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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Do internal forces of an atom lead to motion? [closed]
Do internal forces of an atom lead it to move, or can an atom only move when an external force is applied to it? For example, if we had a perfect vacuum with the exception of one arbitrary atom, would ...
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Why does bunched up aluminum foil become so extremely hard to compress?
I noticed that whenever I bunch up aluminum foil (into a ball), it becomes extremely hard to compress.
If I use another piece of the same amount of aluminum foil, and keep folding it in, I arrive at ...
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Forces acting in a system (internal/external)
Consider a rocket taking off. It can be thought of two objects, a body and the ejected fuel. At some point in time (instantaneously) the mass of the body is $m$ and the mass of the fuel ejected is $M$,...
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Questions about space elevators
I'm slightly confused about where exactly the forces involved in a space elevator are being applied, and my lack of a degree in physics makes it difficult for me to understand the sources that google ...
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How does this art work balance itself?
The artist Ariel Uzal* is showing a piece at UCLA that consists of a platform that is being moved on a horizontal plane by a rotating motor with an attached arm. The motor is moving at a constant ...
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How long would it take for a flashlight in space to reach an speed of 1000 metres per second? [closed]
I started from the question of a solar sail https://en.wikipedia.org/wiki/Solar_sail then imagined a flashlight sitting in space with no forces acting upon it, if it was then switched on, the photons ...
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The equilibrium point of a spring pendulum [closed]
I don't know where the equilibrium point is if the spring vibrates with a maximum amplitude of A when I pull out my hand right away in that situation. I'm confused whether the equilibrium point is ...
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How will the joint move because of expansion of strut? [closed]
When strut D-A stretches because of axial force, how will the joint in A move if we neglect other deformations?
Will it follow a circular arc because AB doesn't change length?
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Conservation of energy when 2 unequal forces are acting on a body [closed]
How will energy be conserved if two unequal and opposite forces (force1 &force2) are acting on a body, and the net force led the body to be displaced? What is the work done by force1 and force2 (...
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Can Newton’s system of particles be used to solve this constrained motion? How? [closed]
Thanks the picture from quora.
No friction on pulley.
I would like to know how to solve detailly with the Cartesian coordinate and vectors clearly.
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Shouldn't Electric Potential energy be $U=2kQq/r$?
Let's take 2 charges $Q$ and $q$ a meter apart. Say you want them to collide. You'll have to apply force $F$ on charge $q$ (which I know is changing with distance). I know we integrate this force and ...
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Why we take $k=1$ in $F=ma$? [duplicate]
I know that $F$ is directly proportional to mass and acceleration but why in formula we take $k=1$ not other constant?
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How Work Done is Calculated for Changing Direction?
I know work done is equal to product of force, displacement and cosine of angle between them. But that formula works only when we assume that the force is constant during displacement and it acts so ...
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Que on STRESS (MECHANICAL PROPERTIES OF SOLIDS)
See, it's a simple question.What exactly is stress? Is it the restoring force applied by the body in reaction to deformation force or is it the deformation force itself? I had this doubt because in ...
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Why should the tension be constant throughout if there is external force? [closed]
I came across a question from Pathfinder for Olympiad. The question was:
A frictionless non-conducting inextensible thread of length l wears three beads of positive charges q1 , q2 and q3. The ends of ...
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On inclined plane, a truck pulling up a cart attached with rope [closed]
On inclined plane, a truck pulling up a cart attached with rope,
there's no friction between the cart and plane but there is between
truck and plane. The truck climbs an uphill road at a given ...
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If two opposing equal forces act on an object, how does one calculate the energy exerted? [duplicate]
If energy exerted is a function of distance and force, the object would not move in this case. But would energy not still be exerted?
Simplified the example for sake of clarity; but specifically ...
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I am Not understanding how the Reaction force is calculated this way. Could you please explain? [closed]
In the following question, I am not sure why the reaction force of the pully can be calculated this way.I was expecting something like sqrt(2) T1 as an answer. I would very much appreciate it if you ...
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How to use Impulse relation? [closed]
Consider the following question from Kleppner and Kolenkow (4.10-second edition)
A freight car of mass M contains a mass of sand m. At t=0 a constant
horizontal force F is applied in the direction of ...
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I want to know the answer not sure if mine is correct [closed]
[][1 I want to know the answer not sure if mine is right I got 240N for the driving force 600000 joules for work and 800 for power
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Weighting unbalanced object
Hopefully my question is not out of order in this site.
I am trying to weigh an object that is too wide/long for my weight scale. If just put it on top of it it tips over.
So my solution is to place ...
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What dot product means when it's 0?
The following image taken from one of the books:
As it says, it moves to the dotted line which means box will move to the $x$ as well as $y$ direction.
In the same book, there's a vector product ...
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What's a classroom demonstration that an object with balanced forces can move at a constant velocity?
It is quite easy to demonstrate that an object at rest that has balanced forces doesn't move. All the Internet examples of things that have balanced forced moving are large scale objects - cars and ...
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Plank overhanging off a building — where does the normal force go?
Suppose there is a (uniform rectangular) plank of mass $m$ and total length $L$ that is on top of a building with some piece overhanging or jutting out past the building. Assume it isn't past the ...
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Clarification on Newton's 3rd Law
I was looking for some clarifications on Newton's 3rd Law.
