All Questions
Tagged with kinematics classical-mechanics
255 questions
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3
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505
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Relative Velocity of two particles [closed]
If two particle are neither approaching towards nor receding away from other then their relative velocity is non zero.
How is this possible??
5
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4
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229
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Is this a kinematics paradox?
You consider a shaft which can rotate freely (there will be of course a frame with ball bearing to hold the shaft firm and to allow it to rotate with low friction); fixed on this shaft there are two ...
2
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1
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362
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What is the reactionary force exerted on a swing?
On a playground swing, children quickly learn how to swing higher and higher by timing their body motions with the resonant frequency of the swingset. But it occurs to me that it seems you're making ...
3
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3
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893
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Newton's Second Law in vertical launch of a rocket
Consider a rocket being launched vertically.
Let $T(t)$ denote the thrust from the engine and $M(t)$ be the total mass of the rocket at time $t$.
At $t=0$, $T(0)=M(0)g$ (so that the normal force due ...
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2
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466
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Why distance between 2 particles is independent of frame?
I was solving question in kinematics related to minimum distance between particles there they said that distance between two particles is independent of frame the distance they both measure between ...
4
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1
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780
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Is Centripetal Velocity a Thing?
I'm quite new to physics so this question may sound dumb for many of you. But when I was learning about uniform circular motion, all sources I can find talks about centripetal acceleration, and, when ...
3
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1
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137
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Average Velocity ($\vec{\bar{v}}$) Intuition and Analogy for Non-Uniform Acceleration
Background
So I was trying to make as much sense out of kinematics through intuition after having taken my first semester of university physics, and I've stumbled onto a dillema that I can't seem to ...
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1
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83
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why the velocity in some constrained motion is greater than the provided velocities? [closed]
Suppose the string provided is inextensible and massless.
The velocity of $C$ is $2$ m/s and the angle theta is $37^\circ$ then we get the velocity of ring $A$ to be $v = 2/ \cos37^\circ$ i.e. $10/4$.
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1
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153
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Finding The Trajectory of particle Kept on a rotating surface
Suppose we "Keep" a particle on a circular, rotating turn-table, rotating with constant angular velocity $\dot{\theta}$, (i.e, the at $t=0$,when the particle makes contact with the table, the ...
2
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1
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128
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Does mass matter at all for kinematics vertical questions w/o friction?
This is the specific question w/o information on mass given, I think here is not enough info.
A block and a sphere are each released from rest at the top of an incline from the same height. The ...
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3
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246
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Why does this example seem to contradict conservation of energy?
Consider a 10 kg box on the bed of a truck accelerating at 1 m/s^2. Consider a reference frame where it starts at 0 m/s and ends at 10 m/s and then consider a reference frame where it starts at -5 m/s ...
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1
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Vertical motion [closed]
Ball $A$ is thrown vertically upward from the top of a $30$ m high building with an initial velocity of $5$ m/s. At the same instant, another ball $B$ is thrown upward from the ground with an initial ...
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3
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Considering body as a paricles, how the force is applied?
Lets consider a 2d box with nothing inside of it - just 4 walls, which consist of balls, connected by the force very similar to spring force. Look at the picture I draw.
When the force applied to ...
2
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1
answer
114
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Calculate local linear accelerations from trajectory
I'm trying to simulate linear accelerations and angular velocity of a vehicle which drives on a flat surface. For this, I want to use a trajectory consisting of position ($x_i, y_i$) and orientation $\...
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1
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319
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Path of an object in gravitational field [duplicate]
How do you prove that path of a satellite or a planet is a second degree curve? In other words, how do you prove Kepler's law which states that planets move in elliptical paths?
3
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3
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444
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Velocity after applying a force in the vacuum
I’m sorry for so simple question, but I just need to be sure.
I understand, that the changing of the speed occurs only when the force is applied, I understand that if one punch a ball in the free ...
1
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1
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76
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Determining acceleration in order to meet a space-time-velocity reservation
An Example
A train on a single line track is told to be at position $x_{res}$, at time $t_{res}$, and to be moving at exactly $v_{res}$ when it hits that point. Where $_{res}$ denotes the reservation....
