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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How I think about rolling [closed]

Below, I have written how I think about rolling. I wish to know if my idea as to how it works is correct. Consider a rigid ball on a plane which has considerable friction. If you push the ball ...
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68 views

How does rocket thrust work?

I can't seem to find a specific answer to this anywhere. I understand that in a rocket there is a chemical reaction that causes gas particles to leave the rocket at high velocity. By Newton's third ...
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41 views

Component of Component of a vector [duplicate]

NOTE : By perpendicular component of $\vec{F}$, I mean a vector which is a component of $\vec{F}$, but perpendicular to it. In the image above, the red vectors are a possible set of rectangular ...
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103 views

How to explain the force applied on this object? [closed]

Sorry for posting such a simple problem but I'm having trouble understanding this concept. In the picture below, we have a force, $ \vec F_{app}$ acting on two objects, A and B. Mass of block A: $ ...
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16 views

Kinetic Energy in the Center of Mass Frame

Given two bodies moving along a line, I can find the velocity of the center of mass frame. Taking the time derivative of the Galilean transformation I get $v'=v-v_{cm}$ By definition, the total ...
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48 views

Change in energy during orbital decay

Suppose we have a planet orbiting a star and the planet radiates away some amount of energy $\Delta E$. I want to find by how much the orbit decays (i.e the change in orbital radius). One way to do ...
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43 views

Will the Earth ever show synchronous rotation? Why and when?

In this answer to the question "why does the moon have the same rotation and revolution periods?", we read: The mass and speed of rotation of the Earth influence the moon in that some of its ...
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36 views

Motion under gravitational forces

In a system of particles, can a particle be considered to be attracted to the combined center of mass of the other particles if the Newton's universal law of gravitation is used (the inverse square ...
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54 views

Question about Kinetic Energy and Force acting on a body

Below is the graph of a body that rests on a friction-less flat surface. On this body force F is applied and it's value is being depicted in the graph below. We can see that the body moves from point ...
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78 views

Why do the masses in an Atwood's machine move?

The masses you see on the following picture are $m_1=8$kg and $m_2=12$kg. Also the coefficient of friction between $m_2$ and the floor is $0.25$. What i'm concerned with is that although $m_2 ...
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68 views

Confusion with Newton’s third law

Suppose i push a box with my hand which has a mass=1kg. I apply a force of 2 newtons and it will accelerate at 2m/s^2. But, according to the third law, the box applies a force on me, which is also ...
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55 views

Can a planet's orbit around a star be simulated? [closed]

Say I know all parameters like density, size, rotational velocity of a planet, could I predict its orbit around a star where I also know parameters of it? I want to design a simple model of the solar ...
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189 views

At What Point Does Mass Cease to Matter?

I know very little about physics so I naturally have a lot of simple minded questions. Assuming I am piloting a rocket and want to obtain the fastest speed possible. At what point does mass more ...
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101 views

Why can we assume, when dealing with tension, that the mass of a rope is $0$ but still assume that there are forces on it?

I started studying tension and I can't understand the following concept: If I have two objects $A,B$ collegated by a rope, where $A$ applies a certain force $\vec{F}$ on it, I would have that the ...
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3answers
72 views

Violation of Newton's third law

consider the following situation shown in the diagram below.A huge wall of mass M is moving to the left due to a constant force of 100N. Now suppose a man of mass m applies a force of 20N to the ...
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61 views

Rotational equilibrium Paradox

A block of mass M and height h is moving on a rough surface of coifficent of friction 0.5 .The block is moving with a velocity v at some instant. if we balance the torque due to frictional force and ...
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116 views

Force required to send ball in set trajectory

If I have a desired 2D trajectory where I know the desired speed of my ball and desired path, and a ball that starts at (x=0,y=0), how can I calculate the required force / point at which the force ...
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2answers
46 views

Tension at topmost point of a vertical circle

I read that for a body to move in a vertical circle, the minimum tension needed is 0 at the topmost point. Can someone explain to me what it means to have positive or negative tension on top. I'm not ...
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3answers
121 views

