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 [tag:particle-physics] for decay channels due to forces and [tag:newtonian-mechanics] or one of the other subtopics of [tag:classical-mechanics] for the dynamics of classical systems.

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17 views

Why should forces add as vectors? [duplicate]

We are supposing in my mechanics course that forces add as vectors. But why, philosophically, should this be the case?
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How to calculate total force of 4 hydrolic power jacks?

The area of the 4 power jacks is known and also the pressure is measured and thus known using pressure gauges on pipe from the hydrolic power pack to the jacks. The jacks are identical and each of ...
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51 views

Spring force under gravity

Why do I have to use law of conservation of energy to solve problems regarding calculation of extension in spring length when a box attached to the lower end of the spring is released from rest (such ...
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2answers
63 views

Why can't I choose blocks attached with pulley B as a system?

Three blocks of masses m1, m2 and m3 are connected as shown in the figure. All the surfaces are frictionless and the string and pulleys are light. Find the acceleration of the block of mass m1. ...
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Estimate the force on your legs if you jump off a 2m high wall and land on your feet [on hold]

My final answer was 686.7N. I used F = ma, so let the mass be 70 because the average weight of a 15-year-old is near that. (the question was purposed for A-level students). 70kg x -9.81 m/s^-2 = 686....
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Method of resolution of forces numerical Question [on hold]

The resultant of two forces F1 and F2 is at right angles to F1. Determine the angle between the forces.
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26 views

How to determine the direction of components of force while solving the problems related to hinge force? [on hold]

There are two different directions of horizontal force in two different situations. Why?
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Calculate the time taken for a body to hit earth's surface [on hold]

Find the time taken for an iron cube of dimensions 0.1m × 0.1m × 0.1m, whose density is 7.85 g/cm³ to reach the earth's surface released from a height of 10m from earth's surface, provided gravity = 9....
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Calculating gravitational force with multiple planets [on hold]

I have a question regarding the following problem: Given the following system of planets (see image), calculate the total gravitational force acting on $m_3$. ($m_1 = 2 \cdot 10^{20}kg;$ $m_2 = 1 \...
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Measuring pressure or weight from an uneven weight distributed surface

I am new here so I hope I'm posting it at the correct place. I am having some troubles with some of my force sensors. My case is like this: I have a body which have a weight. However, the surface is ...
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Tension due to unequal forces on a massless spring [duplicate]

When a massless spring is pulled by 5N on both sides the tension in the spring is 5N (proved by considering COM at rest and breaking the spring into two springs of 2k each)...what if the forces ...
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What does strain actually mean?

A problem requires to find the stress in the portions AC and BC of the given figure when a given temperature change takes place. It is mentioned in the solution that total deformation of the ...
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Is the net force on atomic/molecular constituents of a solid body zero

So my question is this that suppose we consider a solid everyday object, say a spherical stone. Now, if I consider an atom or a molecule of the stone away from the center of the stone, then I can say ...
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Do flat plates result in less drag than concave surfaces? [duplicate]

Do flat plates (A) result in less drag than concave surfaces (B)? Intuitively, i think flat plates produces less drag than concave surface because the concave surface makes the fluid move backwards, ...
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The exact location of normal force and friction vectors [on hold]

I am struggling with a following question: "A cylinder of radius $r$ and height $h$ is standing on an inclined plane pitched at an angle $\theta$ to the ground. Given the coefficient of friction $\mu$ ...
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3answers
179 views

Total force on upper block in two block system

If a block $m$ is placed on another block $M$ and a force $F$ is applied on bolck $M$. Then how many forces are acting on block $m$.(Friction is non zero) The image is taken from this site. Is ...
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Why the sum of deformations in given figure is zero?

When a vertical block is kept between two fixed support and when the bottom support is removed, it has the possibility of facing a deformation downwards which was impeded by the upward reaction force ...
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How to find force from given torque and distance?

Let us assume that the rectangular board shown has a torque T at its centre of mass, due to which it is undergoing angular acceleration in clockwise direction. Let d be the distance from the centre of ...
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Can someone explain these circled points…?

Why is direction of friction in the direction of motion and here it is the platform that moves....the movement is not caused by friction so how is friction doing work? In the second one there is no ...
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${}$ A tug of war with different forces at each end of the rope [duplicate]

In tug of wars usually both the teams apply equal force on the rope resulting in the development of tension in the rope which is of the same magnitude as that of the applied force. But, now if one ...
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34 views

A tug of war with different forces at each end of the rope [closed]

If a man pulls a rope with a force of 150N towards him and the other end of the rope is pulled by a small girl with a force of 50N towards her. Assuming rope to be massless. Find tension in the string....
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1answer
33 views

From what point is the hydrostatic pressure formula not valid anymore?

The hydrostatic pressure formula (P=p.g.h) is used (eg) to calculate the pressure at the bottom of a container. Now this pressure is equal independent of the mass in it as long as the bottum surface ...
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1answer
73 views

Electron to electron interaction

I am interested to know if it would be possible to calculate the magnetic attraction between two electrons at zero space between their magnetic poles against electrostatic repulsion between them in ...
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Tension. Forces [duplicate]

Suppose I pull molecule A of a rope then it also pulls me back by newtons 3rd law. The force that I applied on the rope caused tension in the string , but then what is the effect of the force which ...
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1answer
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Newton's laws of motion tension

I am very much confused about tension. I have even Googled my doubts (Also used khan academy) to clear my doubts but even there explanation couldn't satisfy me. PLEASE SOLVE THIS QUERY:- what ...
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1answer
69 views

A doubt in a question of mechanics [closed]

Question: A mass of 2 kg is when kept on a ground,the ground yields steadily and the block goes down with an acceleration of 1 $m/s^2$. Find the reaction force on the block by the ground. I know ...
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1answer
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Newtons laws of motion. Tension force

What is the difference between tension and the force that we apply externally. Also when we apply force externally let's say on moleculeA ( connected to other molecules through springs) then by newton ...
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5answers
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Sum of gravitational force $W$ and contact force $N$ on a book at rest on table is not 0

There is a book on the table fixed rigidly to the earth. The book is at rest with respect to the earth. The acceleration of this book with respect to the earth is 0. The forces on this book are a) ...
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G Force on Saturated Sediment in a Lake - How to Calculate?

