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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Atwood machine problem [closed]

Sorry for the bad drawing, but I hope that this will help you get a hold of the problem. Consider an Atwood Machine with a total of two blocks, a mass less pulley, ideal string. One block rests on ...
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1answer
905 views

How Can force exist without acceleration?

From what I understand acceleration does not cause a force, but rather forces cause acceleration, so if I have a ball moving with CONSTANT velocity, that hits a wall, then the wall must apply a force ...
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4answers
181 views

Why force $F$ is $ma$ but not $md$ or $mv$? How can I observe and understand “force” in real life?

As a layman, i can calculate approx "displacement" just by observing the moving object. And accurately by using a simple "scale". Similarly, again, I can calculate angle from origin by using ...
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1answer
104 views

Confusing Classical Mechanics Question

I don't want this to be a "do my home work question" so please tell me how I can make this question helpful for other people. In my physics assignment I found the question below. I'd think that both ...
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2answers
197 views

How is it possible to move something without completely lifting it?

For example, let's assume a chair here: It can be "slid" across the force if we use minimal upwards force, but not enough to actually "lift" the chair. Why should it move? Here's a better example: I ...
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154 views

Maxwell's demon - scaling down from something that seems to work

[I have updated the below description to clarify that the mechanism does not depend on a truly frictionless implementation. Also, since 2 commenters apparently assumed that I was proposing a ...
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5answers
763 views

Person Pushing a Block vs. People Pushing off Each Other - Newton's Third Law

I have read so many forums on this and I still do not understand and it's affecting my ability to move forward with learning physics right now. Imagine the following scenario: a person on a ...
2
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1answer
204 views

Is there a better, faster way to do this projectile motion question? [closed]

The question is In a combat exercise, a mortar at M is required to hit a target at O, which is taking cover 25 m behind a structure of negligible width 10 m tall. This mortar can only fire at an ...
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1answer
128 views

Confused about elasticity and collisions

I was solving the following problem and the explanation to it confused me. There are two objects with mass $m$ and $M$, respectively. The object with mass $m$ has a velocity of $\sqrt{2gl}$ and ...
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1answer
208 views

In a game of tug of war, what concepts are involved in determining where the rope breaks?

Assume that in a game of tug-of-war the rope ends up breaking. What concepts/factors would contribute to the position of where the rope breaks?
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2answers
4k views

Constant Velocity 'Force'?

According to Newtons second law: F = ma, if acceleration is zero then the force must be zero, but assuming you have an object moving with a constant velocity of say 2 m/s, and that object strikes you, ...
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0answers
88 views

Do vortex tubes work with a reversed end plug?

Would a vortex tube still work if instead of a cone plugged into the 'hot' end you had a smaller hole on the 'cold' end? As I understand it, the point of the cone on the hot end is to only allow the ...
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2answers
144 views

Work done on stationary rocket

Suppose I have a rocket thats exerts a force (with negligible loses in mass), which cancels out the downward force of gravity. Clearly my rocket could be moving at a constant velocity (ignore air ...
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1answer
910 views

Proving Kepler's 1st Law without differential equations

Is there a way to show that motion of Earth around the Sun is elliptical (Kepler's 1st law) from Newton's laws without resorting to the use of differential equations of motion?
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1answer
223 views

How did Newton find the relationship between force, mass and acceleration? [duplicate]

I have been told always that $F$ is directly proportional to acceleration. My question is that for finding such a relationship there should be source that produces desired force and in which the ...
2
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0answers
122 views

Conservation of Mechanical Energy [closed]

I am currently trying to tackle the problem: A 2.0 kg bundle starts up a 30° incline with 125 J of kinetic energy. How far will it slide up the plane if the coefficient of friction is 0.30? ...
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1answer
505 views

Distance formula in kinematics?

I've always seen it $d = v_i t + \frac{1}{2} at^2$ However, I also saw it as $d= d_i + v_i t + \frac{1}{2} at^2$ where $d_i$ = initial position. This was applied to 2D kinematics. Can anyone explain ...
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2answers
492 views

Intuitive understanding of centripetal vs. centrifugal force

I am having trouble understanding how centripetal force works intuitively. This is my claim. When I have a mass strapped on a string and spin it around, I feel the mass pulling my hand. So, I want ...
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2answers
158 views

Is mass proportional to the displacement from equilibrium in Hooke's law?

