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 ...

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4
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2answers
158 views

Why isn't the product rule used in the definition of mechanical work?

Mechanical power is normally defined as $P = \mathrm{d}W/\mathrm{d}t$, and work is normally defined as $W = \vec F \cdot \vec x$. Today an undergrad pointed out a confusion he had from Griffiths' ...
2
votes
2answers
236 views

Stable equilibrium given force

If a particle moves under the influence of a resistive force proportianal to velocity and a potential $U$, $$F(x,\dot x)=-b\dot x-\frac {\partial U}{\partial x}$$ Where b>0 and ...
0
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1answer
1k views

Relationship between angles [closed]

Question: Find the relationship between angles $\theta$ and $\phi$ using the equations of equilibrium and solve for $\theta$. Express your equation for $\theta$ in terms of $\phi$. ...
1
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2answers
242 views

Is there a definition of force? [duplicate]

Well, Newton's three laws talks about forces, but no definition is given. In truth, Newton's second law gives an idea of what total force is: the time change rate of momentum. But, if we have a force ...
0
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2answers
209 views

Power delivered by centripetal force

Does centripetal acceleration deliver power to the revolving object? What I think: Power is given by F.v Since for a body in circular motion velocity and acceleration are at 90 degrees the power ...
0
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2answers
7k views

Simple rope tension problem

I have this really simple rope tension problem that can be solved for seconds using simple logic. I know what the answer is, I know why it is, but I cannot write it down and explain it mathematically. ...
2
votes
0answers
47 views

Impact of friction on a fallen body [closed]

If a body travelling at speed falls to the ground through an arc from a certain height (someone walking who trips, for example), how does friction of the ground surface affect the forces impacting ...
2
votes
3answers
2k views

Pulley problem - unable to understand the concept

Given: The pulley is moving towards the right. All blocks have different masses. (The pulley and the strings are massless.) What I don't understand: Is the tension the same for both A and B? ...
0
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2answers
3k views

Two boxes that are connected pushed by force - what happens between two boxes?

So when two boxes are connected together, and force is applied, two boxes move with the same acceleration. (assuming force is constant.) My question is, how are forces between two boxes get cancelled ...
1
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1answer
38 views

Is it possible to float, starting at an elevated point, with a board and enough strength?

Premise: I have a structure like this. O _____ | | | | I'm the O, and I'm sitting on a flat surface or board ...
1
vote
1answer
111 views

How is the view of charge and forces in quantum mechanics different from classical physics?

I am taking an introductory course on quantum mechanics and would like to understand this. Do forces act in quantum mechanics? In orbitals, is the charge of an electron dispersed, with a higher ...
1
vote
1answer
2k views

Pulley and Two Masses: Why is the acceleration the same?

Say you have a massless string going over a pulley pulley attached to a cart on a frictionless surface one end, and a hanging mass on the other end. What guarantees that the cart and the hanging mass ...
2
votes
2answers
79 views

Can be the ionosphere described as an elecro-magnetic field?

I read that the ionosphere can be defined as plasma. it has its plasma frequency it has its Debye length it is overall neutral As it is overall neutral it does not produce any electric field. ...
5
votes
2answers
584 views

Force in Special Relativity

I have a question regarding how force on a body works in the framework of special relativity. As far as I am aware, the equation for force in special relativity is: $$F=m\alpha$$ Where $\alpha$ is the ...
0
votes
2answers
897 views

Lever Counterweight of uneven weight distances

So, I have a camera crane that has a pivot leaving 2 distances, 0.5mts and 1.5mts respectively. Plus a small L-shaped piece of metal and the end of d2 (1.5) which holds a camera, which I suppose I ...
3
votes
3answers
7k views

When a ball is tossed straight up, does it experience momentary equilibrium at top of its path?

