# 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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1answer
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### How to evaluate acceleration for a body attached with an extensible string?

I got a problem where they first said the body is attached with an inextensible string. Then it asked to find out the tension and acceleration. At the end they asked what change in your answer will ...
2answers
10 views

### Working out max stress/moment on a gymnastic ring

I am trying to work out what is the max force/moment my gymnastic ring experiences when I hang from it. The ring has an overall diameter of 200 mm and a cross-section diameter of 25 mm. My weight is ...
0answers
23 views

### Could the ITER central solenoid lift an aircraft carrier 2 m into the air?

This claim is made in many places around the internet, presumably repeated from an ITER press release. But are there caveats? Does the aircraft carrier need to be in water (so only the no-longer-...
1answer
34 views

### Why work done by tension (like string force) is always zero?

A fixed disc free to rotate about its center (a flywheel) has a string wrapped around it, with a block attached to it. As the block falls, The tension in the string makes the disc rotate. Now, when ...
1answer
31 views

### Feynman Diagram Mediated by Positive Pion? [closed]

I don't think it is Strong Nuclear as it would be a negative pion, neither do I think it is electromagnetic as there are no electrons. Weak Force I believe would need a neutrino, so is it ...
2answers
47 views

### What is the pressure that dark energy exerts on stars and planets while increasing the distance between them?

What is the pressure that dark energy exerts on stars and planets while increasing the distance between them? I can understand that the pressure should be at a volume scales lower than molecules ...
0answers
18 views

### Morison Equation - Value of K not working

Need a hand with the Morison Equation with $k$ giving me a headache. I'm following a video online trying to calculate the force on a structure I am designing for work. I try to follow videos using ...
1answer
51 views

### Potential energy and force [duplicate]

Why force is negative gradient of potential energy? Why negative sign is involved in this definition?
3answers
67 views

### Example that seems to violate conservation of angular momentum

Mass m is rotating on a horizontal friction-less plane around a tiny hole. A massless string is connected to mass m and the other end of it is slowly pulled. Taking the center as our origin we see ...
1answer
30 views

### Formula for calculating sliding friction

What is the formula for calculating frictional force of a sliding body? I have already tried $F=UR$ but it is not working.
3answers
39 views

### Action-reaction force diagrams

I have an issue with the force diagram examples of reaction forces. It doesn't define where the "action"/applied force is coming from. If we were to draw free body diagrams, then for object ...
2answers
37 views

### Why do I feel centrifugal force If I move with constant speed on a turn?

Title sums it up pretty much, I'm studying for my physics exam right now and I just can't wrap my head around this
0answers
32 views

### James Thomson's hypothetical ice engine

I do not have a background in Thermodynamics. Imagine a piston/cylinder arrangement (like the one in a steam engine) in which the space below the piston is filled with water. This is cooled to 0°C. ...
6answers
167 views

### Why $F=ma$? Why not $F=mvs$ or something else?

Newton defined rate of transfer of momentum from one particle to another as force. Can we predict motion using F=mvs or something similiar instead of $F=ma$?
2answers
880 views

### Since photons are said to be the force carrier of electromagnetic force, does it mean that photons get transferred from golf club to golf ball?

Just like it says in the question title. I have heard that photons are force carriers of electromagnetism. Is it not true, that when a golf club imparts force on to a golf ball, then the fundamental ...
3answers
62 views

### Problem with Action-Reaction pairs and gravity [duplicate]

There are lot of question on this site similar to this, but they give contradicting opinions. When standing on earth, my gravitational pull to the earth and earth's gravitational pull towards me ...
0answers
40 views

### Dynamics of a double atwood machine [closed]

I am stuck with this question and need help In the figure, In the figure $$m_3>m_2>m_1$$ $T$ is the tension in the lower strings $T_1$ is the tension in the upper strings $a_2$ is the ...
1answer
52 views

### What minimum force would you need to apply in order to do work against gravity without accelerating an object? [closed]

In this example, the object is placed on a frictionless surface. After letting go, the object travels back and forth on a U-shaped tack. Without a mass or angle to the incline, how am I supposed to ...
3answers
84 views

### Is EMF a force? [duplicate]

I had a confusion. EMF stands for electromotive force. Is it a force? I have a short question and I can't elaborate more but this site is not allowing me to post so I am writing.
0answers
39 views

### Finding the point between two masses where a third mass would experience equal pull from the other two masses [closed]

Here is the question: The Earth and Jupiter are 698.58 million km apart. The mass of the Earth is $5.972 \cdot 10^{24}\mathrm{kg}$ and the mass of Jupiter is $1.898 \cdot10^{27}\mathrm{kg}$. Find ...
1answer
41 views

### Friction problem when object is constrained

A $60 \;\text{N}$ force is acting on an object of mass $10 \;\text{kg}$ which is placed against a wall touching it. What is the normal force $N$ applied by the wall? My method: Since the object ...
2answers
49 views

### How much force would be needed to do a pushdown? (moving the Earth downwards when you do a pushup) [closed]

This is kind of hypothetical, I know this isn't humanly possible, but assuming the earth weighs about 5.972 × 10^24 kg how much force would it take to move the Earth downwards while doing a pushup? ...
3answers
174 views

1answer
76 views

### Why do ants feel more difficult to climb when height increases?

I have noticed that whenever an ant (carrying something) climbs a vertical wall, it easily climbs the lower part of the wall but as the height increases, the ant finds it difficult to climb and at ...
1answer
35 views

### The behaviour of acceleration of a ball in motion

I have a few doubts on how the acceleration of a ball works when we throw it up in the air, In my mind, I could imagine it in some different "real world" cases, So I am listing them all down,...
4answers
48 views

### Law of conservation of momentum and force

It is said that internal forces do not change the state of rest to motion only external forces can change it. But in case of a gun, a gun applies force internally to the bullet inside it and the ...