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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 problem related to adhesive and bonding

I have two PCBs (printed circuit board), and they are glued by adhesives, as show in the pictures. And the location of the adhesives are indicated on the picture (please notice that NO adhesive is ...
Delay No More's user avatar
6 votes
0 answers
448 views

Minimum velocity required to "skip" a spacecraft across the atmosphere?

When, hopefully, Virgin Galactic spacecraft start regular operations in a few years, they will be simply travelling upwards, then achieving weightlessness for a short while, followed by a return ...
user avatar
5 votes
0 answers
107 views

How to calculate the required force to from lever to pushrod in order to close calliper in a hydraulic braking system?

How to calculate the required force to from lever to pushrod in order to close calliper in a hydraulic braking system? Through test and data i have determined the average force on a bicycle lever is ...
user avatar
5 votes
3 answers
2k views

Reaction force exerted by pulley's support

Consider an in-extensible string passing over an ideal pulley connected to a block of mass $m$ as shown: The ends are pulled with a force $F$ Am I correct in saying that the block will experience a ...
newbie105's user avatar
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5 votes
0 answers
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3-force in General Relativity

Let's consider the definition of 3-force in different theories: Newtonian mechanics In Newtonian mechanics, we can define the force as a cause of changing momentum $p=m\vec{v}$ with time. According ...
Sergio's user avatar
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5 votes
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Calculating forces via Feynman diagrams?

How would one go about calculating forces that test objects feel using Feynman diagram methods? For example, say we have a massive object in GR so that the metric takes on the standard Schwarzschild ...
user26866's user avatar
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5 votes
1 answer
456 views

Semiflexible discrete polymer chain

Suppose we have a 2D polymer model described by a set of 2D vectors {$\mathbf{t}_i$} ($i=1,2,\dots N$) of length $a$. The energy of the polymer is given by: $$ \mathcal{H}~=~-k\sum^N_{i=1}\mathbf{t}...
molkee's user avatar
  • 185
5 votes
1 answer
580 views

Is the Weak Force really a force?

My definition/understanding of a force still carries largely over from classical physics which is something that tends to change the motion of an object (a push, pull). Gravity and electromagnetism ...
john hon's user avatar
  • 161
4 votes
2 answers
754 views

Why is $mg$ split into components instead of the tension in vertical uniform circular motion?

I am a beginner physics student. I am trying to prove that the magnitude of the tension varies sinusoidally as an object P travels around the circle or something of that sort. Thus, I am evaluating ...
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4 votes
2 answers
440 views

Being Frictionless, surface of contact

I frequently hear references to a smooth surface, or frictionless pulley. Can being frictionless be obtained if only one of the 2 surfaces has 0 coefficient of friction? Or is it for the contact of ...
user avatar
4 votes
1 answer
126 views

What does it mean for a force to 'produce' virtual displacement?

Book: Variational Principles of Mechanics by Lanczos, 1st edition, 1949. Statement (page 80): "Two systems of forces which produce the same virtual displacements are dynamically equivalent."...
Mandar's user avatar
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4 votes
3 answers
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What are pre-collisions and post-collisions in forces and momentum?

What are pre-collision and post-collision exactly? I assume it is before collision and after collision. I can not find an answer on google.
Jon Wick's user avatar
  • 107
4 votes
0 answers
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Gravitational force for a binary of point particles with GR term

i'm trying to simulate the two body problem with 2 equal masses and I want to account for general relativistic effects. I know that the difference in the gravitational force would be an additional ...
6548873432486's user avatar
4 votes
0 answers
778 views

Lorentz force on superconductor vortices

I am reading a paper on superconductivity and in it it says that the vortices are subject to a Lorentz force given by $$\vec{F}_L=\frac{\Phi_0\vec{I} \times \vec{H}}{cH}$$ Here $\vec{F}_L$ is the ...
Rather's user avatar
  • 41
3 votes
0 answers
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Discrepancy between theory and real life: spool and mass system connected via pulley

I was given this problem in physics class. My teacher said that they reached the ground at the same time, but when I tested it out (video), I got drastically different results. I showed the professor ...
Christian Vela's user avatar
3 votes
0 answers
193 views

What weight does a scale show when you throw an object onto it?

Imagine you have a bucket (cross-sectional area $A$) on top of a scale. Into the bucket you begin to pour sand (density $\rho$) with a mass flow rate of $\dot{m}$. The total weight of the sand in the ...
S. Green's user avatar
3 votes
4 answers
85 views

Is the Lorentz force applied to bulk objects?

Assume that a bulk uniformly charged ($+Q$) nonconductive sphere is set in motion inside a uniform magnetic field. Is it correct to claim that the trajectory of the bulk sphere inside the magnetic ...
Mohammad Javanshiry's user avatar
3 votes
0 answers
140 views

Are the force frequencies the same in the discrete and continuous case?

