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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346 views

Pendulum water pump - apparent free energy

I've seen plans for a pendulum oscillator water pump that is claimed to pump a large volume of water (100 gallons) from a well of 100 feet deep. The pendulum consists of a 100 pound weight raised 6 ...
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1answer
212 views

Block Sliding Down a Plane (Perpendicular Velocity)

I'm having trouble understand the concepts for this problem. Here's the problem: A block is placed on a plane inclined at angle $\theta$. The coefficient of friction between the block and the ...
3
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2answers
183 views

How does Kepler's laws and Newtons universal gravitation for two bodies come together?

Does Newton's laws of gravitation and Kepler's laws give exactly the same orbit for two bodies? Could someone please explain the derivation if so?
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1answer
401 views

What if the Earth stops in its orbit and instead falls straight towards the Sun? [closed]

The Earth orbits around the Sun because it has angular momentum. If we stopped the Earth in orbit and then let it fall straight towards the Sun, how long would it take to reach the Sun in seconds? ...
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3answers
194 views

Why does centre of mass of ice-container system shift in absence of any net external force?

Consider a cube of ice in a flat based container(the base is very broad).The temperature of the system is at first fixed at a minus Celsius temperature, but then the system is left on a table with the ...
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2answers
320 views

Motion of charge in magnetic field with drag force [closed]

Say you have a charged particle in a region that contains a fluid that will produce a drag force that goes as $F=-kv$ where $v$ is the speed and $k$ is some constant. The region also contains a ...
1
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1answer
66 views

Ask an equation to solve the next location of an object?

It is a long time that I have not learnt physics. But now I really need an equation to solve a problem. I appreciate physicists give me a little hint. Here is a object on the desk without friction. ...
2
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1answer
120 views

Infinitely many soft photons from pushing an electron?

I have been looking at some of the archives here and seen it quoted by Ron Maimon , that pushing an electron with a classical field means the electron will produce infinitely many soft photons should ...
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2answers
379 views

Increase in velocity by loss of mass? [closed]

A trolley of mass 300kg carrying a sand bag of 25kg is moving uniformly with speed of 27km/h on a frictionless track. After a while, sand starts leaking out of a hole on the floor of the trolley at ...
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0answers
86 views

How to show that a general Galilean transformation in three dimensions is a conformal transformation?

Suppose two particles with equal mass move and then collide. We can easily show that the angle of collision is ninety degree if we choose our frame of reference moving with velocity equal to one of ...
2
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0answers
90 views

Jacobian matrix of Galilean transformation

If we want to transform to another inertial frame of reference using Galilean transformation in 4-dimensional space-time, what is the Jacobian matrix of Galilean transformation?
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3answers
69 views

Why isn't the gravitational acceleration taken in to account when determining the net acceleration of a person riding a Ferris wheel?

Say for example you have a person riding a Ferris wheel. What is the difference in his acceleration (towards the center) for when he is at the highest point to when he is at the lowest point? So the ...
5
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1answer
159 views

QED and Newton's 3rd law

According to some lecture notes on propagators (see bottom of page) the Feynman particle/anti-particle hypothesis states: The emission (absorption) of an antiparticle of 4-momentum $p^\mu$ is ...
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1answer
118 views

What stops the car?

Centre of mass of a system cannot change its state of motion, unless there is an external force acting on it. Yet the internal force of brakes can bring a car to rest. Then what stops the car?
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3answers
126 views

Velocity vector for constant acceleration in newtonian mechanics

If the acceleration vector of an object remains constant, is there no change in the direction of the velocity vector? The question applies to any movements in classical physics.
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1answer
202 views

Newton's second law for rotation

Can the second law of motion for rotation, $\vec{\tau}=I \vec{\alpha}$, be used for any axis? Is there any case that acceleration $\vec{\alpha}$ is not in the direction of applied torque ...
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2answers
87 views

Components of forces?