This question has been asked many times all over the Internet and answers can be found on places such as yahoo and ask.com, but I'm not satisfied with those answers and I don't trust the validity of ...
-1
votes
1answer
144 views

Doubt in law of mutual interaction

Book: Classical mechanics (textbook) by Douglas Gregory (cambridge publications) Law of mutual interaction states that when two particle (let it be P1 and P2) interacts, the particle (P1) induces an ...
1
vote
1answer
1k views

Tension on pulleys Physics Question [closed]

Collar A is connected to a 50lb load on a frictionless horizontal rod. Determine magnitude of P to maintain equilibrium when x=4.5. Im confused on the concept of Tension I originally got the ...
1
vote
1answer
254 views

A question from a Physics 2 exam: About electron cloud an a constant external field:

I am trying to prepare for my exam in Physics $2$, the following is a question from an old exam (the question also have a detailed answer to it, but I don't really understand it). An acceptable ...
0
votes
2answers
128 views

what is “work”? (of a force)

I would like to know why two forces (of different magnitudes but same direction) that we'd use sequentially on an object to move it by the same amount twice, will produce two different values for the ...
0
votes
1answer
106 views

Combine forces (gravity)

I have a point at which there are (at least) two different forces (gravity to be precise) working. How do I combine those so that the force acting on the point are as realistic as possible? To put ...
0
votes
2answers
569 views

Force and Area are proportional to each other, but [closed]

I have read on book the next following sentence: The force is proportional to the area, for if we increase the area but keep the number of molecules per cubic centimeter the same, we increase the ...
0
votes
1answer
70 views

Force From Distance

I'm working on a physics engine for a game and I need something clarified. Let's say I have a stationary sphere, sitting atop a platform. The sphere's mass is 10kg, and gravity is $10m/s^2$, for the ...
-1
votes
1answer
3k views

Net torque on a frictionless pulley

If we consider a system comprising a massless string over a frictionless pulley,then we write the torque equation as $(T_2-T_1)R=I a$ ,where $T_2$ and $T_1$ are tensions on either side of the pulley. ...
1
vote
1answer
309 views

Thought experiment-shell theorem

Consider a uniformly dense perfectly spherical planet. At any point inside the planet, the gravitational attraction is only due to the mass below the point. (red circle) according to shell theorem. ...
0
votes
2answers
132 views

Can you justify force calculations using more than one of Newton's laws?

If an object is at rest on a flat surface I remember my school teacher would say, "By Newton's 1st law the normal reaction, R, is mg (mass x g)". Ok, sure this is fine because the object is at ...
1
vote
1answer
353 views

Variable Tension in the string [closed]

A body of mass $m$ is hanging with a string having linear mass density $\lambda$. What is the tension at point $A$ as shown in the figure. I am aware of the scenarios in which string is ...
2
votes
0answers
87 views

Consistency of equation with special relativity?

The following is the equation which, I want to know, if it is valid in relativistic domain. Consider two equal charges moving in same direction with velocity $v$ and charge $q$ at a separation of ...
0
votes
1answer
227 views

Free body diagram of rod in sphere

I was finding the free body diagram part of dynamics quite easy until I found this question , Here's how it goes : A rod AB is placed inside a spherical shell, whose inside surface is rough. Draw ...
0
votes
3answers
305 views

A few questions about the concept of work

From Wikipedia: The work done by a constant force of magnitude F on a point that moves a displacement d in the direction of the force is the product: $$W = Fd.$$ If I lift some object from a ground, ...
0
votes
1answer
490 views

Newton's Third Law and Constant Velocity

How can an object that's not accelerating cause another stationary object to move in a collision? This website: http://www.physicsclassroom.com/Class/momentum/U4l2a.cfm, says that a "rightward moving" ...
1
vote
4answers
610 views

Given Newton's Third Law, how can an inanimate object create a force?

Newton's Third Law states that Whenever any force is exerted by a body#1 on any other body#2, another force which is equal in magnitude and opposite in direction is exerted on body#1 by body#2. ...
8
votes
3answers
3k views

If atoms never “physically” touch each others, then how does matter-antimatter annihilation happen?

It is known that matter and antimatter annihilate each others when they "touch" each others. And as far as I know, the concept of "touching" as our brain gets it is not true on the atomic level since ...
2
votes
0answers
253 views

What is wrong with this downforce calculcation?

I tried calculating the downforce of a spoiler I need for a robot. I used this formula. $$F = \frac{1}{2}Ac_a\rho v^2$$ Where $\rho$ is air density, $v$ is the speed of my robot, $c_a$ is the lift ...
0
votes
3answers
86 views

Is it possible to reach the edge of a room if there isn't any gravitational acceleration?