Let's say I have an ideal gas of particles and the strike zone of area $\sigma=\pi d^2$ of a molecule of the molecule is what is the sub system considered. The end of the face of the cylinder is the ...
More Anonymous's user avatar
3 votes
0 answers
87 views

Differential geometry and the $P \vec A= \vec F$ equation?

How does one write $$\vec F = P \vec A$$ (where $\vec F$ is the force. $P$ is the pressure and $\vec A$ is the area) in the language of differential forms? I'm confused cause $\vec F$ is a one form ...
More Anonymous's user avatar
3 votes
0 answers
71 views

Struggling to prove Newton's Law of Gravitation starting from smaller bodies

I have seen at least four different posts in this website in which the OP asks for a proof of Newton's Law of Gravitation (often without stating from which axioms the proof should start) all of which ...
Sam's user avatar
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3 votes
0 answers
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Where does Okun's formula come from?

The formula is $(16)$ in Lev B. Okun's paper "The Concept of Mass". It gives the force acting on a light body by a heavy spherically symmetric mass according to general relativity. ...
Elio Fabri's user avatar
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3 votes
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Force on a ring due to EM induction

Question:- Two circular coils of radii '$a$' , having resistance per unit length $\lambda$, are moving with uniform speed '$v$' along x-axis as shown, in a uniform magnetic field $\vec B=-B_0\hat k$. ...
Ankan G.'s user avatar
3 votes
0 answers
124 views

How did the Lagrangian and Hamiltonian theories of motion inspire the idea that forces should be treated as one-forms instead of vectors?

On page-5 of this paper1 by E. Minguzzi titled "A geometrical introduction to screw theory", he writes: Who adopts this point of view argues that it should also be adopted for forces in ...
Babu's user avatar
  • 7,960
3 votes
2 answers
102 views

How do we account for the non-net accelerations for forces in static systems?

I've googled the heck out this (as a non-physicist) and found a ton of similar questions answered but did not find anything that made the light bulb go on. I don't think I'm a crank, so here it goes. ...
Zduff's user avatar
  • 131
3 votes
0 answers
444 views

How does pulling backwards on the pedals cause the bike to move backwards?

I saw this video by George Hart recently: https://www.simonsfoundation.org/2014/03/20/mathematical-impressions-the-bicycle-pulling-puzzle/ Hart attached a string to the pedal while it was on the ...
rcplusplus's user avatar
3 votes
2 answers
315 views

Can we have pressure with zero net force on a 2d plane?

From Wikipedia: Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Suppose we apply 2 equal and opposite forces on a 2d plane ...
Pranav K's user avatar
  • 540
3 votes
0 answers
132 views

In fluid mechanics, why are the forces on the fluid the same as the forces on the control volume?

From the momentum equation of fluid mechanics: $${\frac{\partial}{\partial t} \int_{V_f(t)} \rho \vec{v} \text{d}\text{V}} = \int_{\sum_f(t)} \vec{\bar{\bar{\tau}}} \cdot \vec{n} \text{d}\sigma + \...
Patricia GC's user avatar
3 votes
0 answers
22 views

Will the beaker be acted upon by the force in the direction of the green arrow?

The black circle is the top view of the beaker. In the gravity field, the beaker is vertical down along the beaker axis. The beaker is still. The water in the beaker rotates at a uniform angular speed ...
enbin's user avatar
  • 2,036
3 votes
2 answers
902 views

Table on inclined plane - normal force

So, I'm struggling to understand how the normal force works in case of the inclined plane. It's obvious for me what happens if the body is, for instance, a block or a cylinder, however, I can't got ...
A. J. Bałaziński's user avatar
3 votes
4 answers
208 views

Applying an external force from inside a ball

I know that to accelerate an object we have to apply an EXTERNAL unbalanced force. I thought about the following situation. I am inside a large transparent ball. I want the ball to move forward. I ...
Ashok Sharma's user avatar
3 votes
1 answer
858 views

Force balance for belt-pulley-mass model (2nd order response system)

I am trying to model a mass being driven by a motor (Angular acceleration $\dot{\omega}$ and shaft-polar modulus $J$) with belts and pulleys. This is then being compared to numerical simulations. I ...
dearN's user avatar
  • 603
3 votes
0 answers
137 views

What does Newton's third law actually look like with a finite speed of causality?

Newton's third law of motion states (as quoted on wikipedia): When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction ...
A. Ok's user avatar
  • 653
3 votes
0 answers
201 views

Newtons law of gravity from Wilson loops?

