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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Moment of inertia of a disc with masses attached at the rim

Does the moment of inertia of a disc with some masses attached at the rim be the same as one without the attached masses? Or is it necessary to use parallel axis theorem to incorporate the moment of ...
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886 views

Normal reaction on wheels when car is taking a turn

I recently read in a book that for a car taking a turn on a horizontal surface, the normal reaction of the road on the outer wheels is always greater than the normal reaction on the inner wheels. ...
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287 views

Do heavier objects fall faster? [duplicate]

This question has been asked multiple times here and all over the internet yet I can't find a conclusive answer: Some claim that heavier objects do fall faster: Don't heavier objects actually fall ...
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643 views

Fluid Mechanics Piston Problem

The actual problem: A hydraulic car lift has a reservoir of fluid connected to two cylindrical fluid filled pipes. The pipe directly below the car has a diameter of 1.8 m. the pipe on which the ...
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96 views

Finding kinetic friction coefficient

A box is thrown up an incline with degree $\alpha$. the kinetic-friction coefficient is $\mu_k$. the body returns back to its start point. a. prove ...
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1answer
293 views

Why is body frame angular velocity nonzero?

This question is relevant to Euler's angles and Euler's equations for a rigid body. Why aren't $\omega_1$, $\omega_2$ and $\omega_3 = 0$ in the body frame? How can we measure $\vec\omega$?
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145 views

Paradox of angular velocity

For a torque-free symmetric top, the Inertia tensor has an inverse $I^{-1}$, and $L=I\omega$. Which implies that $\omega=I^{-1}L$. But since $I, L$ are constants, $\vec\omega$ is a constant. However, ...
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2answers
219 views

Pressure in fluids

Fluids exert hydrostatic pressure because their molecules hit each other or the immersed body, but why is that at a greater depth pressure is higher when molecules are the same ? Assume density of ...
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3answers
274 views

Does the ceiling fan make the air and dust spiral in?

Does the rotation of ceiling fan makes air circulate in a spiral, circular motion beneath the radius of fan or the air from outside is also mixed with it and replaces the air in room? A ...
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0answers
652 views

Elastic Ball Collision and contact angle

For a project I need to make a good simulation of balls moving around in a space. The project will be without any air drag and without losing energy in bounces. Since there is no way to lose energy ...
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1answer
79 views

Why does a particle fall in a straight line?

In Lagrangian Mechanics we choose the path of least action. Given a uniform gravitational field, and a particle of finite mass; and fixing two points the start & end-point we consider all paths ...
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3answers
285 views

Will an object resting on a rotating platform move in a frictionless world?

Imagine that a pebble is placed on a uniformly rotating, frictionless disk. What will happen to this pebble? Will the disk slide under it and the pebble stay as is? Or will there be a centrifugal ...
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5answers
4k views

Difference between torque and moment

What is the difference between torque and moment? I would like to see mathematical definitions for both quantities. I also do not prefer definitions like "It is the tendancy..../It is a measure of ...
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1answer
554 views

Rod slipping against block due to gravity? [closed]

A uniform rod of mass $m$ and length $l$ is pivoted at point O. The rod is initially in vertical position and touching a block of mass M which is at rest on a horizontal surface. The rod is given a ...
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1answer
573 views

Newton's second law, gravity and buoyancy [closed]

A body of mass $m$ and volume $V$ is immersed into the sea. The body moves under the action of two forces: gravity and buoyancy (Archimedes). Gravity force has a magnitude $mg$, where $g$ is a ...
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1answer
266 views

Integration on a general equation for instantaneous angular acceleration

An equation for instantaneous angular acceleration is given as: $$ \alpha \equiv \lim_{\Delta t\to0}\frac{\Delta \omega}{\Delta t} = \frac{d\omega}{dt} $$ The text I am reading says writing this ...
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7answers
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What is the proof that a force applied on a rigid body will cause it to rotate around its center of mass?

Say I have a rigid body in space. I've read that if I during some short time interval apply a force on the body at some point which is not in line with the center of mass, it would start rotating ...
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2answers
4k views

When does not Newton's 3rd law apply?

Is Newton's 3rd law valid in non-inertial frames? If so, then are there other cases for which Newton's 3rd law is not applicable?
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8answers
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How do you explain spinning tops to a nine year old?

Why don't spinning tops fall over? (The young scientist version) My nine year old son asked me this very question when playing with his "Battle Strikers" set. Having studied Physics myself, I am very ...
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1answer
206 views

Ball on a slope [closed]

I have a lab report, but I can not write it in a correct way. The lab experiment was about a ball rolling on a slope, I have a height of the slope, the distance, and the time in which the ball spent ...
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2answers
2k views

Normal force and reaction

It is said that the normal force comes into play any time two bodies are in direct contact with one another, and always acts perpendicular to the body that applies the force. This force is a ...
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4answers
5k views

Dependence of Friction on Area

Is friction really independent of area? The friction force, $f_s = \mu_s N$. The equation says that friction only depends on the normal force, which is $ N = W = mg$, and nature of sliding surface, ...
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2answers
95 views

Work and energy problem [closed]

I am trying to solve the problem (see image), my concern is about the 2 factor, can anyone please help me understand this.
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1answer
1k views

Ski Jumper's vertical velocity after $246.5m$ record?

What would be the vertical velocity of this ski jumper (ski flyer), after he first touches down, after he breaks the record with a $246.5m$ jump? What g force would he experience as he slows down? ...
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1answer
437 views

Will a free-falling rod (without drag) rotate?

