he is accelerating at 9.8 m/s^2. However, when a skydiver jumps from a high plane, his acceleration gradually slows until becoming 0 m/s^2 at terminal ...
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2answers
33 views

Kinetic Energy and a force [closed]

An object is moving at a constant velocity mass $m = 5 kg$ velocity $v = 20m/s$ Kinetic energy $K = 1000 joules$ If I divide $K$ by the distance traveled in 1sec I get a force $f=50N$ What is ...
0
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1answer
71 views

Properly deriving the formula for the kinetic energy

I am a physics student and recently attended my first lectures. One thing that strikes me even now was the way the professor derived the formula for the kinetic energy. He started with the (already ...
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votes
1answer
65 views

Zero Energy State of a Mechanical System? [closed]

Would a mechanical system in a particular frame (when I say mechanical I mean pulleys, elastic strings, etc.) that has no potential energy (loaded springs, pulled back elastic, hanging weights, etc.) ...
0
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3answers
101 views

What's the work done by a spring on a block when it moves from extreme to mean position?

I really don't know where am I doing it wrong, but block when it moves towards mean position displacement will be along the force right, so the force acting on block will be $+fxdx$ Integrating we ...
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2answers
43 views

Phsyics Energy Problem + Concept

A simple problem really. Part 1 Suppose a ball ($20. ~kg$) was shot straight up with an initial velocity of $+50~m/s$. a. Assuming that all of the ball's initial $E_k$ was transformed into $...
0
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1answer
321 views

When dealing with pulleys and hanging masses, does one add or subtract tensions to find torque?

I'm very confused on this problem. A pulley has two hanging blocks on either side with one having a greater mass. To find the torque, do I have to add the tensions of both the blocks or subtract the ...
0
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3answers
49 views

Do I need to have a force acting in an opposite direction to feel the force of acceleration?

Suppose I'm in a rocket, accelerating away from the Earth. While I'm accelerating away from the Earth in the rocket, I can feel the force of acceleration. Now, let's suppose we take away the Earth, ...
2
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0answers
73 views

Precession of angular momentum vector

I'm studying Classical Mechanics on Goldstein's book, so I'm using his terminology and notation. First I'll explain where the question comes from: consider a heavy symmetrical top and consider the ...