Wilson Loops in Quantum field theory $W_\gamma = trPexp(\int_0^1 dt \dot\gamma_\mu A^\mu)$ for curve $\gamma(t)$ and Connection $A^\mu$ are used to define an effective force law of a theory in a ...
kryomaxim's user avatar
  • 3,458
3 votes
1 answer
92 views

Could a hydrophobic surface increase a liquid's resistance to compression/displacement?

Imagine a quantity of an aqueous (yet slightly viscous) solution is resting on a hydrophobic surface with a contact angle around 100°. A downward force is then applied as a (repellant) surface is ...
mxwln's user avatar
  • 31
3 votes
0 answers
94 views

Time evolution of symmetrical mechanical systems

I asked this previously in an earlier question, although admittedly my question was hard to find in the slew of info I provided there, so hopefully this will clarify things. Suppose there's a typical $...
DumpsterDoofus's user avatar
3 votes
0 answers
309 views

How do we derive force/acceleration vectors from Einstein's field equations?

I'm new here and I don't have any formal experience in physics beyond A-level. I've been exploring an idea for a space sim game someone else is developing in which propulsion of a spacecraft is ...
Tagc's user avatar
  • 139
3 votes
1 answer
195 views

At what $ω$ would the dust particles fly off the tilted rotating disc?

I've been struggling with question below: "A metal disc of radius R can rotate about the vertical axis passing through its centre. The top surface of the disc is uniformly covered with dust ...
PinkAura's user avatar
  • 349
3 votes
1 answer
598 views

Hanging clothes on a windy day

Hanging clothes on a windy day can be really challenging, especially if you don't have any clips lying around. Today I was hanging the clothes out in the drying area of my hostel. But soon, it turned ...
AlphaLife's user avatar
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3 votes
1 answer
182 views

Is there something wrong in my book's derivation of work done on charge?

For finding potential at a point due to a +ve charge $(q)$, we find work done to move a unit +ve charge $(q_o)$ from infinity to that point in the presence of +ve charge $(q)$ Since both charges ...
stack exchange's user avatar
3 votes
1 answer
212 views

What does it mean that Bruno can hit $6\,\rm{kN}$?

Is it the momentum? But momentum is $\rm{Ns}$, not $\rm{N}$. http://www.skepticforum.com/viewtopic.php?f=32&t=14624 I'm not sure that 3,430 N is necessarily beyond human capability. Boxer ...
user4951's user avatar
  • 601
3 votes
1 answer
465 views

What will be the direction of the force required on the ball to move the ball up the stairs?

Is this diagram correct? The point of force A is at the farthest distance from the fixed centre O ,so the moment arm CD is greater and therefore,maximum torque would be produced.Is my concept correct?...
user3244786's user avatar
2 votes
0 answers
22 views

What are the conditions according to which the levitation force between a magnet and a superconducting material tends to zero?

According to this article, for a disk-like superconductor and a magnet, if the radius of the superconductor tends to zero or the radius of the magnet tends to infinity, it seems that the levitation ...
Mohammad Javanshiry's user avatar
2 votes
1 answer
160 views

Does the charge distribution of two uniformly charged conducting spheres change as we bring them near each other?

Assume that we have positively charged two solid conducting spheres of the same radius and material. It is evident that the surface charge is uniform on them to eliminate the internal electric field ...
Mohammad Javanshiry's user avatar
2 votes
1 answer
165 views

Are there any relativistic corrections to electrostatic attraction between two charges moving close to the speed of light?

If two opposite charges are moving at a velocity of $0.9c$ relative to a laboratory, but are at rest relative to each other (say the charges are moving in parallel), will there be any relativistic ...
Robert's user avatar
  • 79
2 votes
1 answer
136 views

On the infinite range of the electromagnetic force

I am curious as to whether there is a fundamental reason why weak and strong nuclear forces have such a short range whereas gravity and the electromagnetic force seem to have infinite range. Since ...
Ambica Govind's user avatar
2 votes
0 answers
941 views

Proof of principle of transmissibility of force

The principle of transmissibility states The point of application of a force to a rigid body can be moved anywhere along its line of action without changing the external reaction forces. My question ...
user716190's user avatar
2 votes
2 answers
102 views

Surface tension of a fluid

I understand that there is an imbalance of forces between molecules that lie on the surface of a fluid compared to those that lie within. This results in the surface area is minimised. However, I can'...
James Chadwick's user avatar
2 votes
0 answers
71 views

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 ...
Tom's user avatar
  • 1,218
2 votes
0 answers
58 views

Microscopic description of drag

It is well known that a fluid opposes the motion of a moving object and we can represent this resistance in motion with a force, which we call it drag. Different fluids exert different drag forces ...
Antonios Sarikas's user avatar
2 votes
0 answers
82 views

Untwisting Strands of a Rope

Statement:: Topoisomerases help in relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix (Topoisomerases are enzymes that participate in the over ...
Aurelius's user avatar
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