All Questions
Tagged with kinematics classical-mechanics
255 questions
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Formula - Bounce height with respect to time
I'm trying to graph a bounce with respect to time. I have these formulas:
$\frac 12 mV_2^2 = mgH_2$
and
$H_2 = \frac{1}{2} \frac{V_2^2}{g}$
I will have a series of $H(t)$ formulas as I know how to ...
- 133
0
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0
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182
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Particle Disintegration Range of Angles (Landau& Lifshitz)
In the particle disintegration problem in the book by Landau and Lifshitz (pg 44 question 3), it is asked to find the range for $\theta=\theta_1+\theta_2$, where $\theta_1$ and $\theta_2$ are the ...
- 109
0
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1
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Deriving some uniform circular motion equations
My question basically boils down to this. How do we derive these relationships.
1.)What is the relationship between radius and centripetal force? (inverse, but why?)
2.)What is the relationship ...
2
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2
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8k
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Half-atwood machine with accelerating pulley
This is a follow-up to my previous question, in which I am now trying to calculate the acceleration of the cart (as before, the block surfaces are frictionless). The mass $m_2$ is attached to $M$ via ...
- 1,605
-3
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2
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864
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Why the bob leaves the circular path when tension in the string becomes zero [duplicate]
In vertical circular motion of a bob attached with a string, we say that the bob leaves the circular path when tension in the string becomes zero.
But even when tension becomes zero there's always a ...
- 295
2
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3
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528
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What was the motivation behind the work formula?
Surely there must be a reason we decided to use this as a metric for mechanical energy.How was it developed and what made it more acceptable than other work formula candidates (Like force over time, ...
- 566
3
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3
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881
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Is there an intuitive explanation of the work formula?
Upon learning calculus, I decided it was time to derive all of classical mechanics to give myself a good understanding of physics. What I found was that, while trying to do so, I would need some ...
- 566
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1
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126
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Why do systems with a fixed gear-ratio still use gears?
From my understanding, there are two uses of a gearing system: to change the speed of output rotation (trading it with torque), and to change the axis of rotation. Now, in a car, for example, it is ...
- 2,973
3
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4
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249
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Irreversibility Aristoteles law of motion
I am watching the second lecture from the theoretical minimum and do not understand the argumentation of Susskind.
For those who do not want to watch the video. It is about the law of motion from ...
- 573
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2
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6k
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Kinetic energy dissipation in braking a vehicle
Let's say a vehicle that weighs 20t is hauling along at 50m/s and we want to brake it down to a full stop.
The kinetic energy we need to dissipate into heating up the brakes is
...
0
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2
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67
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When considering the acceleration as constant? [closed]
I'm solving a simple dynamic exercise, exercise says:
"What is the absolute value of the force necessary to speed up a 500kg mass subject to 1600km/h in 1,8s, with the object from rest?"
Then I had ...
- 107
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1
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1k
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Minimum distance between two bodies attached by a spring
Take two bodies of masses m and M attached by a spring of constant K on a smooth horizontal surface. The system is at rest. A constant force F acts on body M, horizontally. To study the motion of the ...
- 162
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0
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47
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Optimal "Blow up" Configuration
Suppose you have three balls glued together. Two are red and one is blue. The system of balls is blown up by an explosion of pure energy (that conserves the center of mass frame) exactly at the center,...
- 5,421
7
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4
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Is there a formula that gives the position of an object depending on the time, but which doesn't allow the object to surpass the speed of light?
I have found these two formulas:
$v = at + v_0$
$x = \frac{1}{2}at^2 + v_0t + x_0$
a is the acceleration
v is the velocity
x is the position
t is the time
$v_0$ is the initial velocity
$x_0$ is the ...
- 1,643
1
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2
answers
2k
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Do rotation matrices rotate about inertial or body angles? [closed]
I have Yaw, pitch, and roll angles in that order (Euler 321) to apply to a body reference frame in cartesian coordinate system. I want to know what the body reference frame vector coordinates are ...
- 1,015
3
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2
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5k
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Hockey puck collision [closed]
I have a homework question in which a sticky hockey puck traveling at constant velocity parallel to the side of the rink strikes a stationary puck and sticks to it. The angels between centres at ...
- 316
2
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1
answer
206
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Shouldn't motion be represented as a Taylor series rather than a finite sum of functions or a polynomial? [closed]
Since the change in velocity of an object at rest prior to time $t_{0}$ implies a change in acceleration — that is, let's postulate, $ \mathbb{P} $, the object would have remained still, so there was ...
