# Questions tagged [newtonian-mechanics]

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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### Should the coin be heavier or lighter in the coin drop experiment?

The Coin Drop experiment is a classic experiment used to demonstrate Newton's First Law of Motion. In this experiment, a glass is covered with a card and a coin is place on the card. The card is given ...
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### Why does the derivative become $x=r\dot\theta\cos(\theta)$ when calculating angular velocity?

This is not a homework question because I do not want help with solving my homework. I would rather want an explanation of why the derivative of this seems to break math as I know it. Background ...
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### Why does water flow downhill?

Researching this topic, I found everyone just saying because of gravity. But that makes no sense to me. Gravity exerts a downward force: But water flowing downhill goes sideways. There must be a ...
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### Elastic Collisions - Equation not working?

This is the question: When cars are equipped with flexible bumpers, they will bounce off each other during low-speed collisions, thus causing less damage. In one such accident, a 1850 kg car ...
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### Centripetal and Centrifugal acceleration/force [duplicate]

Centripetal force acts towards the centre and necessary to keep an object in circular motion. But centrifugal force is equal to the magnitude of centripetal force and acts in outwards direction and ...
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### Dynamics collisions - reduced mass [duplicate]

In dynamics when doing collisions from the centre of masses' frame of reference we use reduced mass. What is is it and why do we use it?
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### Why are gravitational mass equal to the mass in Newton's second law [duplicate]

Newtons second involves the mass $m$ e.g. $$F = m a$$ And the gravitation force also involves the mass e.g. $$F = - G \frac{m_1 m_2}{r^2}$$ The question is why the gravitation mass is equal to ...
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### Conservation of energy when ball rebounds

Consider a ball that strikes a stationary box and has momentum $mv$. If the ball rebounds with the same speed it had before the collision, its momentum is $-mv$. Therefore, the box must have a ...
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### Is Newton’s gravitation law able to explain the circular motion of the earth around the sun?

I have read in Forbes website that the orbit of the earth around the sun is expanding (by 1.5 cm in 2019). I have also heard that big bang theory suggests that the universe would collapse into ...
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### Mean free path equation derivation

I was reading about mean free path equation derivation online and stumbled upon this: We will derive the equation using the following assumptions, let’s assume that the molecule is spherical, and ...
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### Is Newton's first law an “If and only if”

On Wikipedia, Newton's first law is stated as: In an inertial frame of reference, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force. I read ...
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### Does universal proof exist for newton's experimental law for all cases of elastic collisions?

Newtons experimental law I. E velocity of approach is equal to velocity of separation (for the points on the two bodies where the collision takes place) for an elastic collision is applicable for ...
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### Tension at lowest point: oberbeck pendulum

I'm solving a problem involving oberbeck pendulum We are given $M$, $m$, $r$ (radius of pulley), $R$ (distance from center of rotation to each of the 4 small weights). The problem says that the ...
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### Nobel Prize in Physics 2019 on exoplanets and Hot Jupiters

The 51 Pegasi b, discovered by Didier Queloz and Michel Mayor is classified as a hot Jupiter and not considered to be a star. I had read a bit about the minimum mass necessary for being a brown dwarf ...
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### Why do we differentiate displacement to get velocity if displacement is given as a function of time [closed]

Like if the displacement is given as S=(2t³)and if we are asked to find the velocity in 2 seconds then if we put t=2 in the expression we get 16 which isn't correct. The correct must be dS/dt=6t² and ...
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### Is it normal to assume equal impact time?

If we have two hammers of different weights both hitting an object with the same force can we assume they both have the same impact time?
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### Objects slowing down

I know that when an object is moving on a suface it slows down due to friction , now since the kinetic friction on the object is constant (and it's the net force on the object since the normal force ...
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### Which road will have less wear and tear of tires, a concreted or a tarred road?

I am wondering that where could be more friction, whether on a concreted road or tarred roads. My question is that which road will have less wear and tear of tires, the concreted or the tarred roads?
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### Advisory speed limits on turns

I was just thinking about why many corners have advisory speed limits that are less than the highway speed limit, does it have to do with centripetal acceleration?
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### Understanding Vis-Viva equation

I have seen two different forms of the vis-viva equation: \begin{align} v^2 &= GM\left( \frac{2}{r} - \frac{1}{a} \right) \tag{1} \\ v^2 &= G(M+m)\left( \frac{2}{r} - \frac{1}{a} \right). \...
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### Circular motion and banked roads question

I can't work out c) for the following question, and I'd just like some help clarifying why my solution is wrong. Part a) and b) are fine. A car rounds a bend on a road that follows the arc of a ...
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### On understanding the relation between Heisenberg Uncertanity Principle, Indeterminism and classical chaos

I recently read Emperor's New Mind by Roger Penrose. In it he talks at length on the notion of determinism in science. In this context how does the Heisenberg Uncertanity Principle bring about the ...
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### Friction on Parallelepiped

Is the friction on a parallelepiped with mass m equal to the friction on a dice with the same mass? Because the overhang of the parallelepiped causes an irregular distribution of the normal force on ...
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### Role of friction during Collisions

Normally, in questions of collisions, we tend to apply conservation of momentum (and in cases of elastic collisions, conservation of energy as well) and we usually ignore the frictional force acting. ...
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### Acceleration-time graph for a falling object

I understand that when drawing an acceleration-time graph for a falling object (with initial velocity = 0), the y-intercept should be $9.81ms^{-2}$ and acceleration should end up being $0ms^{-2}$ as ...
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### Question on flywheels and angular momentum [closed]

I've recently been exposed to gyroscopes in my physics class. We discussed flywheels in relation to the gyroscopic effect. I was wondering how the stationary flywheel scenario worked. Why is it that ...
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### Electron volt $eV$?