If I look at Hooke's law as it's defined in my textbook, it looks like: $F = -k\Delta s$ Therefore, the restoring force of an ideal spring will be proportional to the displacement from equilibrium, ...
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1answer
45 views

Acceleration on an inclined rail [closed]

I have to use $\vec{P}+\vec{R_N}+\vec{F_f}=m\vec{a}$ with $\|\vec{F_f}\|=\mu\|\vec{R_N}\|$ to express the acceleration as $$a_{x'}=g\sin\alpha(1-\frac{\mu}{\tan\alpha})$$ The configuration is (sorry ...
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2answers
175 views

Scaling: Gravity and Friction

I understand how doubling the length of a shape quadrupes it's area and the analog in 3 dimensions. My question however relates to other physical quantities, for example gravitational field strength. ...
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3answers
279 views

Newton's 3rd law [closed]

So i read this in some article on the net Consider a boy is standing at distance of 10 metres from the wall. Boy holds a rubber ball and cloth ball in his hands. Firstly, the boy throws rubber ...
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2answers
271 views

Moment of inertia around two axes

In the this chapter of an online pdf we are given an equation for the deflection of a beam: $$\frac{d^2y}{dx^2}=\frac{\overline{M}}{E I}$$ where $E$ is the modulus of elasticity, $\overline{M}$ is the ...
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0answers
56 views

What is the work done by friction on an arbitrary curve? [closed]

Here is the question, I have a particle with mass of $m$ moving on an arbitrary curve $y=y(x)$ with friction coefficient $\mu$. Force $F$ is applied to the particle with the equation, $\vec{F}= ...
2
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1answer
333 views

How do we know the Earth orbits around the Sun and not the other way around? [duplicate]

I know that describing the trajectory of all planets in the solar system around the Earth is much more complicated than if we take the Sun as the reference point. But besides this, what is the ...
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1answer
244 views

Period of small oscillations [duplicate]

A light elastic string is stretched between two points, one lying vertically below the other. A particle is attached to the mid-point of the string, causing it to sink a distance h. Assuming that ...
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2answers
290 views

Does anti-lock braking system (ABS) perform reverse rotation sometimes?

In cartoons we can see, how vehicles brake by rotating wheels reverse. Will this be helpful sometimes in real situations? I know that the main tactics of ABS is to maintain tractive contact. But may ...
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5answers
491 views

Motivation for form of Lagrangian

This question (in lagrangian mechanics) might be silly, but why is the Lagrangian L defined as: $L = T - V$? I understand that the total mechanical energy of an isolated system is conserved, and that ...
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0answers
142 views

How forces are in this shape? [closed]

I consider friction at zero. No gravity here. It's a theoretical problem. I placed some compressible balls in a volume like this: The volume is fixed. Balls can't escape. Balls are considered like ...
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4answers
351 views

When is “Inertia” Negligible?

I have started to read Strogatz's Nonlinear Dynamics and Chaos and I have come across an interesting bit. He states certain damped oscillators may be modeled as having no inertia term, I.E. $$m ...
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2answers
197 views

Under what conditions, will a projectile motion follow a half circle?

What came to my mind is to throw an object far from the earth with a particular speed equal to $$V_{sat}=\sqrt{\frac{G\times M_{central}}{R}}$$like satellites. However, it would follow a full circle.
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1answer
230 views

Change in weight by the change in mass of Earth and its radius [closed]

If the mass of Earth is four-times bigger, and the radius of Earth is two-times smaller, what would be my new weight compared to my current weight?
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0answers
467 views

Work, Energy, Power, Force question [closed]

Question: 3 boys push a small car 25 m up a hill inclined at 19° to the horizontal. The car has a weight of 860 N and they push it at a steady speed of 0.5 m s-1 against an opposing force of friction ...
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2answers
779 views

Mass-spring system on an incline

I am reviewing for an exam next week, and this is one of the questions I am stuck on. I have the mass-spring system above with spring constant $k$ on a frictionless incline. I would like to find the ...
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1answer
222 views

Artificial Gravity [closed]

Consider a structure that is in the shape as shown below rotating about an axis through its middle perpendicular to the long axis in order to provide artificial gravity. What would an ...
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3answers
235 views

Does unitarity imply conservation of energy?