- 137
1
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1
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1k
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Work done: kinetic energy or area under F-ds curve?
Starting from $$F=ma = m \frac{dv}{dt} = m \frac{ds}{dt} \frac{dv}{ds} = m v \frac{dv}{ds}, $$ leads to work done = integral of F.ds = integral of mvdv = change in KE.
Suppose a variable force is ...
- 71
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1
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76
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Questions about basic jump physics
This is a problem a friend and I are working on for an undergrad reading course. Our goal at the end is to make an accurate two-dimensional model of the human jump using Processing by the end of next ...
0
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2
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1k
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A question regarding 3 bodies connected as a system
Let us consider three bodies of equal mass connected to each other with 2 ideal strings of length l. The three bodies are placed in a straight line
In this arrangement there is 1 body connected to 2 ...
- 162
0
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2
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895
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Finding the initial velocity of a vertical circular motion [closed]
A particle P is suspended from a fixed point O by a light inextensible string of length a. When hanging
at rest under gravity at A it is given a horizontal velocity u. The particle moves freely in a ...
- 135
5
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5
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How does an object's motion behave if dropped from an aeroplane travelling diagonally upwards?
Imagine an aeroplane travelling with velocity $v$ at some angle $\alpha$ from East to North.
A box is dropped from the aeroplane.
What would the projectile of the box be? Would it be a parabola with ...
- 4,637
2
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2
answers
954
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What is the percentage of energy recovery in Kinetic Energy Recovery Systems(KERS) in cars?
Kinetic Energy Recovery Systems (KERS) use flywheels to recover energy from the kinetic motion of cars. They use a rotating flywheel that generates energy as it rotates- this generates the electric ...
- 303
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1
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67
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Interaction of solid objects and change of trajectory
I have two solid objects. Each of them has an arbitary complex surface, which is discribed by set of vertices. The aim is to describe their interaction, result of which is the change in trajectory of ...
- 101
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1
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266
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A pearl that moves in a smooth vertical hoop
I wanted to ask about the situation of a pearl that moves in a smooth vertical hoop in circular motion as described in the following sketch.
According to a simulation found in the internet , a moment ...
- 407
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1
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87
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A pearl that moves in a smooth vertical hoop (Circular motion) [closed]
I couldn't understand something about the situation of a pearl that moves in a smooth vertical hoop in circular motion.
When the normal force equals 0 , the pearl didn't disconnect from the smooth ...
- 407
2
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4
answers
356
views
Acceleration and Circular Motion
Lets assume that there is a force that makes our body moves in circular motion.
We know that the acceleration of a body that moves in circular motion is Velocity ^ 2 / Radius .
How is it ...
- 407
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2
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212
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Query into the cumulative velocity of mounted platforms
Consider throwing a stone at an object from rest, it travels at Vms-1. Now throw that stone whilst running at Ums-1. It seems in the latter scenario the total speed of stone is V + U. Now imagine ...
- 227
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2
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3k
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Find the minimum value of velocity [closed]
Find the minimum value of the initial velocity $u$ of the particle such that the particle crosses the wheel of radius $R$.
Details and assumptions
$R=2m$
$g=9.8m/s^2$
Neglect air resistance.
All ...
- 265
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3
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1k
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A particle of mass $m$ moves with constant speed $v$ along the curve $y^{2}=4a(a-x)$ [closed]
I have complications to do the following problem:
A particle of mass $m$ moves with constant speed $v$ along the curve $y^{2}=4a(a-x)$. Find its velocity and acceleration vectors.
My first idea was ...
- 159
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1
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181
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Missing centrifugal acceleration
I am trying to get correct equations for acceleration of a point in reference frame A, given position, velocity and acceleration in rotating reference frame B.
Let $\mathbf{x}_A(t)$, $\mathbf{v}_A(t)$...
- 103
1
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1
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405
views
Objects falling on Slopes [closed]
An object falls on a slope and then rebounces....and it is known it hits the slope again...how do I calculate it's second point of contact with the slope....how can a projectory equation be used in ...
- 243
2
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1
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427
views
Problem Of Lazy Fish [closed]
Fish achieve neutral buoyancy (so they don't have to swim constantly to stay in place) via a swim bladder. A swim bladder is a little internal sack that they can inflate/deflate with air, which ...
