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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What does it mean 'the observer' in Quantum Physics? [duplicate]

Is it only necessary a human consciousness? A measurement device? Can it be said that any of them cause the wave function collapse?
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687 views

How do traveling waves pass through a standing wave node, if the node doesn't move?

I'm having trouble with the explanation that a standing wave in a string is the superposition of traveling waves. The nodes in the diagram above are points where the particles of the string's ...
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1answer
203 views

Bullet hits block. Show that linear momentum is not conserved [closed]

"..." First, we will familiarize us with a collision between a homogeneous beam of length, $L$, mass $M$ attached with a frictionless hinge in point $O$ at one of the endpoints of the beam. The ...
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1answer
225 views

Tangential and radial acceleration in projectile motion

I'm currently learing kinematics, specifically projectile motion and as an example in my textbook is a bullet fired at some angle. I understand the derivation of formulas to describe that motion and ...
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2answers
187 views

Magdeburg Hemispheres

The Magdeburg Hemisphere experiment was the experiment that showed the effect of pressure differences on a vacuumed sphere. We know that the Force caused by pressure is $\Delta p A$ and so you can ...
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3answers
200 views

How is angular momentum conserved if a bullet hits a wheel?

Suppose my system involves: 1) A mounted wheel with some outward flap 2) A bullet already in motion Initially the net angular momentum is 0 and the net kinetic energy is just that of the speeding ...
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1answer
199 views

Geometry in diagonal matrix and inertia tensor

For this problem, can anyone explain to me why when $x_1$ axis is aligned with the diagonal of the cube, the resulting inertia tensor will become diagonal? How to interpret this result geometrically? ...
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2answers
88 views

Do I need to take weight of the rocket into account when calculating escape velocity?

Here there is the old problem. I know from the old problem that the work $W_v$ that I need to make a rocket fast enough to reach the escape velocity is $$W_v= G \frac{mM}{r}$$ therefore because ...
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1answer
533 views

Truck moving uphill, object suspended from ceiling, determine acceleration [closed]

A truck is moving with constant acceleration $a$ up a hill that makes and angle $\phi$ with the horizontal. An object of mass $m$ is suspended from the ceiling of the truck by a light cord. If the ...
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1answer
303 views

Moment of Inertia of a sector of a circle [closed]

I am trying to find the moment of intia about its centre of a sector of a circle of radius $a$, mass $m$ and angle $\pi/3$. I have found the answer it is $\frac{1}{2}ma^2$ but originally tried a ...
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1answer
128 views

Escape velocity problem

I was given a problem at school: How much Energy do we need to make a rocket of mass $m$ faster than the escape velocity so that it can travel in outer space? Here's how I worked: I know that ...
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1answer
419 views

Mechanics question - ladder leaning against a wall

I am struggling with part a) of this question: Here is the solution: In part a) they prove that $F \leq \mu R$ is false for this system. So as $F$ is neither less than nor equal to $\mu R$ it ...
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1answer
117 views

Trajectory of falling object, with and without initial velocity

If an object is dropped from a roof with no initial velocity and wind is blowing along the side of the building exerting a constant force on the object, then its trajectory will be a straight line. ...
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1answer
96 views

Additive constants of motion

I've read in a book, that in general case energy $E$, momentum $\textbf{p}$ and angular momentum $\textbf{M}$ of a closed system are the only additive constants of motion, that is, if I have $N$ ...
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1answer
48 views

Doing a spring experiment, and need to find the stretch required

I'm doing an experiment where I have to calculate the stretch of a spring needed for it to launch itself into a trashcan located some distance away. The spring is located on the edge of a ramp that is ...
7
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2answers
296 views

How do we know if a formulation of classical mechanics is correct?

