# 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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### Force of adhesion of polystyrene microspheres to glass surfaces

I am currently working on determining the force with which polystyrene microspheres suspended in water would adhere to a glass surface. To ensure that my methods would give correct results, I would ...
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### Force from Water Entering a Pressurized Tank with No Relief Valve

I am trying to understand how a force at the opposite wall from water entering a pressurized air tank (atmospheric pressure) with no relief valve to displace the compressed air can be deduced. I have ...
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### If there is an upward normal net force when an elevator is going up, then shouldn't I be floating as an impact of the upward force?

When an elevator goes up, the upward normal force of a person standing in the elevator increases due to the acceleration of the elevator. As a result, there is an upward normal net force. So, shouldn'...
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### Friction and Newton's Laws

The below figure shows a tower built by placing many rough books one on another. The coefficient of friction between each book is $\mu$. What is the minimum force required to pull the $n$-th book ...
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### What is the meanings and relation of electron negative charge from Coulomb Law perspective

Electron is defined to have negative charge. From many questions we can see here in Stack Exchange we conclude that charge is a property of a particle in an electromagnetic field. But as we learning ...
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### Are there two normal forces here?

In this question the normal force direction on the collar was determined to the left, while there is a possibility to be to the right direction also since the collar contacts the rod in both ...
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### The purpose of leg drive in the bench press (force body diagram)

A common explanation I've heard for the purpose of the leg drive in the bench press is that the lateral forces generated by the quads off the floor are "converted" into a downward force into ...
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### Tension In circular motion

In the below question is given 2 scenarios in which we have to find the tension in two particular cases, A ball is held at rest in position A by two light cords.the horizontal cord is now cut and the ...
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### Is passive magnetic levitation without moving parts possible without the use of diamagnets?

So, I looked at the Wikipedia page on magnetic levitation and it described lots of ways of levitating things magnetically, but they were all stabilized by either electronic feed-back loops, ...
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### What exactly is force? What is its source or origin?

I am asking this question here after trying to do much research and study to understand it on my own first. I am not sure if I am asking a metaphysical question that really can't be answered in ...
1k views

### Is there any fundamental reason why acceleration is a linear function of external forces?

Perhaps a trivial question, but it is something which I couldn't ever grasp ever since beginning physics. Why exactly should Newton's second law be linear in application of all the external forces? ...
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### Torque on a rod rotating in free space and it's motion

Let us consider a rigid body consisting of two particles of mass $m$ at either end of a rigid massless rod of length $2l$. Suppose that the rod rotates in free space with angular momentum $Ls$ along ...
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### How is energy lost?

I can understand that if force is applied in the same direction as the motion of the object, energy is transferred to the object in the form of kinetic energy. However, what I don't understand is how ...
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### Why is $f = -\frac{du}{dx}$?

I am studying Newtonian Mechanics and I am familiar with single variable calculus. I came across the concept of conservative and non conservative forces and potential energy. Here is what I understand:...
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### Path of a particle acted by a force always perpendicular to velocity [duplicate]

What is the path of a particle if it is continuously acted upon by a force perpendicular to its velocity (given that acceleration magnitude is never equal to $v^2/r$)? Is it still a circle?
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### Astronauts being able to move “heavier” objects easily in space

I was watching this video where the astronauts demonstrate how an object that would weigh some large amount on Earth is nearly weightless in the microgravity experienced onboard the ISS. What I don't ...
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### Does horizontal motion decrease with the increase in gravity?

If a ball moves horizontally with a constant velocity in Earth compared to a ball moving with the same velocity but in a thicker gravitational field, will the ball move slower in the other plane ...
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### How is pulling on a rope attached to a cart due to electromagentic forces?

I have read in some textbooks (such as Griffiths' Electrodynamics) that ultimately there are only four forces underlying all physical phenomena: 1) Gravitational 2) Electromagnetic 3) + 4) Weak and ...
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### Does gravitational force do work onto an object being lifted?

If I am lifting an object upwards, is gravitational doing work onto the object? I am uncertain whether for this case, is it the force I exerted doing work onto the object or is it the gravitational ...
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### Why is it easier to push down a rope from the middle compared to the side?

Intuitively, if I push down on a rope at the middle, I know that it will sink down farther than if I were to press it at the sides. Below I drew a diagram of a person standing on a tightrope to give ...
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### How to optimally tighten a slackline with two ratchets

I recently got a slackline which has a ratchet (here's an example of the type I mean) for each end rather than a single ratchet. When I first heard of this type of setup, I'd thought it wouldn't help, ...
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### If someone is doing a weighted bulgarian squat and keeps the height of the weight static is their leg doing the same amount of work?

So imagine someone is doing this lifting exercise. However instead of the dumbbell being held at his chest, the lifter uses his arms to keep the height of the dumbbell static to the ground. So at the ...
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### In this world of pseudo forces what is real?

I was learning concept of pseudo force and encountered a problem which I found pretty interesting, I am told that the surface in contact of wedge and box having mass $m$ is frictionless and I am ...
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### What would be the consequences of action-reaction pair not being anti-parallel? [closed]

In the real world, action-reaction pair always make an angle of exactly at 180ᵒ. But what would happen if instead it was something like, say 179.9ᵒ. What would be the weird effects? I started off by ...
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### Literature recommendations for the relationship between fundamental physics and pure mathematics?

So, I have been reading up on the works by Kenneth Wilson, mainly his 3 statements that he concluded to be true about our universe. His first: 'There exists a hierarchy to our universe'. From this i ...
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### What is the mathematical description of a point torque (or point couple) singularity?

Suppose that a concentrated (point) force is exerted at the origin of a 3D dimensional space along the direction $\boldsymbol{e}$. Mathematically, this could be prescribed in terms of a delta Dirac ...
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### ${}$How do varying static point charges exert the same force on each other?

How can two different charges exert same force. We know the force is proportional to the product of the two charge which does make the force equal because it’s a product that it’s proportional to not ...
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### Reaction forces in ladder leaned on wall [closed]

I've got a ladder at some angle that is leaned on the wall. There is friction $T_1$ and $T_2$, and reaction forces $R_1$ and $R_2$. According to the rule that horizontal and vertical forces must equal ...