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1
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148
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Rigid bodies: angular velocities, momentum, Inertia Tensor, rotational kinetic energy. Books suggestions? [duplicate]
I'm having a hard time with understanding how to model the rotational kinetic energy of rigid bodies. I will appreciate any good suggestion about resources such as books or videos regarding topics ...
0
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3
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678
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Kinetic Energy and Braking Distance [duplicate]
A car traveling at 50km/h will move 44 extra meters from the moment its brakes are applied fully. If the same car travels 100 km/h on the same road, how far will it move from the instant its brakes ...
0
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0
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91
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How can I isolate the drag constant (C) for vertical motion with quadratic drag from the equation for peak height?
Some background on my problem: I have calculated the peak height of a rocket (with quadratic drag). As this will be used for a PID software application, I need to have the equation be expressing peak ...
1
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1
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58
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Does super position precede physical phenomena?
If a traveling wave has amplitude of d, it feels certain amount of force at that moment in time when it is displaced for equilibrium. Thus there is also strain on the string corresponding to that ...
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3
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3k
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How to prove the relativistic momentum? [duplicate]
As far as I know, the relativistic momentum of a particle is given by the equation: $$p=\frac{m_0v}{\sqrt{1-\frac{v^2}{c^2}}}$$
where $m_0$ is the mass of the particle and $v$ is the velocity of the ...
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1
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91
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The velocity of an object leaving the inclined plane
I saw the question below in our physics textbook. It asks
A block of mass m is released and slides down on the frictionless inclined surface ( the inclined plane is of concrete and doesn't ...
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1
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51
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Rotation of top of symmetries
while learning about rotation, I started to wonder what forces will come into play. Lets picture a top with two masses centered at (-1,0,-1) and (1,0,1) with rods connecting the masses directly to the ...
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2
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112
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How is energy conserved in terms of "Work"
Basic equation of work is given by $F\cdot s$. When work is done, the energy is stored either in form of potential or kinetic. My question arises when we look at a case of applying $m g$ of force ...
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2
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76
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When we can consider a body to be point sized?
In motion we idealize big object to be point sized. But we don't do it all the times. I am having some confusion on it. Please tell when we consider objects to be point sized?
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2
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1k
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Relative velocities in Circular Motion
Recently I saw the following interesting problem
Ann is sitting on the edge of a carousel that has a radius of 6 m and is rotating steadily. Bob is standing still on the ground at a point that is ...
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0
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Quick question: can you describe the direction of motion relative to a particle?
In Gregory R.D.'s Classical Mechanics, he has written "Relative to a single particle, the only thing that can be specified is distance from that particle".
My question is, isn't it possible to ...
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1
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771
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Distance from ground to start suicide burn with initial height [closed]
In the figure below, the rocket is dropped with no initial velocity at a height of $h$. $d_f$ (free fall distance) is the distance in which the rocket is in free fall. $v_b$ is the velocity due to ...
0
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1
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114
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Velocity of an object orbiting on a string
First, I'm sorry if this question is dumb, incoherent or vague - I never really studied any physics and this might be out of my grasp, but I tried to apply some of the math I know and figure these ...
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2
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What is the direction of linear motion after this impact?
I've been thinking about a situation where I am not sure what the resulting motion would be.
This is what I am thinking,
1) P is the point of application of force. If there are two force components ...
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1
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Finding tangential and normal velocity from a curve [closed]
How do you find tangential and normal velocity from a curve?
I know how to find dy/dx, but I have no idea how to obtain ut and un and dv/dt.
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3
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2k
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How is final velocity negative when acceleration is in positive direction?
When a body starts from rest and starts accelerating in positive direction and moves certain positive distance, its final velocity is given by :
$$v^2 = u^2 + 2as$$
Solving it gives two values of $v$, ...
4
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1
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186
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Why is the kinetic energy a fixpoint of the Legendre transformation?
Question: Why is (from an intuitive standpoint) the kinetic energy $T$ a fixpoint of the Legendre transformation, i.e. $\frac{\partial T}{\partial \dot q}\dot q-T = T$ for any general coordinate $q$? ...
