Questions tagged [forces]

This tag is for the classical concept of forces, i.e. the quantities causing an acceleration of a body. It expands to the strong/electroweak force only insofar as they act comparable to ‘classical’ forces. Use the [particle-physics] tag for decay channels due to forces and [newtonian-mechanics] or one of the other subtopics of [classical-mechanics] for the dynamics of classical systems.

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When I push a 24-karat gold bar with my finger, what subatomic physics are at play? [duplicate]

I chose a pure gold bar to eliminate the possibility of any chemical reactions occurring, the same question would apply to any everyday object like a wooden block or a marble. Or it could apply with ...
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Momentum transfer to dielectric thin slit array grating

I know that when light impinges on a planar slit array grating (say, dielectric transmission grating, equidistant slits), the light diffracts and breaks into orders. If the light changes its momentum ...
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Why do we consider the whole process, taking a single moment? Universality of the vector equation

I have considered a simple model for describing the elastic force vector of a spring. First, I chose a reference frame in an arbitrary way, then I drew the necessary vectors, we get a ratio that ...
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Can We Have 0 Normal Between Any Two Bodies Just Touching Each Other

I am a bit confused... Here if we see x-axis forces they are getting detached from each other. So To Resist them The Normal Should Be Zero. I am not sure if I am applying the right logic or not but ...
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Is there any such thing as a force quantum?

Consider two massive particles at a certain distance $R$ from one another in $\mathbb R^3$. The two particles attract each other through a certain interaction that decreases with $R$ : $F_{1\...
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Mechanics of ''Sumo'' vs Conventional Deadlift

A classic strength move (called the deadlift) involves bending over a heavy bar, holding it in one's hands, and then pulling it off the floor and standing up straight. Recently a variant called ''sumo ...
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Do I have the correct intuition behind the general dissipation function for Lagrangian Mechanics?

I am reading these lecture notes, section 2.7.1. The general dissipation function is given via a dissipative force: $$ \vec{F}^{D} = -\mu(v)\frac{\vec{v}}{v} \tag{2.269} $$ The Professors references A....
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How To Find Direction of Normal Contact Force?

I am a little bit confused. while doing questions I can see direction of normal forces are different. In Some Cases, It is perpendicular to the contact surface and towards the object on which normal ...
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Illogical conclusion about a mass on a spring [closed]

If you place a weight on a spring and it is an equilibrium, then you have this equation: $mg = kx$ you would solve for k and get: $k = mg/x$ but, if we used conservation of energy, assuming that when ...
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Why is a ball that is moving in one direction and spinning in the opposite slowed down if the force of friction is tangential?

If a ball has linear and angular velocity such that there is a slip between the surface of the ball and ground, why does linear velocity of the center of the ball decrease if the force of friction is ...
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How can there be a change in momentum with no appearent external force?

Momentum is conserved in a system with no external force. So then let's imagine a particle of mass m being dropped from the surface of Earth's atmosphere such that there is a significant change in G ...
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Can the electrostatic energy stored in a capacitor result in a net directional force?

This question references a concept in this patent, so I can understand if it's too specific, but it covers an interesting argument. The specific focus is on the math that's presented in the ...
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$F=ma$. $p = mv$. What's $mx$?

So I know that $$F=ma$$ ($F$ is force, $m$ is mass, and $a$ is acceleration). I also know that $$p=m\int a dt=mv$$ (Where $p$ is momentum and $v$ is velocity). So I was wondering if the following ...
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Derive the Law of Conservation of energy from Newton's 3rd Law of Motion

I'd like to derive a conservation principle for the mechanical energy, as sum of kinetic and potential energy, for a multi-body point mass isolated system using the $2^{nd}$ and $3^{rd}$ Newton's ...
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Optimising circular motion for high downforce vehicles

I'm doing a school assessment where i am trying to optimise the entry speed into a corner for an F1 car. With this there are a few assumptions for the sake of simplicity. entry speed = exit speed, as ...
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1 answer
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Is $F$ greater than the axial component of $f$?