$1 eV$ is defined as the energy gained by an electron when accelerated through a potential difference of $1V$. But, I think when the electron is accelerated, it gets closer and closer to the source of ...
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### Which approach to take with a vertical spring?

Lets say we have a spring hanging vertically with spring constant $k$ attached to a block of mass $m$. The system is at rest. Then, you pull the mass downwards, extending the spring by distance $x$,...
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### Newton's 3rd law in lami's theorem

I'm a high school physics student dealing with the following problem: Despite solving the problem correctly, I don't understand the diagram (b) supplied with the problem: These are my questions: ...
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### What is torque, really? and can it be determined for a point on a circle that is away from the center of the rotation axis by a radius $r$?

Let's picture a Rolling without slipping Wheel, that constantly accelerates. radius of a wheel/circle is $r$. Basically any wheel of a vehicle is rotating around its fixed axis - AoR -(axis of ...
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### Distance traveled by a particle in $n^{th}$ second

My book states that the distance traveled by a particle thrown upward in the last second is independent of it's initial velocity because the the object travels the same distance as a freely falling ...
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### Understanding newtonian gravity

In gravitation that two object mutually attract applying equal forces on each other. But for instance if we take a disc and a solid sphere the fact that they have different gravitational fields on on ...
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### Is projectile angle for farthest distance same for human arm?

A projectile, in other words, travels the farthest when it is launched at an angle of 45 degrees. But human arm's velocity may vary at different angle, so angle for farthest distance may not be 45°.
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### Calculating Mass of a block in this pulley block systen

This question was asked in My Viva- Consider this pulley block system.This system is equilibrium in equilibrium . Now assuming string to be non elastic this would imply M1= M2 (as tension is uniform ...
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### Why do we feel weightlessness during free fall?

An object in free fall accelerates towards the Earth at a acceleration equal to $g$ (the accleration due to gravity). Now if we ignore the air resistance, why do we feel weightlessness? I could not ...
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### Calculating force changes from single hanging system to a pulley

In modifying an indoor clothes drying way (after laundry), I simplify the problem as follows: A single hanging system as shown (before). The point bearing stress is P. It hangs 100 lbs of weights. ...
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### Finding the Parametric Path of a Particle in a Force Field

This question arose when I was doing some work with line integrals over force fields. In these questions, the reader is always given a parametrization of the particle's path (in terms of time) and ...
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### I have this problem in my physics homework. How far does the box travel along the ramp on its way up? [closed]

You are using a spring to launch 2kg boxes up a ramp. The spring has a spring constant of 500N/m and is compressed 50cm before launching each box from rest. You notice that there is a 1.5m long patch ...
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### Is the continued rotation of the ball due to inertia?

I think the rotation of the ball is due to the inertia of the ball, because when there is no external force, the ball will continue to rotate. But some people think that the rotation of the ball is ...
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### Do pseudo forces create a field?

Suppose i am travelling in an accelerated car (with constant acceleration), would there be a vector field in the space i view due to the pseudo forces? If yes what would be its nature and would it be ...
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### This is a question based on Newton's laws of motion.I couldn't even get an idea about it [closed]

A heavy cylindrical shaft of massM is vertically through a distance s into the ground by the blow of a pile driver of mass m.the pile driver drops vertically through a distance h onto the head of the ...
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### How can I verify the relation $m\omega^2 = |\textrm{constant}|$ using logarithmic plot? [closed]

We have demonstrated the uniform circular motion in the lab. Centripetal force and the radius are constant while the mass of the object increased 5 times thus 5 different angular velocities were ...
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### Is energy more fundamental than force? [closed]

I was wondering, there are several examples where energy comes in very handy. Many problems in kinematics which are really challenging if you could use only forces, can be solved effortlessly by ...
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### Why do all observed stable $n$-body systems have the largest mass at the center?

Comparing three different scales of $n$-body systems, atomic systems, solar systems and galactic systems, we find that all (observed) systems that exhibit long term stability have the largest mass at ...
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### What is mean by the statement that constraint forces do no work?

Consider a system consisting of two particles of a given mass, floating in space, aligned horizontally, constrained to remain at a fixed distance from each other by a massless thin rod (or string). If ...
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### Object motion in air (with air resistance) [closed]

We should create an object motion model. We have such information: $\overrightarrow{v}$ - object's basic velocity; $m$ - object's mass; $\overrightarrow{F}=|v|^2k$ - the law of air ...
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### How can kinetic energy increase during a collision?

The below homework question just sets the context for my question. I am not asking for a solution to this question In a collinear collision, a particle with an initial speed $v_0$ strikes a ...
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### How is the external force and the tension force related in this system [closed]

Two bodies, A and B, are connected by a string. The string is massless, inextensible, and is always tight. Also, the surface they are on is frictionless. There is an external force $F_{applied}$ ...