Why do objects move when you apply a force that's equal in magnitude to the friction? [duplicate]

If the friction on an object is 200 N and you apply 200 N, it seems, the forces should immediately cancel each other out since the friction and your applied force go in opposite directions, leaving ...
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48 views

Alternative method for pulley system not working

We have two a pulley system with two masses of 2kg and 3kg on two ends of a massless string. At the end of 5 seconds, the string breaks. How far up did the 2kg block move? Here's what I have tried:- ...
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50 views

The formula for the kinetic friction on inclined surface

I'm confused about the formula for the force of friction on inclined surface. It says that $f$ (force of friction) = $\mu N$ (where $\mu$ is the coefficient of the friction). Is: $$f = ...
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3answers
81 views

Prove that the spacetime interval is not invariant under Galilean transformations [closed]

The spacetime interval $(\Delta s)^2 = (\Delta x)^2 + (\Delta y)^2 + (\Delta z)^2 - c^2(\Delta t)^2$ is invariant under the Lorentz transformation and this isn't the case for the Galilean ...
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136 views

How are the watt-second, the newton-meter and the joule different?

The joule is $\mathrm{kg\,\ m^2/s^2}$ right? The watt-second is $\mathrm{J/s} \times \mathrm{s}$ thus $\mathrm{J}$. The newton-meter is $\mathrm{kg \,\ m/s^2} \times \mathrm{m}$ thus $\mathrm{kg \,\ ...
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94 views

Whether a large or a small ball fall faster in the air?

Given a ball falling under gravity is subjected to air resistance, after performing a differential to the drag equation, I get: $$g-Z(v^2)/r = a = v',$$ (where $Z$ is a constant.) How can I know ...
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501 views

Center of mass (COM) of a uniform quarter disk [closed]

I was trying to calculate the coordinates of the COM for a uniform quarter disk. By symmetry, it must lie on the angular bisector of the central angle. Also, $A=\frac{\pi R^2}{4}$, thus ...
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80 views

When to use a whole vector approach vs an energy approach?

My professor has just introduced two new ways to solve projectile motions. One approach involve using trigonometry and vectors and the other involves using the idea of conservation of energy. My ...
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298 views

How can Kinetic energy formula and the Work formula be derived without assuming the other to be true?

After searching how to derive the formula for Kinetic energy, I found that most derivations required the use of the "work" formula. After searching how to derive the work formula for a bit, I found ...
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235 views

Hooke's Law and Simple Harmonic Motion

Can anyone explain how the following formula is derived and what it means? $$x'' = -n^2x $$ I was reading through my high school physics textbook and I stumbled upon a section on Hooke's Law. It says ...
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74 views

Rocket velocity during fuel burn [closed]

I know the formula for the velocity of a rocket after the on board fuel has been used up: $$ \Delta v = v_{ex} \ln\left( \frac{m_i}{m_e} \right) - gt $$ where: $v_{ex}$ is the exhaust velocity ...
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5answers
254 views

What happens to the kinetic energy of a dropped ball when it comes to rest on the ground?

If we want to drop a ball from a height, we calculated that potential energy at bottom is zero and we say it is converted into kinetic energy. At that movement, if it is a kind of sand, we find it ...
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3answers
118 views

Can the anti-torque of a motor be used to spin a space vehicle about it's axis?

Imagine an electric motor together with its power supply in space. What exactly will happen to it if it is suddenly powered? Will it spin about its axis, or it will experience no motion relative to an ...
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81 views

Does a laser beam generate an equal and opposite force

If I hold a laser pointer and press the trigger does the emission of the beam generate kick-back in the opposite direction through conservation of momentum. I understand it would be tiny, so my ...
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3k views

Acceleration of a particle moving along a straight line

If a particle moves along a straight line, then can we say that the acceleration should be zero? and if not, then why? If the equation of the motion is linear, then the velocity is constant and if ...
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51 views

If I flex my arm, where is the “equal and opposite” reaction?