For example, the Lagrangian formulation. I may be missing something, i.e. not having done it in enough detail, but here is my issue: from the definition of the lagrangian ($\mathcal{L}$) and from ...
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1answer
66 views

Unknown Mass Spring Problem [closed]

A student conducts an experiment to measure the motion of two unknown masses (A and B) along a smooth table. A constant force of 1 N was applied by means of a string connected by a falling weight. A ...
2
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0answers
186 views

Can you give example of some problems with solutions in each of Newtonian, Lagrangian and Hamiltonian method? [closed]

I am a student from information system and just want to know about classical mechanics. I know Newtonian mechanics from high school and I have read about Lagrangian and Hamiltonian mechanics in ...
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0answers
49 views

Trouble understanding quantum mechanical picture of atom [closed]

This year in college we"ve had a lot of quantum stuff thrown at us, and we"ve only been doing classical mechanics till last year. We"ve been introduced to Schrodinger"s equation, electron waves, what ...
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1answer
86 views

Comparison: graph of radius vector and angular velocity

$$ r(t)=R \left(\begin{array}{c}\cos(\omega t)\\ \sin(\omega t)\end{array}\right) , $$ $$ v(t)=\omega R \left(\begin{array}{c}-\sin(\omega t)\\ \cos(\omega t)\end{array}\right) $$ where the symbols ...
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1answer
95 views

Balancing stick on hand - inverted pendulum motion

How do I calculate the velocity and acceleration of a stick that is vertically on my hand? How fast and far do I need to move my hand from side to side to keep balancing the stick? Assuming that we ...
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3answers
207 views

Why isn't angle of launch used in this kinetic energy equation?

Question: A stick is thrown from a cliff 27 m high with an initial velocity of 18 m/s at an angle of 37 degrees above the horizontal. a) use the law of conservation of energy to determine the speed ...
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2answers
254 views

An intuitive proof of Bertrand's theorem

Is there a way to see that Bertrand's theorem is true intuitively. I mean without getting into too much mathematics ?
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65 views

what forces are present when slicing an object.

I found here:What happens when we cut objects? that it is due to fracture wood splits open when using a wedge. Does it only apply when the wedge is already in the wood? How about the moment before a ...
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2answers
306 views

Consider a horizontal surface with or without friction. Ideally, will a wheel rolling without slipping roll forever in both cases?

Suppose a wheel is rolling smoothly on a horizontal plane i.e., it is rolling without slipping. Now let's take the two cases of the horizontal plane: It has friction It is frictionless In the ...
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3answers
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What happens in a car crash?

My mom and I were in a car accident. We are ok, but I want to know how fast the car that hit us was going. We were stopped at a light. The car that hit us from behind was a big GMC SUV. Our car was a ...
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2answers
58 views

Difference between two equations

So again I have two equations: $$K= \frac{1}{2} m v^2 + \frac{1}{2} I \omega^2$$ And $$K_w = \frac{1}{2} I \omega^2 $$ What's the difference between these two? Thanks.
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1answer
53 views

Two equations for $y$ in projectile motions

I have two equations on my equation sheet: $$y=v_o t \sin \theta - \frac{1}{2} g t^2.$$ And then another: $$y_{\max} = \frac{v_o^2 \sin 2 \theta }{2g}.$$ I understand that the first one is an ...
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1answer
123 views

Rotation and fictitious forces

A bug eats through an apple and forms a vertical, infinitesimally thin canal parallel to the vertical diameter at a distance $\frac{R}{2}$ from the center. The apple rotates at angular velocity around ...
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1answer
96 views

Reference frame and centrifugal force

Imagine you are on a theme park ride in which you sit in a car and are spun around in a circle, basically like a giant centrifuge. An observer from the outside would say that there is no centrifugal ...
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8answers
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Does centrifugal force exist?

Currently in my last year of high school, and I have always been told that centrifugal force does not exist by my physics teachers. Today my girlfriend in the year below asked me what centrifugal ...
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43 views

How would you explain the difference between these situations?