It is assumed that the flow at the convergent nozzle outlet is constant. f is the force exerted by the convergent nozzle shell on the fluid in the nozzle. F is the axial force of upstream fluid to the ...
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Adding water into a container with water and an iron block inside [closed]

My question is directed towards the concept of buoyant force but to show it I have to examplify it with this A cubic block of iron of density 7.8g/cm³ and side L, floats in a container with water of ...
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7 votes
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Why do we always assume in problems that if things are initially in contact with each other then they would be like that always?

I am a high school student and I am confused in one thing:"Why do we always assume in problems that if things are initially in contact with each other then they would be like that always?" 1)...
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Inconsistency arising from a potential function that depends on time?

In a 1d setting, suppose we have the following potential: $V(x,t) = f(t)$ for some function $f(t)$. Notice that this potential does not depend on position $x$, it only depends on time $t$. It follows ...
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Doubt about Electromagnetic Attraction b/w Electromagnet-Iron vs Electromagnet-Electromagnet

https://www.supermagnete.de/eng/faq/What-is-the-difference-between-the-combination-magnet-magnet-and-magnet-iron At full contact, the attractive force between a raw magnet and an iron plate is the ...
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${}$Conservative and Non-Conservative Forces

For work done by conservative forces ($W = F.S$), we consider $S$ as the displacement and not the actual path travelled. However for non conservative forces we consider the total path length and not ...
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Why does static friction opposes force vector ...but kinetic friction opposes velocity vector?

MY ANSWER- lets say a body is on rest and a force is applied thats slowly increasing ....the tiny bumps and groves between surfaces will apply a normal until the force is big enough to break through .....
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How is work done by Tension zero in this case?

How is the work done by tension zero in this case. There is no horizontal force acting so the centre of mass won't displace in the horizontal direction as it will be in vertical. But the work done by ...
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Causality of pressure forces exerted by a roller when printing a woodcut block

I have been thinking about the causality of pressure that is applied by a printing roller onto paper over a woodcut block and how pressure forces might be conceived of. My first conception is that the ...
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How is Coriolis acceleration in polar coordinate, different from Coriolis acceleration due to observation in non-inertial frame of reference?

In Kleppner and Kolenkow's book: An Introduction to Mechanics, on page 34 (pasted below) on the topic titled "Acceleration in Polar coordinates", it has been mentioned that: "when $r$ ...
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Kinetic friction [duplicate]

Say we had an object moving at speed $v$ with only KINETIC friction (approximately $\mu$$R$) acting on it, I know that it will decelerate due to the net force and eventually come to a rest with $v=0$ ...
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How do I describe a disk that rotates on a rotating tripod?

I have a question about the following experimental setup: A cylinder stands upright on a table. This cylinder rotates around its axis. On top of this cylinder, a wooden disc about 3 cm thick is placed ...
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Strange behavior with candle and bin

In a corner of a room there is a window where there use to be wax and oil candles burning. Just below the candles, there is a bin. There is a lot of soot on the wall and the ceiling, but not over the ...
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How can we jump when the ground does no work on us? [duplicate]

This may seem like a silly question, but how can we jump when the ground does no work on us? When we jump off the ground, the ground does not move. This means the force from the ground on us does zero ...
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Standing up at 10% of the speed of light

Suppose I have a frictionless swing that is released from a height H m and I stand up after it has passed below the pivot at a height h m. If I stand up very quickly, say at 10% of the speed of light, ...
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Time dependent Dielectrophoretic force

I have been strugling in understanding the calculation of Dielectrophoretic force. I know there is a very frequently used formula (1): I can use this expansion if I have the formula of E However, ...
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Where would a string break if an instantaneous UNEQUAL tensile force is applied on the ends?