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1
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78
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circular(ish) motion?
how would one describe as a function of time the position vector of an object with initial position $\vec{x_0}$ and velocity $\vec{ v_0}$ experiencing a central force of constant magnitude around the ...
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1
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57
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Change of variable in function
Suppose I have a function $h(\theta)$ measuring the height of a piston, with $\theta = \omega t$. I would like to know the vertical acceleration of this piston as $\omega$ changes at the point $\theta ...
3
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2
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127
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How to decelerate from velocity $v$ to stop time $t$ over distance $d$? [closed]
I'd be grateful for some help with this problem I am trying to solve.
Let's say that I have an object travelling at a velocity $v$. I want that object to come to a halt in time $t$ AND travel exactly ...
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2
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232
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Kinematics of particles
Do particles have to move in a straight line to apply Suvat equations?
I always perceived that they do because acceleration can mean a change in the magnitude of velocity, a change in direction or a ...
1
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2
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224
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Why does wave keep on travelling despite destructive interference?
I've problem here. Imagine you've a line of spheres that are attached to each other with springs. You push one sphere down hard. it drags its neighbors down and which in turn pull their neighbors and ...
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1
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69
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Confusion about valid set of virtual displacement
The answer of the problem below makes me confused about my thinking about virtual displacement...
Consider the system in the figure below, similar to mechanisms used for aerial filming of sporting ...
2
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1
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582
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Motion equations for Woodpecker toy (multibody system)
I am trying to understand a rigid multibody model of a Woodpecker toy (see figure below). Now I am not going to go into details about the model or justify this approach, I am just trying to understand ...
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1
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Why is the direction of net force on an object and the direction of acceleration of that object is different in this situation? [duplicate]
A $ 2.0 kg $ block is being pulled across a frictionless table by a rope with negligible mass at an angle $ \theta=60° $ (from positive direction of $ x $ axis, we have taken horizontal surface of ...
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2
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244
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Why is the direction of net force on an object and the direction of acceleration of that object different in this problem?
A $ 2.0 kg $ box of cucumber extract is being pulled across a frictionless table by a rope at an angle $ \theta=60° $ (from positive direction of $ x $ axis, we have taken horizontal surface of table ...
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2
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15k
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The human body can survive an acceleration trauma incident (sudden stop) if the magnitude of the acceleration is less than [closed]
The human body can survive an acceleration trauma incident (sudden stop) if the magnitude of the acceleration is less than 250 m/s². If you are in an auto- mobile accident with an initial speed of 105 ...
1
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2
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414
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Inconsistent Results with Momentum and Kinetic Energy
A speed skater with a mass of $m_1$ kg is moving at $v_{1i}$ m/s. He prepares to push the next speed skater of mass $m_2$ kg moving at $v_{2i}$ m/s. After the push, the velocity of the first skater ...
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3
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1k
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If mass is doubled, how much more power is needed to sustain the same speed?
My problem involves an object completely immersed in a fluid, moving at some speed, using a certain amount of power to sustain that speed. It could be an airplane or a torpedo, among other things.
(...
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1
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25
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Kinematic Modelling with clockwise angles defined as positive
It seems when modeling a system for which an clockwise angles is defined as positive, the resulting equations become wrong.
For example :
In the picture below $\theta_x$, the orientation of the ball,...
1
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0
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54
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How to accurate scale start velocity in projectile motions? [closed]
I have projectile motion where the angle $\alpha$ is $45^\circ$, and the start velocity is $45\ \rm{m/s}$. We can then expect it to land about $206.422\ \rm m$ away; however, if I were to change/...
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1
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151
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Angular velocity by velocities of 3 particles of the solid
Velocities of 3 particles of the solid, which don't lie on a single straight line, $V_1, V_2, V_3$ are given (as vector-functions). Radius-vectors $r_1, r_2$ from third particle to first and second ...
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1
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343
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Smoluchowski theory of Brownian Motion
I am studing Brownian motion, in particular I am reading the book "Brownian Motion, Fluctuation, Dynamics and Application" by Mazo. Now I am dealing with Smoluchowski theory, but I am having some ...