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 ...

learn more… | top users | synonyms (1)

1
vote
4answers
207 views

Why is force called the rate of change of momentum? [closed]

Why is force called the rate of change of momentum? If I push a wall I do exert a force but there is no movement; so is there force acting on the wall?
1
vote
1answer
281 views

Repulsive Force between two Electromagnets

This question might seem a bit too basic(or advanced!), but it is the one to which I'm really desperate to find a simple enough explanation and solution. Ok, So here's the problem, I have two ...
1
vote
1answer
687 views

How is the fall time for a parachute affected by the mass of the load?

Why do parachutes with a heavier load fall faster than a parachute with a lighter load?
1
vote
2answers
111 views

Why is sometimes more difficult to lift a baby?

I have a small cousin and she enjoys when I pick her up, which I can do pretty easily. Sometimes though she decides she wants to make my life difficult, and when she decides so, she tells me she is "...
1
vote
1answer
55 views

Extension spring and permanent damage

Is there a way to calculate how far an extension spring can be extended before it suffers permanent damage? There are some online calculators, but how are they done? This calculator is the most ...
1
vote
1answer
64 views

Why does the axle need to be rotated in a turbine generator?

Inside a turbine a wire rotates between the poles of a magnet, i.e. rotating inside the magnetic field, so that the field forces the electrons in the wire to move and generate current. But why does ...
1
vote
2answers
109 views

Why things wobble when submitted to wind?

If I place a little piece of paper in front of a fan, it is going to wobble/oscillate. Is it because the wind flow isn't constant ? Or because the air movement makes the piece of paper move away, so ...
1
vote
3answers
915 views

Tension in a rope

In an ideal case, we assume strings and ropes to be massless and having same tension throughout. However, I was doing some questions which involved a rope with mass. The question was that if a ...
1
vote
3answers
2k views

Calculate acceleration from power [closed]

I am currently programming a simple computer space ship simulation. This is just for fun to train my programming, 3D graphics and a little bit of physics skills. What I want is the user to pick a ...
1
vote
1answer
140 views

Work done by friction on a body?

I know that when a body slides over a surface, the work done by friction is not stored as potential energy in the body. It is dissipated in the form of heat. But why is it not stored as potential ...
1
vote
1answer
82 views

Would the Lorentz force of the two wires be different?

From the following diagram: Lorentz force can be calculated from the following formula: $F$ = $IL\times B$ What about this wire in the following diagram? Assuming that all the variables are the ...
1
vote
2answers
240 views

frictional force is nonconservative force [duplicate]

In nature there are mainly four kind of fundamental forces,electromagnetic force is one of them which is conservative force.If friction force is belongs to electromagnetic force then why it is not ...
1
vote
5answers
2k views

How can static friction do work?

By definition, the work done by a force is $W = F\cdot d$, so how can static friction do work? Can this force move the body a distance of $75~\text{m}$?
1
vote
2answers
119 views

How this formula for work follows from the definition?

If a particle moves along a path $\gamma : I\subset \mathbb{R}\to \mathbb{R}^3$ then the work done by a force $\mathbf{F}$ is defined by $$W = \int_{\gamma} \mathbf{F} = \int_{I}\mathbf{F}(\gamma(t))\...
1
vote
2answers
139 views

Is my answer possible? (Newtonian Third Law Pairs and Forces, Multiple Choice Word Problem)

So I recently took a test and the teacher graded my answer correct, yet my friends saw that the other answer was correct and they protest that it should be the right answer: The question goes: ...
1
vote
3answers
145 views

A problem related to Work done by falling bodies : Expert's attention much needed! [closed]

I'm having a lot of trouble with this question, that I've found in my textbook. I've solved it in my own way and it's very simple! But the solution in the book is totally different. It doesn't make ...
1
vote
1answer
162 views

Can gravitational force act as an impulsive force in any case? [closed]

Can gravitational force be termed as impulsive in any case? I' m thinking about it but couldn't get any answer. When two heavenly objects collide then the force exerted on each of them during the time ...
1
vote
2answers
151 views

