# 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 the other 3 fundamental forces also warp space-time?

I got this idea from Einstein's insight using the falling elevator. He says, that Gravity really cannot be distinguished from any other force accelerating the elevator. A bunch of questions on here (...
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### Do forces get affected by relativity?

Do forces change their behavior due to the relativity? For example if a charged particle deflects through an electric field, would the pattern and amount of deflection differ in speeds near speed of ...
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### Why do you feel the difference in the force required when a muscle contracts and relaxes even if you apply the same force to an object?

Think about a person lifting or lowering a 50kg object vertically. Lift and lower at constant speed. At this time, the force exchanged between the person and the object is 490 N, and the person is ...
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### Painter on scalffold - Kleppner and Kolenkow Problem 2.12 [closed]

I am currently trying to teach myself mechanics by reading Kleppner and Kolenkow's Introduction to Mechanics, and I've hit a bit of a snag on Problem 2.12. A painter of mass M stands on a scaffold of ...
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### On the infinite range of the electromagnetic force

I am curious as to whether there is a fundamental reason why weak and strong nuclear forces have such a short range whereas gravity and the electromagnetic force seem to have infinite range. Since ...
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### Can there be acceleration without work?

Since $W=Fs$, $F=\frac{W}{s}$. When you substitute this in the formula for acceleration, $a=\frac{F}{m}$, you will get that $a=\frac{W}{ms}$. Then, when work equals zero, acceleration will be zero.
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### Are the three effects equivalent? [closed]

(Due to my lack of ability, there are many sloppy parts in the question.) I am a beginner in physics. After reading a little about thermodynamics, quantum mechanics and general relativity, especially ...
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### Conservation of momentum vs newton's second law

I saw this question from a book: An empty sled is sliding on frictionless ice when Susan drops vertically from a tree down onto the sled. When she lands, does the sled speed up, slow down, or keep the ...
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### Force between two wires at an angle [closed]

I want to find a simple model for the force between two cylindrical permanent magnets that are at an angle $\theta$ and at their closest point a distance $L$ from each other. For this I want to ...
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1 vote
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### Is Energy stored Force?

I am currently studying the relationships between energy work and force. I am trying to conceptualize them into one concept of causality. When a force is applied work is done, and energy is ...
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### Follow up question on a block on an accelerating inclined plane

A follow-up on this post: How can an accelerating inclined plane prevent a block on it from sliding? Farcher's answer states that "If F is larger than in the no relative movement condition then ...
1 vote
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### Hard problem of pulleys [closed]

A string passes over a frictionless, massless pulley attached to the ceiling A mass $m_1$ hangs from one end of this string, and a second massless, frictionless pulley hangs from the other end. A ...
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### Why do cars move slightly backwards just before coming to rest?

You've probably noticed this before: you're in a car or other wheeled vehicle, the brakes are applied, the car's velocity reaches zero, and then the car actually moves backward a tiny amount before it ...
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### Force between two antiparallel magnetic point dipoles

How can I calculate the force between two antiparallel magnetic point dipoles with their magnetisations pointing towards each other. I know the derivation for the force between two electric point ...
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### Classical mechanics problem of elevators [closed]

A passenger elevator consists of an elevator cage of 900 kg (empty) and a counterweight of 990 kg connected by a cable running over a pair of pulleys (Figure 6.9). Neglect the masses of the cable and ...
1 vote
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### Proof of principle of transmissibility of force

The principle of transmissibility states The point of application of a force to a rigid body can be moved anywhere along its line of action without changing the external reaction forces. My question ...
1 vote
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### Friction Force from Rubber Band [closed]

Consider the following problem from the 2022 A F=ma exam: The correct answer is A, but the answer I get is off by a factor of 2. The way I did it was to treat the rubber band as a regular polygon ...
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### Is Newton's laws formulated using laboratory time?

The second Newton's law can be written as (in SI units) $$\frac{d}{dt}\vec p = \vec F.$$ Newton was considered Galilean transformations and the existence of a "absolute" time. Now suppose ...
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### Average Tension in the string of a pendulum: Determining radial component of weight

Self-studying Classical Mechanics right now and was working through an example until I got to a point where I felt certain questions need be addressed. I will list the problem statement, the example ...
1 vote
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### Average Tension in pendulum string: Understanding the radial $F = ma$ equation

Self-studying Classical Mechanics right now and was working through an example until I got to a point where I felt certain questions need be addressed. I will list the problem statement, the example ...
1 vote
38 views

### What causes the difference in ranges of forces?

What causes the difference in ranges of forces? In other words, why is it that the weak force acts only at small distances whereas the Coulomb force has a very large range?
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### Resolution of force vectors

So, I have had this query for like the longest time, ever since I first studied this topic. So, take a force vector $F$ that is making an angle of say, 30 degrees with the horizontal axis. Now, I want ...
1 vote
31 views

### Use of Instantaneous axis of rotation (IAOR) in a question of mechanics give different and wrong answer

The above situation can be solved easily when we go in frame of point C then point C will come at rest and mass "m" will do circular motion about point C with 3v velocity and then using ...
1 vote
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### The force distribution along curved surface of contact [closed]

Is it possible to calculate the stress or contact force distribution over a curved contact surface? I will try to explain the general idea in the figure below. Object $O$ (could be assumed to be rigid ...
1 vote
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### Law of inertia in rotation

Consider an object rotating about its own axis. If the law of inertia is applicable, the object should keep rotating with the same angular velocity if no external torque is provided, but how is the ...
1 vote
29 views

### Can a bicycle whose front wheel cannot turn left/right stay upright?

Most sensible explanations of why a bicycle stays upright involve the turning left/right of the front wheel. If a bicycle's front wheel cannot turn left/right, can it stay upright while being pedalled?...
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1 vote
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### Why don't we utilize centripetal acceleration for particle accelerators or ion thrusters?

Acceleration of an object in a circle is determined by its radius (r) and speed (v). Acceleration = (v²)/r So, acceleration is greater at high speeds and in sharp curves (smaller radius). Centripetal ... 1 vote
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### Magnetic force calculation for parallel wires using Maxwell stress tensor. Issue with shear forces

I am trying to calculate the forces in between permanent magnets and ferromagnetic surfaces with the Maxwell stress tensor using image theory and the Biot-Savart law. However I discovered a weird ...
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### Why is gravity not a force? [duplicate]

Gravitation is the mutual attraction of masses, yet Einstein showed it is how spacetime is curved by mass and how mass moves in relation to this curvature. Why then do we still consider gravitation a &...
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