-13
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3
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3k
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What would happen if an unstoppable force hits an immovable object? [closed]
I realize that the question a rather large paradox, but I do wonder if such a thing were true what would happen, assuming that neither of these "objects" can be destroyed by each other?
- 305
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1
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971
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Circular motion problem? [closed]
I am learning about circular motion and not quite sure how to approach this particular problem. Any help would be greatly appreciated!
A particle moves along a circular path over a horizontal $x$-$...
- 161
1
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2
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2k
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Conservation of linear momentum magnitude along a trajectory
I was once criticized for "taking angular momentum as momentum going
in a circle". I was loosely trying to state, in classical mechanics,
that in using conservation of momentum, one can switch between ...
- 3,808
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2
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2k
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6 Story Building Swaying, Normal? [closed]
Preface:
I'm currently sitting at my desk on a 5th floor in a South Florida office building, as I was earlier this morning when I felt the building sway slightly. It wasn't continuous and the ...
- 135
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2
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2k
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How to calculate pressure exerted on the wheels of a robotic car?
I need some help in designing my robotic car. So its going to have 4 wheels, each driven by a 12-volt motor. It occurs to me that the weight of the chassis itself will exert some pressure on the ...
- 219
5
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3
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3k
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Does more rain strike a vehicle while moving or while stopped (or neither)? [duplicate]
Assume there is a rainstorm, and the rain falling over the entire subject area is perfectly, uniformly distributed. Now assume there are two identical cars in this area. One is standing still, and ...
- 251
18
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5
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605
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Does the mass point move?
There is a question regarding basic physical understanding. Assume you have a mass point (or just a ball if you like) that is constrained on a line. You know that at $t=0$ its position is $0$, i.e., $...
- 181
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2
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Is a heavier skier faster? [duplicate]
Is it true that a heavier skier goes faster? If it is, why is that?
My intuition would be that the speed gained by a skier should be independent from its mass, since both its acceleration and the ...
1
vote
0
answers
59
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One dimensional motion with changing acceleration. Falling to a large body from a great distance [duplicate]
Possible Duplicate:
Radial fall in a Newtonian gravitational field
My math and physics are rusty. I am trying to calculate the time an object takes to fall to a large body. Before you answer $1/...
- 119
2
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2
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954
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Ideal 2D Unicycle Kinematics
A particle is connected to a massive wheel by a rigid rod. The wheel can roll without slipping on a horizontal surface. The particle is free to rotate around the centre of the wheel.
I believe the ...
- 23
4
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3
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Difference b/w Kinetics & Kinematics w/concrete example
(I know whether I understand this or not doesn't matter much to my work & study but am just curious.)
I still can't differentiate in my head kinetics and kinematics (similar thread is found but ...
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2
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5k
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Would this model of a boat move according to Newtons 3rd Law?
If i have a small toy boat with a sail, and i attach a fan onto it, FACING THE SAIL, which runs by solar. Once the fan turns on will the boat move or will it remain at rest. Apparently it wont because ...
- 15
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2k
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Can these figures demonstrating the safety of "Archery Tag" arrows be correct?
There is a new sport called "Archery Tag" that involves shooting opponents with foam-tipped arrows fired out of a real bow. The official Archery Tag web site presents data that claims to show the ...
- 209
1
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2
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153
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Acceleration: Value Disparity?
If we consider a ball moving at an acceleration of $5\ \mathrm{m\ s^{-2}}$, over a time of 4 seconds, the distance covered by the ball in the first second is $5\ \mathrm m$. In the 2nd second will $5\ ...
- 383
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1k
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The Double Integrator: Matching velocity and position as quickly as possible with only a limited amount of force available
If a body with mass $m$ begins at position $x_0$ with velocity $v_0$ and experiences a force that varies as a function of time $f(t)$ (and we ignore gravity, friction, and everything else that might ...
- 375
1
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2
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883
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Gears and efficiency/speed
For Christmas me and my brother got an AR Drone, the propellers are on a large gear, which is rotated by a small gear that is connected to the motor.
This means the small gear (and therefore the ...
- 6,987
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3
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415
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Do we know how matter moves matter? [closed]
I was surprised when reading an apologetics book recently that attempted a rebuttal of the claim that "An immaterial mind cannot interact with the physical order." Here was the response:
...
- 107