Not too long ago, someone began to discuss the thinking and motivation behind the Lagrangian and its formalism for the Newtonian framework and an intuitive understanding of such formalism. Somehow, it ...
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0answers
81 views

Planatary motion of newtonian force [closed]

According to the Newtons gravity we can write, $$\vec F = \frac{\hat r_{12} G m_1 m_2 }{r_{12}^2}$$ and we are well known that this law satisfies the planetary motions. What changes will we see if we ...
0
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1answer
71 views

Evaluating $v$ for orbiting a golfball [closed]

The curvature of Mars is such that its surface drops a vertical distance of 2.0 meters for every 3600 meters tangent to the surface. In addition, the gravitational acceleration near its surface ...
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1answer
58 views

Calculating back-reaction forces for an ensemble of slowly moving, classical charges

Suppose you have a set of charges that are Newtonian (not quantum and not fast-moving) point particles. They are subject to known (but not necessarily constant) external forces ($F_{ext}$), as well as ...
0
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1answer
6k views

Rope tension between two objects [closed]

Let me explain the picture just to make sure. Object with mass 2 kg is being pulled with a force of F = 14.4 N. The whole system has an acceleration of a = 2.8 m/s^2. The friction coefficient ...
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0answers
517 views

elastic potential energy of a spring when compressed [closed]

A small ball with a mass of 1 kg rolls down a long frictionless inclined ramp, which is at an angle 30 degrees above the horizon. A linear spring, whose length is not negligible, is attached to the ...
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1answer
180 views

Determine if an object is in orbit

I am planning on doing a space simulation program with full physics and as part of a hack to avoid too many issues with number precision I was going to switch orbiting objects to a calculated orbit ...
3
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1answer
1k views

Can the velocity of the center of mass of two spheres change after a collision?

I'm curious as to whether or not the velocity of the center of mass of a system comprised of two spheres can change after the two spheres collide. Looking at the equation for the velocity of the ...
5
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2answers
288 views

Normal force of ball sliding on concave surface

Imagine a ball is sliding along a surface shaped like $y=x^2$. Like , but please ignore the fact that the center of the ball is on the surface instead of the edge. When the ball is stationary, I can ...
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3answers
246 views

Does Newton's first law state something substantive, or is it merely describing a convention?

Newton's first law is often said to define what an inertial frame is - namely, a reference frame in which a body not acted on by a force will move with constant velocity. In other words, a frame where ...
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1answer
164 views

Forces on a helical screw?

The common screws which we use, are right handed helices, the simplest parametric equations of which are:- $$x(s)=\cos(s),y(s)=\sin(s),z(s)=s$$, with $z$-axis as the axis of the helix. My question ...
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3answers
623 views

Explanation of homogeneity of space and time by giving examples?

while reading landau lifshitz i came across these three terms:- homogeneity of space. homogeneity of time. isotropy of time. it will be a great help for me if someone can explain it to me by ...
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1answer
6k views

String tension in vertical circular motion

Suppose that I have a point mass attached to a massless string and I am rotating it vertically. That means The mass is in uniform circular motion and the path of its motion is vertical circle. How ...
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1answer
82 views

Impulse Response and Linearity

Lately in my physics class (2nd-year undergraduate) we've been learning about the impulse response of systems and using Green's Functions to model the response of a system to more complicated input ...
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1answer
144 views

Does angular momentum conservation imply that angular momentum $J$ is parallel to angular velocity $\omega$?

In other words, does $\frac{dJ}{dt} =0$ imply $J \times \omega =0$? Counterexamples or proofs would be helpful! EDIT: This question originally asked if $\frac{dJ}{dt} =0 \Leftrightarrow J \times ...