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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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 ...
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2answers
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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 ...
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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-...
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1answer
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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 ...
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1answer
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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 ...
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2answers
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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 ...
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0answers
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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 ...
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1answer
51 views

Potential energy and force [duplicate]

Why force is negative gradient of potential energy? Why negative sign is involved in this definition?
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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 ...
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1answer
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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.
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3answers
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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 ...
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2answers
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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
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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. ...
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6answers
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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 $F=ma$?
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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 ...
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3answers
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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 ...
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0answers
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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 ...
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1answer
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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 ...
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3answers
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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.
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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 ...
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1answer
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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 ...
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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? ...
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3answers
174 views

Problem with gravity

Sorry if this question is dumb, but I don't seem to have a grasp on it. Suppose you are on a rock in space, with no external forces acting. The rock attracts you with a force given by $$F=G\frac{...
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3answers
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Is pseudo force just an ad hoc number to explain motion in non-inertial frames?

Consider an observer in a non-inertial frame $S$ who observes a particle's motion with a relative acceleration $\vec a_s$ and further calculates (or was told by his fellow observer in an inertial ...
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0answers
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Dividing torque of one axle to three in varying proportions [closed]

I want to power a small mechanical monstrosity, which performs three tasks that require three separate axles. For the powering, there's a hand-operated crankshaft connected to the primary axle that ...
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2answers
90 views

Time taken for a body to crash into the sun [closed]

A small body starts from rest towards the Sun from the position of Earth, find the total time it takes for the body to crash into the Sun (assume Sun is a point object and no other forces act on the ...
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4answers
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Parallelogram law of vectors

[This is a very silly question. Will be a great help if someone could answer this question] How is this law proven? I am not asking about the proof itself rather asking about the preliminary ...
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If the rope is 1.2m long, at what speed must the bucket move so the tension is 0 at the top of the rotation? [closed]

A bucket of water connected to a rope is spun in a vertical circle. If the rope is 1.2m long, at what speed must the bucket move so the tension is 0 at the top of the rotation?
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5answers
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Why do we multiply $\cos θ$ in the formula for work?

I know that the formula for work, $W = FS\cos\theta$, where $F$ is the applied force, $S$ is the displacement of the object and $\theta$ is the angle between the applied force and the displacement of ...
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2answers
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Will the position of the Centre of Mass remain unchanged?

I know that internal forces won't accelerate the centre of mass of system, but assuming there are three objects in a system and two of them move due to the internal force exerted by one and the ...
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1answer
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Tension at any point of a hanging rope

A common question to those initial practitioners of classical mechanics it to find the tension of a rope hanging between two trees, at the end and the middle. Below a graphical description of the ...
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1answer
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Understanding the balance of forces

An "object" that has the shape of an inclined plane has a slot that carries a roller bearing attached to an extension spring. When a force F1 is applied to the left, the object moves and the ...
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5answers
63 views

Please explain the walking mechanism

When a person walks, he exerts a force on the road, lets say $F$, and the road exerts a force on the legs (friction), lets say $f$. Newton's third law says that $F = f$, so why is $f - F = ma$? Where ...
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1answer
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What are the forces acting on the block?

Imagine holding a piece of block with two fingers. The forces acting on it are $mg$ downwards, contact force $F$, and frictional force $f$. The block is at equilibrium under the action of this forces....
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4answers
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'Simple' capacitor problem

I posted this question because I have a problem in grasping the connection between force on a charge and voltage potential equilibrium. So the problem is the following: we have a charged capacitor ...
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1answer
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Confusion with force and time

It is said that force is an interaction that causes an object to accelerate. It is measured in newtons. $1$ N of force causes an object with a mass of $1$ kg to accelerate at $1$ m/s². Now let's ...
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How high can sand pile up?

I read a question about sand. In one answer, an hourglass was mentioned. Suppose you have enough fine, dry sand. If you create a pile of sand by letting a beam of sand fall down on the land (like in ...
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3answers
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Conceptual doubts about Force and Gravity [closed]

First Question: Force applied for a span of time. Let's say a force $F$ is applied on an object of mass $M$. So, the acceleration of that object in the direction of $F$, would be, $a = F/M$. Now, if ...
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0answers
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How to determine the force exerted by a fluid stream on a plate [closed]

This is related to Problem 1 in Chapter 2 of "Rocket Propulsion Elements, 9th Edition": A jet of fluid hits a stationary flat plate in the manner shown. (a) If there is 50 kg of fluid ...
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3answers
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The unit of Torque [duplicate]

Whenever we define a physical quantity, we know what 1 unit of that quantity tells us. For example, when we say 5 Pa, we're saying 5 N force acts perpendicularly on every unit area of the material but ...
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1answer
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Stair machine Vs stairs. which is harder?

I had a big argument at the pub about the stair machine being easier than actual stairs, and all the people there disagreed, saying that the only difference is air resistance? Are they kidding? My ...
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1answer
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A runner against the wind

We have a runner that is running against the wind. The wind speed is $10 m/s$. The runner is using the same power when he is running against the wind and also when there is no wind, but we know, that ...
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2answers
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Is the value of the work done by the forces acting on a rigid body frame dependent?

I was going through the definition of "Work of Forces Acting on a Rigid Body" in Wikipedia . Here they have mentioned that work done can be calculated by taking any reference point on the ...
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1answer
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External force and centre of mass [closed]

I’ve read that linear momentum of a system will be constant when there is no external force on the system. Thus, the velocity of the centre of mass will be the same. Thus, this means that the position ...
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0answers
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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 ...
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1answer
53 views

Force between two charged shell [duplicate]

Suppose we have two charged shells with a distance between the two centers that they cannot be considered as point-like charges in the mutual interaction, for example three times the radius. Can we ...
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1answer
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Impulsive forces

A force $F$ acting from time $t_1$ to $t_2$ on an object causes a change in its momentum $p$, as in $$\int_{t_1}^{t_2}Fdt=p(t_2)-p(t_1)$$ If this expression is now differentiated with respect to time, ...
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1answer
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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 ...
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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,...
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4answers
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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 ...

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