Let's say we have an object lying on a slope, the weight of the object can be divided into two components one horizontal and one vertical. My question is does the weight act only in these two ...
2
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1answer
122 views

Event horizons in Newtonian mechanics and Galilean relativity

I've been revisiting classical physics (in the sense of Newtonian mechanics and Galilean relativity) and I was thinking why can't we have an event horizon in classical physics? Is it because the ...
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2answers
70 views

What will happen to a compressible fluid filled inside a sealed container when the container begins to accelerate?

Assume the fluid to be air and the container to be a car, will there be a pressure gradient which will result the fluid to stack at one end of the car or there is something else that I'm missing?
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1answer
173 views

Rotation of bodies about centre of mass [closed]

Imagine two masses connected by a massless, inextensible string kept on a smooth, horizontal plane. Now suppose one of the masses is given a velocity perpendicular to the string. So the masses will ...
8
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1answer
186 views

What is the optimal burn direction to lower periapsis of hyperbolic orbit?

I am an engineering student who is interested in orbital mechanics. I am doing some self study before taking some orbital mechanics courses next year. I was learning about various orbit types ...
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1answer
71 views

Reduced charge for attracting electrons?

The reduced mass in the two body problem is $\mu= \cfrac{m_1 m_2}{m_1 + m_2}$. Is there any analog to this with interacting charged particles (or at least that is of use somewhere in physics)? I have ...
3
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2answers
237 views

Velocity and acceleration in SHM

Can velocity and acceleration reach maximal values during the SHM simultaneously? Can you explain why?
-1
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2answers
133 views

Friction acting on mass on string

Assume we have some stationary point mass that would slide, if not for some coefficient of friction, along a light, inextensible string, attached to two points at different heights. Considering ...
1
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1answer
473 views

Proof that the ground pushes you up [duplicate]

It has been said that when you try to jump you are exerting your force on the ground and the ground pushes you up. I was wondering if this was an over-simplification or not. If so, what's the full ...
16
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5answers
783 views

Conservation of Mathematical Constraints when deriving Energy and Momentum from $F=ma$

Background: Starting from $F = ma$, integrating with respect to time, and using basic calc, one can derive $\int Fdt = m (v_f - v_i)$ Starting from $F = ma$, integrating with respect to distance, ...
3
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2answers
639 views

Car on a frictionless banked curve

A car is on a banked curve, following a path which is part of a circle with radius $R$. The curve is banked at angle $\theta$ with the horizontal, and is a frictionless surface. What is the speed ...
1
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1answer
399 views

Pressure difference in u tube

Suppose you have a U tube filled with a liquid. The height of the liquid column in both the arms of the U tube is not the same. Will the pressure be the same at two points in the two arms of the U ...
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2answers
105 views

A revolving astronaut

The concept of orbital velocity tells us that there must be a minimum velocity for a satellite to revolve around earth and the velocity should be such that the gravitational force of earth provides ...
6
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2answers
394 views

What's the difference between work in thermodynamics and mechanics?

What is the difference between work in thermodynamics and work in mechanics?
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4answers
1k views

Can a particle have momentum without energy?

Can a particle have linear momentum if the total energy of the particle is zero? Even if a particle has a certain velocity, can its potential energy cancel out the kinetic energy as to add to zero ?
2
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1answer
100 views

Do I need to take elastic potential energy into account? [closed]

Let's say I have a vertical spring with end points $A$ and $B$ and length $a$ and a mass attached to the endpoint $B$. The mass is dropped from the point $A$ and I need to find the kinetic ...
4
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1answer
250 views

If friction disregard area, why the direction you drag a long object matters?