Can I calculate a g force on a saturated sediment in a body of water (a lake bed)? I have a hydraulic conductivity of the sediment and a vertical pore water flux. The pore water is moving upwards ...
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Force of attraction in capacitor [duplicate]

In a question, it was asked the force of attraction between the plates of a parallel plate capacitor. and it was solved as $$\frac{(1)(C)(V^2)}{2}=(F)(d)$$ $$F=\frac{(1)(C)(V^2)}{(2)(d)}$$ and I ...
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1answer
28 views

$\mu_k$ of surface from experimental vs theoretical acceleration [closed]

I have an air track at a slight angle with a glider. Final velocity is determined, and from that a is calculated, and from a, I have approximated g. I am trying to find $\mu_{k}$ between the track and ...
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3answers
97 views

Why are you doing no work when carrying a body through a horizontal distance?

Work done on an object is equal to $$FD\cos(\mathrm{angle}).$$ So, naturally, if you lift a book from the floor on top of the table you do work on it since you are applying a force through a distance....
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How do we predict the motion of this systems using Newton's laws of Motion?

This question should be seen as an argument for these Answers. I want you to read the answers to this following question before answering it. Violating Newtons First Law! Here Everybody is saying CM ...
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3answers
127 views

What does the equation ${\bf F} = m{\bf a}$ mean in this case?

So I have been studying about momentum and newton's second law. And I was wondering, if an object is traveling in space. If the object has a mass $m$ and a velocity ${\bf v}$ with an acceleration ${\...
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1answer
43 views

About working of tension force

From the past 3-4 days I have been continuously thinking how tension actually works on atomic level. I have even Googled it many times but I was not satisfied with the answers. Can anyone please help ...
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1answer
47 views

Length of Rope in Tug Of War Matter?

I had a question about Tug of War Game, Does the length of the rope really matter, whats the difference between a 50cm rope and a 5meter Rope in Force, Torque And Safety in Tug Of War.
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2answers
63 views

Technical question on definition of free fall

Free fall is any motion of a body where gravity is the only acceleration acting upon it. But, what if I threw an object from a certain altitude, and had two jetpacks put on it , one providing ...
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2answers
48 views

How is the angle same in friction force? [closed]

How is the angle $\theta$ of the plane and between the $mg$ (attraction due to gravity) and component of $mg$ is same? In the figure $\theta$ between the $mg$ and its component $$mg\cos\theta$$ is ...
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1answer
47 views

The pair potential different that $r^{-1}$

As I know, the potential between two particles of the form ~ $r^{-1}$ ($r$ is distance between particles) is special, because it solves the Poisson's equation in 3D. My question is: If I consider for ...
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5answers
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Can force be applied without accelerating?

When I push against a wall, I am applying force on the wall and the wall applies an equal force against mine therefore the wall doesn't move and neither does my hand. But isn't acceleration required ...
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1answer
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Finding displacement by integrating forces that vary with velocity

I have a body that is being affected by forces, some of which are invariant ($F_i$) and some of which vary with velocity ($F_v(v)$). Given that $F=ma$ (where $F=F_i+F_v(v)$), how do I integrate this ...
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How to calculate the velocity and radius of curvature of a charged particle in a perpendicular magnetic and parallel electric field?

If I have a charged particle come from a point velocity V1 where there is a uniform electric field parallel to the motion of the particle which accelerates it and a magnetic field perpendicular to ...
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20 views

What is the adverse pressure gradient?

What is the adverse pressure gradient? Is the pressure gradient increasing along the direction of motion of the fluid a adverse pressure gradient? Does it cause the wing to stall?
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1answer
37 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 ...
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Reversed effective force in D'Alembert's Principle [duplicate]

In D'Alembert's Principle,what is reversed effective forces and how to determine it's direction?
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Physics of Athleticism for Dunks

I was curious of the athleticism I'd need to dunk a standard rim at $10$ ft above the ground. Using an online calculator, given that I am $5$ feet $6$ inches tall with a standing reach of $7$ feet $1$ ...
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3answers
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Tension in a string attached to different masses

Does tension in a string remain same even if masses attached to it are of different weights? I have provided a diagram, according to me the tension in string should be different as masses hanging ...
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1answer
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Forces acting on an object about to hit the ground

I have a simple question, If I have a spanner or (any object) and I drop it. As it's just about to make contact with the ground what would the main forces acting on it be?
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2answers
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Why is the force not shown when the body is split into components?

In the given figure, for ease of determining the reactions, the body has been split. The component figures shows internal forces but not the load P. How is this possible ? (Though the figure does not ...
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How to determine the minimum force in these questions?

Take a look at this example The author mentioned that the shortest path when the angle is 90 which is clearly obvious. Now take a look at the following problem from the same book The author has ...