Can magnetic force do work? [duplicate]

I have been told numerous times that magnetic force do no work at all but I have some trouble digesting this fact. Now suppose we have two straight wire with some current, they certainly can feel ...
1
vote
2answers
419 views

Force of a Train

Imagine that there are two trains and the first train is twice as long as the second train. They have the same mass per unit length and they are traveling at exactly the same speed. If the first ...
1
vote
1answer
181 views

How do you find the tension in the real world? (Given a rope in a pulley system)

I'm well aware of the formula to calculate tension, however, given a real world situation where you have a closed pulley system. How do you measure the force (i.e., tension) required to pull on the ...
1
vote
1answer
222 views

Why is the gravitational force $10^{38}$ times smaller than the strong nuclear force?

Also, why is the weak interaction force $10^7$ times smaller than the strong nuclear force?
1
vote
2answers
409 views

Modeling external forces in Lagrangian dynamics

For example, consider a system with a block on a flat, frictionless surface. On one side is a spring connecting the block to a wall. On the other side, a person's hand is pushing the block towards the ...
1
vote
2answers
100 views

Why do these two derivations of the formula for impulse contradict?

I was trying to derive $I = F\Delta T$ from $p = mv$. First I converted $v = at$: $$\begin{align} p &= mv \\ p &= m \times at \\ p &= ma \times t \\ p &= Ft \\ \Delta p &= F \...
1
vote
1answer
124 views

Disk and Ball on a smooth surface [closed]

A uniform disk of mass $\text{2m}$ and radius $\text{R}$ is placed freely on a smooth surface as shown in the figure. A particle of mass $\text{m}$ is connected to the circumference of the disc with a ...
1
vote
3answers
154 views

How are the half life of particles mathematically related to the inverse square laws?

This video https://www.youtube.com/watch?v=K6i-qE8AigE&list=PL3B0924C6A0CB8B67 explains how forces are boson particles. It talks about the other non-force particles giving off and creating bosons, ...
1
vote
1answer
130 views

Metallic coin over wooden block in glass of water

So there is some water inside a container; the height of water inside the container is $l$. I placed a wooden block on the water and it's floating to some height $x$, on top of the block is a metallic ...
1
vote
1answer
219 views

How much pressure do wheels exert on the ground?

I would like to know how much pressure 4 "rigid" wheels (as opposed to tyres) would exert on the ground; I've been on the case for hours now and the best I've come across to calculate this was the ...
1
vote
2answers
728 views

Repelling force of magnets

What happens if I take two strong magnets and press their like-poles towards each other - does the repelling force created by them equals the force I'm exerting on them or does the repulsion force ...
1
vote
5answers
4k views

How to find total force on an object?

If there are a multitude of forces acting on an object in different directions, how do we find the TOTAL force? I know we add up the $ x $- and $ y $-components of the forces individually, but how do ...
1
vote
1answer
3k views

Final velocity of a spring [closed]

I need to calculate the velocity of an object when it is thrown by a spring; we have to calculate the velocity from $U=\frac 12 kx^2$. Now I know that $U=L=F\cdot S$ and $S=\frac{v_f^2-v_0^2}{2a}$. ...
1
vote
1answer
362 views

How does the weight of the pendulum's bob cause a torque?

I know that a force will cause a torque if the force has a perpendicular component to the distance from the pivot point. However, in the figure above, I can't seem to visualize how the weight of this ...
1
vote
1answer
228 views

Electromagnet force equation clarification

So, from a previous previous question, I know what plane the force from an electromagnet will affect a ferromagnetic material in. I thought that would be enough, but working through some problems ...
1
vote
2answers
1k views

Force Diagram for K&K 2.13 [closed]

I have been (independently) working on Problem 2.13 in Kleppner and Kolenkow's An Introduction to Mechanics and come to an answer which conflicts with the hint the authors provided in the book. The ...
1
vote
1answer
227 views

What force counteracts friction when a block is pulled?