I am talking here about dry friction between solid objects, for example a ruler and a table, not anything lubricated or fluid. I noticed that with a ruler and a table for example, if you drag the ...
3
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2answers
108 views

Relationship between mass preserving four-fources and proper acceleration

Background I studied Rindler's book on Relativity. Relevant information from this book is available on-line here: http://www.scholarpedia.org/article/Special_relativity:_mechanics Given that we ...
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0answers
273 views

Work done by rolling vs skidding friction force

Two identical bicycles having equal weight riders are traveling along a level road adjacent to each other with the same non-zero velocity. Bike A, (the "skidder"), applies the rear brake strongly ...
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0answers
73 views

maths question on levers [closed]

Someone holds a 2kg weight in their hand at a distance of 35cm from the elbow (fulcrum) and the downward force (load) due to the weight is 20 Newtons. Calculate the effort in Newtons that the ...
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2answers
63 views

A block in motion explodes [closed]

A 9.5 kg block (A) is traveling in the positive x-direction with a speed of 3.0 m/s. At some point, it explodes and breaks into two pieces. After the explosion, block C, which is 6.0 kg, moves off ...
0
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1answer
136 views

Centrifugal force in inertial reference frame [duplicate]

Take for example the case of a rod rotating about an axis passing through its centre of mass and perpendicular to it. It has a ring hung from one of its sides. The rotation of the rod causes the ring ...
0
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1answer
161 views

Speed of ejection of liquid from revolving tank

Consider a cylindrical tank filled with a liquid. Suppose it has an orifice somewhere at the bottom and the liquid is spurting out of this hole at a certain velocity. Now, if you rotated this cylinder ...
2
votes
1answer
457 views

Spring system - 3 DoF system and its properties while changing stiffness

I was given the attached 3 degree of freedom spring system with the purpose of analyzing it. I came up with the following equation of motion and then I ran Matlab to calculate the corresponding ...
-1
votes
1answer
89 views

Perceived sway difference between double-decked vs. single-decked buses?

Why is that when I'm standing in a moving double deck bus, my body doesn't move a lot; whereas, in a moving single deck bus, my body moves quite a bit? It seems like I swing a lot in single deck ...
2
votes
1answer
161 views

Definition of Lorentz transformations as transformations of the universe?

Following Arnold's [1] definition of the universe as an affine space $ A ^4$ with the group $\mathbb R ^4$ acting on it, we may define a galilean transformation as an affine map $g:A^4 \to A^4$ which ...
2
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2answers
232 views

Higher moments of the kinetic energy operator in QM

I have set myself the task of studying the kinetic energy $T$ in a quantum mechanical system. For the latter, I use the simple case of the Hydrogen atom in the $n=1$ state. Then the wave function is ...
0
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1answer
72 views

Find the force used to press a book against a leaned desk so it doesn't slip

I know there are several threads concerning this issue, but none of it helped me, so I decided to open a new one. So, the task is to find a force $F_{\mathrm{push}}$ on a desk which is leaned for an ...
4
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3answers
171 views

Do bullet/gun physics change if the gun is traveling very fast?

If I'm running at say $400\: \mathrm{m/s}$ and a bullet travels at $400\: \mathrm{m/s}$ and I fire the gun, will I see the bullet leave the barrel? I either see it stay in the barrel floating ...
0
votes
1answer
149 views

How do I find angular and linear velocity after normal force and “infinite” friction force?

Look at this picture: http://i.imgur.com/mY8ShkV.png Here we have a ball resting on top of a platform (the contact point is marked red). I know the normal vector (marked green). I also know the mass, ...
0
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1answer
222 views

Container of liquid in free fall

Imagine a container of liquid in free fall. Why does the liquid fly out of the container. Is there a force exerted by the inside fluid on the surface of liquid which causes this? Also, suppose there ...
0
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1answer
81 views

Oscillation Question [closed]

Now normally (if it was a block not rotating) all you would have to do is use $w^2 = k/m$ and $E= \frac12k(A\cos(2wt+\theta))^2 + \frac12m(Aw\sin(wt+\theta))^2$ or in other words the translational ...
1
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1answer
198 views

Is There Any Work Done By Normal Reaction Force even if point of application of force is not getting displaced?

Suppose that I am standing on the ground and I suddenly jump and rise up to any certain height.So accordingly I would have gained some speed i.e. Kinetic Energy during the process of jumping.According ...
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2answers
153 views

How to find time, acceleration under this situation

I am trying to solve the following. An object of mass $m$ slides on a horizontal surface with initial velocity $v_0$. If the kinetic friction between the object and mass is given by $\mu$, find ...