When we consider a bicycle is turning on a flat plane, we know that there is friction, which provide centripetal force on the bicycle. And we know that the bicycle is no longer perpendicular to the ...
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1answer
137 views

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 $\mathbf{x}_A(t)$, ...
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2answers
217 views

Tension in vertical circular motion

In vertical circular motion we conserve energy for calculating velocities at a point (if initial velocity given). But, energy can only be conserved when forces are conservative. Tension is not a ...
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1answer
1k views

Tension on either side of a massive pulley?

When a pulley has mass, why is tension on both the sides different? Why don't we consider rotation of pulley when it is massless?
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3answers
233 views

Finding the equation of motion of anharmonic potential [closed]

If I have a potential given by: $$U=U_0\left[2\left(\frac xa\right)^2-\left(\frac xa\right)^4\right]$$ It says that at $t=0$, the particle is at the origin ($x=0$) and the velocity is positive and ...
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2answers
225 views

Can a massless rope accelerate?

Suppose I have an Atwood machine, that is, two different masses connected with an inextensible, massless rope over a pulley. Assuming no friction between the rope and the pulley, the heavier mass will ...
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2answers
592 views

Why do orbital speeds decrease further away from the focus?

Why do orbital speeds decrease further away from the focus? A simple question, but I want to make sure I am understanding this correctly: Is it ONLY a function of the gravity well? As in, the ...
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1answer
159 views

The circumference of the Moon's orbit around the sun?

I know that it orbits the sun in what looks like a 12 sided polygon with rounded corners. But I can't seem to find the radius/circumference anywhere.
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2answers
154 views

Maxwell's demon - scaling down from something that seems to work

[I have updated the below description to clarify that the mechanism does not depend on a truly frictionless implementation. Also, since 2 commenters apparently assumed that I was proposing a ...
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1answer
364 views

D'Alembert's principle

Actually I have some troubles to understand what this principle is all about, so I want to use the simple pendulum in order to get the idea. Since I have read a few passages that dealt with this ...
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5answers
904 views

Person Pushing a Block vs. People Pushing off Each Other - Newton's Third Law

I have read so many forums on this and I still do not understand and it's affecting my ability to move forward with learning physics right now. Imagine the following scenario: a person on a ...
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2answers
1k views

What causes a force field to be “nonconservative?”

A conservative force field is one in which all that matters is that a particle goes from point A to point B. The time (or otherwise) path involved makes no difference. Most force fields in physics ...
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1answer
1k views

How Can force exist without acceleration?

From what I understand acceleration does not cause a force, but rather forces cause acceleration, so if I have a ball moving with CONSTANT velocity, that hits a wall, then the wall must apply a force ...
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1answer
109 views

Confusing Classical Mechanics Question

I don't want this to be a "do my home work question" so please tell me how I can make this question helpful for other people. In my physics assignment I found the question below. I'd think that both ...
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1answer
503 views

Condition for circular orbit

I am a little confused about the condition for circular orbit. Goldstein's Classical Mechanics has the condition for circular orbit as $$f'=0\tag1$$ where $f'$ is the effective force. I understand ...
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2answers
221 views

How is it possible to move something without completely lifting it?

For example, let's assume a chair here: It can be "slid" across the force if we use minimal upwards force, but not enough to actually "lift" the chair. Why should it move? Here's a better example: I ...
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2answers
357 views

Force acting on an object?

You have a bar of metal in an environment with no gravity. A force is applied on one end of it. How does it rotate? There is a non-zero torque on any random point selected on the bar. For example, ...
2
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1answer
248 views

Is there a better, faster way to do this projectile motion question? [closed]

The question is In a combat exercise, a mortar at M is required to hit a target at O, which is taking cover 25 m behind a structure of negligible width 10 m tall. This mortar can only fire at an ...
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1answer
589 views

Bouncing Ball Pattern

If a ball is simply dropped, each time a ball bounces, it's height decreases in what appears to be an exponential rate. Let's suppose that the ball is thrown horizontally instead of being simply ...
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1answer
244 views

In a game of tug of war, what concepts are involved in determining where the rope breaks?

Assume that in a game of tug-of-war the rope ends up breaking. What concepts/factors would contribute to the position of where the rope breaks?
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2answers
232 views

Internal/Rotational angular momentum

I have some difficulties to understand the relation between the internal and the rotational angular momentum of a rigid body which is also known as König's theorem, so what physical intuition lies ...
1
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1answer
1k views

Calculate Mass based on Velocity and Acceleration

I am attempting to design a obstacle avoidance system with the Arduino. My position (for now) is going to be stationary. I will be detecting an incoming object and I want to use the below known ...
6
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1answer
571 views

Meaning of the word “Moment”?

This question is more of a question about the origin of a physical term moment used in many contexts. My question is about the linguistic or historical meaning of the word "moment". Please don't ...
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0answers
93 views

Do vortex tubes work with a reversed end plug?

Would a vortex tube still work if instead of a cone plugged into the 'hot' end you had a smaller hole on the 'cold' end? As I understand it, the point of the cone on the hot end is to only allow the ...
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2answers
230 views

Scaling: Gravity and Friction

I understand how doubling the length of a shape quadrupes it's area and the analog in 3 dimensions. My question however relates to other physical quantities, for example gravitational field strength. ...
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2answers
185 views

Is mass proportional to the displacement from equilibrium in Hooke's law?

If I look at Hooke's law as it's defined in my textbook, it looks like: $F = -k\Delta s$ Therefore, the restoring force of an ideal spring will be proportional to the displacement from equilibrium, ...