Similar to a question asked previously except this time with unequal tensile forces at the ends: Where would a string being pulled from both sides snap and why? Assume the string is homogenous. Would ...
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Energy and Force relationship

Is it right to think of Energy being what allows force(s) to happen? I know this is rather vague but is that a valid understanding?
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How to determine the extension of a spring? [closed]

The spring extended by $x\ m$, and the object moved downward from the mean position due to the force of gravity and reached an equilibrium. Find $x$. My attempt: I used a free body diagram to find $x$:...
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Does horizontal acceleration affect gravity?

If we apply 1G horizontally in some object, will this constant force equal to G affect the time of falling? If the force does not affect gravity, why gravity is prioritized over this force if both are ...
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Objects on inclined planes and the normal force [closed]

Say we had an object lying on a inclined plane, at an angle of $\theta$ to the horizontal, and the object has a mass of $m$. If we take the obejct to have an acceleration of 0 perpendicular to the ...
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Masses/spheres on a ring

Suppose I have a ring of radius R. And at the COM, two point masses of equal mass are placed. They're connected to the circumference with 2 massless rods such that they can move freely on those rods. ...
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What type of spring system can this system be treated as?

As we all know that when the springs are connected in series the tension is same throughout spring system collectively (elongation may differ in each spring if the spring constants of each spring are ...
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Distance a block slides along a surface with friction given with an initial velocity [closed]

For this part (e) of this problem, Source: https://ocw.mit.edu/courses/8-01sc-...647ea989a352a972dc4b3dfe_MIT8_01F16_pset7.pdf The solutions are, However, I don't understand why they only used a ...
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Scenario on the sign of hooke's law

Doubt is on the concept of the sign, not on the problem itself The main doubt is focused around the sign of $\vec{F}=-k\vec{x}$, and yes I've read a lot of posts on this page but it never ceases to be ...
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1 vote
1 answer
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Pressure at the bottom of a swimming pool [closed]

Why is atmospheric pressure it not taken into account when finding the force exerted by incompressible fluids onto a surface within the fluid? If you don't understand my question, then consider the ...
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Force and equilibrium

My book says that if a string was passed through a smooth ring the force of tension at each part of the string will be equal. And as it can be seen here the two parts aren't equal in length. So my ...
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Is work done against or, with the field?

Imagine you have a circuit with charged conductors. Electrons goes from this first conductor, to a second one. We would like to find out the charge of this first conductor. Using common sense, if ...
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What is the force of gravity on two particles? [closed]

Suppose that I have a system of two particles. They have the same mass $m$. At the origin O is something with a very large mass $M$ which is attracting the two particles. The first particle has ...
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Tension generated in a metallic loop placed in a time varying magnetic field [closed]

We have a metallic wire circular loop of resistance $R$, having radius $a$, placed in a magnetic field $\bf{\vec{B}(t)}$. The magnetic field is perpendicular to the plane of the wire. The magnetic ...
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1 answer
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Why is normal contact force electromagnetic in nature?

I learnt that normal contact force can be interpreted as the restoring force when an object undergoes deformation due to external stress, and it is perpendicular to the surface of contact. I also ...
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The force Interaction between two charge spherical surfaces [closed]

I have to solve the following problem: Two spherical surfaces with radii $\:R_1\:$ and $\:R_2\:$ and electric charges $\:Q_1\:$ and $\:Q_2\:$ respectively are placed in such a way that the distance ...
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1 answer
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Force on a dam with atmospheric pressure [closed]

For this problem, So they assume that the pressure at the top of the dam is zero instead of 1 atm. Therefore I wanted to try to take atmospheric pressure into account, Do you please know how to get ...
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Is hitting an obstacle half the size of my scooter wheel the same as hitting an obstacle half the size of my bike wheel?

I rode a scooter (the kind that you stand up and hold on to, with small wheels) and it didn't seem to handle bumps that would be minor if I was riding my bike. I was wondering if that is because ...
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How do sand balls retain their integrity for so long?

A friend showed me how to make sand balls at the beach, like shown here on this YouTube video. We were both wondering how they managed to keep their shape way longer than any other sandcastle bits. I’...
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