In my sight, nothing happens at all. Is the opposite reaction pressure applied to my bones? It certainly seems so; however, since I flex my arms in a curve, shouldn't the opposite reaction direction ...
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79 views

Feynman Lectures: Resonance - Problem with Formula

I am reading Volume 1 Chapter 23 of FLP, and I have come across something rather strange. Feynman says that: $$ \rho^2 =\frac{1}{m^2[(\omega^2-\omega_0^2)^2+\gamma^2\omega^2]} $$ A graph of this can ...
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76 views

Rigid body: internal work null?

I am following an elementary physics course book, namely W.E. Gettys, F.J. Keller and M.J. Skove's Physics (in an Italian translation). In exercises where no non-conservative force acts on a rigid ...
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454 views

Understanding Millikan's oil-drop experiment

This is quoted from A.P. French's Newtonian Mechanicsabout Millikan's oil-drop experiment: The droplets randomly produced in a mist of oil vapor are of various sizes. The ones that Millikan found ...
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254 views

Why do particles of equal mass (with one at rest) undergoing elastic collisions scatter at only right angles?

This is from the Section 9.6, page 351 of "Classical Dynamics of Particles and Systems" by Thornton and Marion. By setting a up a system where mass 1 has initial momentum $m_1 u_1$ and mass 2 is at ...
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102 views

Sun and planets orbit each other

Do not the planets and the Sun revolve in orbits around each other and the shape of the orbit depends on where the center of gravity of the system is? The greater the mass of the Sun, the closer the ...
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175 views

Variation in spring constant with respect to the length and no. of coils

Do the spring constant depend upon the length of the spring? No. of coils? Like what happens to the spring constant if you cut it in the half?
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249 views

Work done by friction on car

David Morin, in "Introduction to Classical Mechanics" says that friction does not exert a force on a car because the ground is fixed but that KE of the car is changing to internal kinetic energy in ...
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4answers
635 views

Gravitational force of a ring [closed]

Given a ring with mass $m_1$, radius $R$ and a point mass $m_2$ with distance $x$ regarding the center of the ring. How can I calculate the gravitational force of this ring ? At first glance I'd say ...
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1answer
2k views

The Coefficient of Restitution of a bouncing ball

If I drop a ball from a height $H$ and the ball rebounds from the floor it will bounce back up to a height of $e^2h$ where $e$ is the coefficient of restitution of the collision between the floor and ...
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543 views

Coriolis force on bullet vs airplane

Why do airplanes experience negligible Coriolis force while bullets experience the Coriolis force in long range shooting, even though the mass of airplane is much bigger than a bullet?
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397 views

Falling rope problem (disagreement with solution found at Problem Set)

On a frictionless table there is a homogeneous rope of length $L$ and mass. We push the rope such that it immediately starts falling due to gravity. Find the velocity when the rope has fallen of ...
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164 views

Would it be possible to make a space elevator only in the atmosphere?

I wonder if with current day technology we could make a "floating platform" which hangs from a satellite by a space elevator. This could allow a "launch process" involving floating a balloon to the ...
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443 views

Can there be friction unless the objects in contact are not acted upon by an external force?

The definition of friction I read from The book, General Physics written by Henry Crew is that, The resistance which either one of the body offers to the motion is called force of friction". If it is ...
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If the force of friction is 20 N for a moving body does acceleration increase with the increase of the mass?

A body is moving and the only force acting on it is the force of friction. If we put another body on this moving body somehow the force of friction will increase; does its acceleration change?
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How is it that Force = Mass $\times$ Length / Time ^2?

I understand how $F=ma$ but what I am looking for is a diagram, idiom or concept that explains how force can be explained (in a partial layman's terms) as a combination of the dimensions; Length, Mass ...
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233 views

Placing an object in a tub changes the weight of the tub?

Suppose you have a tub filled with water and it rests on a scale so you can measure the weight. If you place an object in the tub, will the reading on the scale change? Clearly if the object sinks ...