I've heard that a book resting on the surface of a table is not an example of Newton's 3rd law. The Earth's gravity pulls down on the book ...
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How tensions of $y$ axis are different, but overall tension still the same?
Let's say rope is at equilibrium and both ends are attached to something(boxes). We put a finger on it and let go. So it starts accelerating upwards.
Let's consider just a tiny, tiny piece of the ...
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The force experienced on a charge, using macroscopic quantities
Zangwill says (Zangwill, Modern Electrodynamics, 2012 edition, page 40, undersection 2.3.1, "Lorentz Averaging")
...An example is the force on the charge density $\rho$ and current
density $...
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Forces on the Palm Tree in Baahubali 2
I'm working on a project for physics class where we are asked to analyze the physics of a movie. I chose this scene (2:00) from the movie Baahubali 2. I was wondering if the palm tree works like a ...
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Ratio between electric and magnetic forces
Suppose I have two beams of electrons moving at speed $v$ separated by a distance $d$. I can work out magnetic and electric forces between them...
For the magnetic force, we treat the two beams wires ...
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Pushing off another object — why does the other object do work on you without expending any energy?
Suppose you are in space (or on a frictionless surface) next to another object of the same mass $m$ as you. Take the reference frame of the center of mass of you and the object (so there is zero ...
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Influence of slide mass to recoil of a pistol
All other things being equal, how does the mass of a pistol's slide effect the recoil imparted to the shooter?
Background: firearm enthusiasts often assert that the larger the "reciprocating mass&...
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Are the definitions of force and acceleration circular? [duplicate]
Force is defined by acceleration , and acceleration requires the determination of" inertial frames".
But an inertial frames also requires the knowledge of forces which requires measuring ...
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Is $F= ma$ applicable in only those cases where mass of the body remains constant? [duplicate]
Is it correct to say that $F= ma$ is valid for cases where mass remains constant? Suppose a snow ball is rolling down a hill and gaining mass continously so can't we say net force on snow ball at any ...
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Time lag for generation of electrostatic force
Suppose we make a certain point in space charged. Say we impart some negative charge, such that electrostatic condition is maintained.
Then, after the point gets charged will the electric field due to ...
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Force not applied on center of mass
I have a question about rigid body motion when a force acts on off-center of mass.
I read the answer to the post force applied not on the center of mass but I'm still confused.
I understood that ...
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If two ends of a rope in equilibrium are pulled with forces of equal magnitude and opposite direction, why is the tension in the rope zero?
If the pulling fores are of equal magnitude and in opposite direction. Explain why the tension in the rope is zero.
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How can I calculate the tension at an angle in string at here by considering the vertical component of tension? [closed]
The answer said if vertical component of the tension was considered, it will be 775N. Without considering it, i got 1154N.
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Should tensile or compressive force be applied?
When a railway is laid in a cold environment, should tensile or compressive force be applied? How does this work? I think the answer should be tensile. The railways expand while heated so applying ...
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Forces acting inside conductor in an electric field
In the book on electrostatics and magnetism by Purcell. In the third chapter he mentions about conductors in the electrostatic field.
In the static situation there is no further motion of charge. You ...
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Why does moment/torque equal to force multiplied by distance?
moment is equal to force x distance but why is is it so. why is it so that greater the distance less the effort needed? i tried understanding it mathematically but it just went over my head. if any ...
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Does it take less pulling force to unplug cable if the "length" increases?
Why/Does it take less force to unplug the cable if you pull it at a bigger lengths?
I've tried many times and it seems so.
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Analysis of simple pulley system
I have some questions about the motion of the simple pulley system illustrated in the book Machinae novae. Are the following conclusion about the system correct?
Since the length of the rope is ...
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Doubt in Hooke's Law. Coordinate system
Hello! I have a question about Hooke's Law.
In the first image, the force experienced by the spring when it is stretched a length $x$ from its equilibrium point $x=0$ is given by $F(x)=-kx$.
In Hooke'...
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Simple stresses and strains
Why nature of stress in a state of stress at a ponit is as same as applied force even the stree is opposite to the applied load
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Mathematically proving that it is always possible for a rigid body to maintain its rigidity
Consider a rigid body $\mathcal{B}$ modeled by a system of $n$ point masses $B_1,B_2,\dots, B_n$ constrained to keep constant distance from each other. I wonder how it is possible to mathematically ...
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How is a cupboard stable?
Take a cupboard or just a large wooden box. When pushed it a point above its center of mass, the cupboard topples because there is a net torque due to the friction and the force you apply. When pushed ...
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Force in the Casimir effect
In the Casimir effect, after performing the regularization, it is found that the zero point energy between two conducting plates in a distance $L$ from eachother is (in the 1D case),
$$E=-\frac{\hbar ...
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Fluid mechanics and statics [closed]
I wanted to ask if I can use this law $P=\rho gh$
to compare between the pressure of two solid irregular cylinders (they don't have the same area above and at the bottom) but they do have the same ...
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Electromagnetic Stress Energy Tensor in terms of the potential
On a problem, I'm working on calculating the electromagnetic force in the absence of charge distribution with Maxwell's Electric Stress Tensor.
$F=\int d^3r \nabla\cdot \stackrel{\leftrightarrow}{T}=\...