Firstly, I understand and apologize that this is more of a physics question than a math question. I noticed that when I pulled a book out from under a pack of gum, the gum stayed largely in place (it ...
1
vote
2answers
787 views

who will win a race between man, horse and car of same power

Other day I got into a chat with my friend on work power and energy where he asked an intelligence related question the question was like this if a race was conducted between a man a horse and a ...
1
vote
1answer
390 views

Will we feel the gravity of a star 10 light years away for the next 10 years if, somehow, it vanishes today from its position? [duplicate]

I was watching a relativity video, and although I am not sure, I felt that it was trying to tell that the effect of gravitation of a body is instantaneous, in the sense that a sudden change in the ...
1
vote
1answer
42 views

Clarification what exactly this question wants regarding force [closed]

I would like to ask you if the question asked What is the minimum force parallel to the plane, which can be prevent the block from slipping down the plane? I just did the calculation and and ...
1
vote
1answer
67 views

Help for orbits of planets

Suppose that an asteroid) that moves at a velocity $v$ passes near to a planet: now I know that the gravity force of the planet will curve the trajectory of the asteroid so I tried to make a draw of ...
1
vote
1answer
124 views

Motion of a car rounding a bank

When a car is traveling round a banked track as fast as possible, it has a tendency to slip up the slope. Opposite in the case when the car travels slowly and has a tendency to slip down. Can ...
1
vote
2answers
1k views

Upthrust vs Drag

24: A ball is falling at terminal speed in still air. The forces acting on it are upthrust, viscous drag and weight. What is the order of increasing magnitude of these 3 forces? ...
1
vote
2answers
894 views

Is the moment of a force the same about any point?

I know that when a body is is equilibrium There is zero resultant force in any direction, i.e. the sum of all the components of all the forces in any direction is zero The sum of the moments about ...
1
vote
2answers
132 views

Universal gravity at small distance

Could it be that there is simply a maximum gravitational force that two bodies of finite mass can exert on one another? This would occur at $r=0$, so maybe there is some really really really small $a$ ...
1
vote
1answer
1k views

Finding friction forces of stacked boxes on a table

Consider the following system. The given friction coefficients are for static. Let $g=10$ (meter per square second). If the $F(t)=10t$, for example, determine the friction forces $f_{AB}(t)$ (...
1
vote
1answer
83 views

How quickly does air return to a vacuum chamber?

I know there are a lot of variables that affect how quickly this would occur. Any information on the topic would be highly appreciated. For sake of argument, lets say 1 square foot chamber, lets say ...
1
vote
1answer
277 views

A question about biceps and rotational equilibrium

I know that as the angle of the elbow increases, the force of the bicep increases. i.e. when angle is 180, arm is fully extended and there is 0 force from bicep. When the elbow angle is smaller there ...
1
vote
1answer
868 views

Why does shaking your head with short hair hurt? [closed]

When my hair gets long I start doing a little flick of my head occasionally to get my hair out of my eyes. This grows into a habit though, and for the first few days after cutting my hair I end up ...
1
vote
1answer
75 views

What is the “inner” force behind attracion/repulsion?

First of all, I'm sorry for any grammatical big error - English is not my native language. I have a question that maybe does not have an answer beyond those which we already have, but maybe there is ...
1
vote
4answers
409 views

How much up will an object of mass $m$ will be vertically lifted if a constant acceleration $a$ is given so that resulting force is more than weight?

Yesterday My friend asked me a question which put me into a confused state. If a body of mass m is given a vertical thrust of $F$ such that $F > mg$, and the $F$ is allowed to remain applied on ...
1
vote
2answers
536 views

Minimum acceleration so that mass $m$ falls freely [closed]

A block of mass $m$ rests on a frictionless wedge of angle $\theta$ as in the figure. The wedge is given an acceleration $a$. What is the minimum value of $a$ so that the mass $m$ falls freely? I ...
1
vote
2answers
136 views

How far could one fire a charged particle in space?

I've wondered how far would be able to send a concentrated beam of electrons in space. The reason is would we be able to launch a magnetic ring with an electron absorbing material on one side and just ...