Consider that a large room(an indoor badminton court) is orbiting the earth with a person floating exactly at its center without any relative initial velocity. Consider that the person has no ...
0
votes
2answers
10k views

Finding the drag force (Air resistance force) for accelerated ball?

As you know if I want to find the force for an accelerated object I will use the law $F_o=ma$ so I can get the affecting force of it. But there is another force affecting against the object. It's the ...
0
votes
0answers
25 views

What are physical effects that could be employed to emulate this system?

This is a simple system consisting of a tree of numbers such as ((1 2 (3 4)) (2 6) 1 6) and a rule of application, that states that a tree A applied to B is a copy ...
0
votes
2answers
459 views

Why do we say that in Coulomb's law the force is proportional to $\frac{1}{r^{2}}$ and not $\frac{1}{r^{3}}$?

I am going over Coulomb's law and there is something that is a bit confusing for me: According to Coulomb's law, if I have a charge $q_{1}$ at a point $\vec{r_{1}}$ and a charge $q_{2}$ at a point ...
1
vote
1answer
470 views

Dielectric slab counter-intuitive formula?

For the calculation of force on one of the two equal(in magnitude, opposite in sign) point charges separated by $r$ with a dielectric slab of dielectric constant $K$ and width $d$ in between, the ...
1
vote
1answer
353 views

How to sum several thrust vector on a single object (like a plane)

I'm a developer. I tried (mostly for fun) to create a realistic physic engine. I try to sum all forces (here thrust) applying to an object in two composantes: an acceleration vector and the angular ...
1
vote
2answers
319 views

Force on carabiner from free fall [closed]

Suppose I weigh about $75~\text{kg}$ and I am attached to a (non-elastic) rope which is attached to a carabiner which can take at least $20~\text{kN}$. Suppose furthermore that I reach terminal ...
0
votes
1answer
47 views

What portion of impulse is received by the cylinder?

Condition: A cylinder with a piston are situated along Y axis. Piston receives an impulse (P1) along Y axis and transmits it to the cylinder through a gas medium with which cylinder is filled. The ...
0
votes
1answer
196 views

Using Thrust from Air Pressure [closed]

Alright, so I've been messing around with turning air pressure into thrust, however I'm only a sophomore in high school, so my physics knowledge is fairly limited. (I've studied higher level physics, ...
1
vote
1answer
346 views

Particle slightly disturbed radially in stable circular motion under central force

A particle of mass $m$, moves around a central force whose potential is $$V(r) = kmr^3 \; (k>0),$$ then $(c)$ if the particle is slightly disturbed from the circular motion, what is the ...
1
vote
2answers
223 views

Steering forces on a bicycle

Ok, I always notice this weird thing and try to overcome it but cant. Ok as shown in the image when I ride the bike by just one hand and pull the handle back say from the right side so as commonly the ...
0
votes
1answer
708 views

Pulley problem with spring balance

Please excuse the crude drawings The question is, if I burn the thread t, how will the reading in the spring balance(S) change? Ie, increase, decrease, or remain the same? My approach: When we ...
0
votes
3answers
389 views

Do volcano blast changes earth's course?

Volcano blasts are one of the most powerful calamities on earth. When they blast they release large amount of mass in the air just like a jet does. Does such a blast have any effect on the course of ...
1
vote
1answer
494 views

Question about teeter totters or see saws

I have a basic enough question. Assume that one has one of those ideal see saws, i.e. the teeter-totter pivots on point source, the balance is of uniform mass etc. Now assume that one places an ...
0
votes
0answers
126 views

Collision of two deformable bodies - limitation of work-energy theorem

I am attempting to model the impact of a deformable body (clean, dry sand characterized as a continuous fluid) with flexible diaphragm (in this case a sheet of rubber). Assuming that this is a closed ...
2
votes
2answers
128 views

Wire forces in an inductor

For an inductor, the electromotive force comes from Faraday's law, as I understand it. The governing equation includes the number of turns, the magnetic flux (field and area), and a time ...