I have been thinking about this for quite a while, but I just can't seem to formulate a coherent answer. In problem which I will denote (a), we have a man sitting on some sort of chair and he is ...
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1answer
299 views

Small Animal Terminal Velocity

I recently saw a cat fall probably 100 feet like in this video Cat Falls. It seemed as if the cat reached terminal velocity by the time it hit. Does this mean that cats (and other small animals) could ...
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1answer
115 views

Question concerning the Feynman Lectures of Physics

I am reading the Feynman lectures and at this point http://www.feynmanlectures.caltech.edu/I_13.html#Ch13-S3 it says as follows: The time derivate of the potential energy is $\begin{equation} ...
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955 views

Visualizing Tension in FBD — Rope With Mass

Asked to find the tension of a point that is halfway up a rope (where the rope has mass), given the system: The solution of the problem (FBD included) is as follows. In this diagram (Tm = tension ...
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1answer
248 views

Physics behind a match performing a trick on center of mass

https://www.youtube.com/watch?v=Ucdw0DDI4n8 I've seen another variation where the whole match stick turned to ash. What's going on in this trick?
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1answer
61 views

Stern Gerlach Experiment

Since l=0 for a valence electron in 5s state of silver, L=0 and therefore magnetic dipole moment is also 0 which means that the beam should not have deflected at all. So, we introduced the property of ...
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199 views

Truss Analysis with multiple moments creates linear combinations

So in my engineering statics course we have been doing a great deal of work with trusses and machines, and a part of the physics behind it has really been confusing me. Just as a note, I also have ...
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2answers
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Is the moment of a force the same about any point?

I know that when a body is is equilibrium There is zero resultant force in any direction, i.e. the sum of all the components of all the forces in any direction is zero The sum of the moments about ...
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141 views

Force of gravity in the event horizon [closed]

I recently posted a question about black holes and gravity (this) and I discovered the Schwarzschild radius: $r_s=\frac{2GM}{c^2}$. I thought with a friend of mine about the actual force (in Newtons) ...
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2answers
214 views

Integrating the divergence of a velocity field (Fluid Mechanics)

I'm looking more for verification of my answer as I'm not 100% sure how valid my integration is here: If I have a 2-D incompressible fluid velocity field given by ...
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2answers
69 views

2D vector components

Can any equation with a vector e.g. velocity be used with just the horizontal or just the vertical components, I am thinking of equations like Newton's laws, conservation of linear momentum etc. So ...
3
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1answer
414 views

Angular momentum depends on origin?

The angular momentum of a particle rotating about a point is given by $\vec{L} = \vec{r} \times \vec{p}$. Imagine a particle tracing a circular path on a flat table. If I put the origin of my ...
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66 views

What determines the speed required to pull a table cloth?

I was watching this show "Street Genius" on National Geographic and the host Tim Shaw demonstrated an experiment about Inertia, What he did was, He tied one end of a table cloth to a car through a ...
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1answer
91 views

Kronecker delta in inertial tensor

I feel confused in (11.9) how does the book prove the following identity: $$\sum\limits_{i} w_{i}x_{\alpha,i} \sum\limits_{j} w_{j}x_{\alpha,j} = ...
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2answers
645 views

When pressure is exerted on parallel hydraulic pistons, do they start extending at the same time?

If there are two hydraulic cylinders connected in parallel, each with a different load (shown in the picture below), will they start extending at the same time? I'm having a disagreement with my ...
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1answer
69 views

Will it start rolling?

Suppose you have a wheel standing stationary on a rough horizontal surface. Now you apply a horizontal force at the top of the wheel. Now, will the wheel experience any force or will it just start ...
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107 views

Universal gravity at small distance

Could it be that there is simply a maximum gravitational force that two bodies of finite mass can exert on one another? This would occur at $r=0$, so maybe there is some really really really small $a$ ...
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1answer
94 views

Centrifugal force for non uniform circular motion [closed]

If a body is under non-uniform circular motion, will it experience or will there be any impact of centrifugal force on the body upon eliminating the centripetal force? update-sorry.the title of ...
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2answers
268 views

Relative motion. Setting course of closest approach

Let $r_{P/Q}$ be the position vector of $\overrightarrow P$ relative to vector $\overrightarrow Q$ and $v_{P/Q}$ the velocity vector of $\overrightarrow P$ relative to $\overrightarrow Q$. Suppose ...