# Tagged Questions

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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### Is there a normal downward force here?

Now through my understanding, there is a weight force that points downward on block A, also another weight force that points downward on block B. Between block A and block B, there is two normal ...
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### Stick stands in the corner then starts to fall, when will it detach from the wall? [duplicate]

A thin homogeneous stick stands on the smooth(no friction) floor, leaning against a smooth wall,stands absolutely vertically. (Imagine a corner).Then it starts to fall(with zero initial velocity).What ...
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### Gravitation is not force?

Einstein said that gravity can be looked at as curvature in space- time and not as a force that is acting between bodies. (Actually what Einstein said was that gravity was curvature in space-time and ...
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### Pulley system on a double inclined plane [closed]

(Lets say, say static friction is $\mu_s$, and kinetic friction is $\mu_k$ for both of them) What is the detailed definition of static friction according to this picture? When the system starts to ...
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### Is there any case in classical mechanics where Newton's (strong) third law doesn't hold?

Is there any case in classical (non relativistic) mechanics where the strong form of Newton's third law does not hold (that is, reaction forces are not collinear)? For example, if we consider a system ...
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### Why does a teeter-totter (see-saw) tend to incline towards the heavier end?

Why does a teeter-totter (see-saw) tend to incline towards the heavier end? Since objects of different mass tend to fall at the same speed (assuming a vacuum), why do then heavier objects push harder ...
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### Understanding rocket equations [closed]

I'm doing a science project where I have to explain the physics behind a trip to an exoplanet and I also have to explain about rocket equations while doing so. I know that a trip to an exoplanet is ...
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### How to use an accelerometer to correctly quantify the magnitude of vibrations

Consider the following setup: An accelerometer is placed inside a helicopter, measuring $g$ values along three axes $(x,y,z)$ every $10~\text{ms}$ (100 times a second), during a helicopter flight. ...
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### Experiment to show $a \propto F$

I learnt about an experiment to show that acceleration is proportional to force. It was done by placing a trolley (like a toy car) on a smooth track. At the end of the smooth horizontal track was a ...
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### Inclined plane problem [closed]

This is the problem question from my textbook. My questions are concerning some formulas related to this problem. The force of friction is obviously down the plane. My initial question is: ...
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### Why do we talk of the “weakness of gravity” rather than “the surprising charge to mass ratio of particles”?

The relative strength of gravity and electromagnetic forces is obvious — stand on a sheet of paper, and even with the whole of Earth pulling, your motion is stopped by the electric fields inside that ...
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### F=ma is true in an accelerating coordinate system [closed]

There are plenty of similar topics about the physical or intuitive meaning of the equivalence principle or statement such as ''laws of physics are true in every frame of reference''. Usually answers ...
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### Newton's 3rd law applied to friction

I'm confused about how Newton's 3rd law applies to friction. If you slid an object across a table then the particles you are sliding against would exert the same force back, but wouldn`t this mean ...
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### Why doesn't gravity have charges?

All other forces have some kind of charge system, electromagnetism has positive and negative, weak force has hypercharges, and strong force has colors. Why doesn't gravity have anything like these?
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### Equilibrium equations

You have one horizontal beam. Its left point is attached to a free pivot at the vertical wall. Its right point is suspended by a rope from the ceiling. Nothing is moved. So $\sum F=0$ and $\sum M=0$. ...
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### If an object has a constant force being applied to it perpendicular to gravity, will the object fall slower?

If this was on a hypothetical flat plane (so not curved like the earth) and a rocket is flying horizontally, would the horizontal propulsion slow down the rocket's descent or even stop it from falling ...
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### Accelerated flow [closed]

Consider the following two cases: 1. Flow past a body, which is in constant acceleration and 2. Constantly accelerated flow over the body when it is fixed. Will the forces experienced by body in both ...
13k views

### If gravity isn't a force, then why do we learn in school that it is?

I have studied some of Einstein's Theory of General Relativity, and I understand that it states that gravity isn't a force but rather the effects of objects curving space-time. If this is true, then ...
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### Will loss of contact with the ground remove friction forces?

If we suppose that one object is losing contact from the floor, let's say the trajectory of this object is a semisphere, then in this instantaneous time just before the contact is loss will make the ...
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### in Newtons 3rd law, where does the second body get its energy to react?

A very basic question, and apologies if I have overlooked something obvious. In newtons 3rd law, presumably energy is transfered to the second body from the first body (which itself was subject to an ...
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### Falling Raindrop with Asymptotic Acceleration [closed]

I am given a falling raindrop that is gaining mass proportional to the product of its surface area and its velocity. I am assuming down is the positive direction. So, $m'=4\pi\alpha r^2v$. From ...
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### Finding the force between parallel currents using the formula of magnetic pressure

Let there be two parallel current-carrying infinitely-long wires separated by $d$ carrying currents $i_1$ & $i_2$ respectively in the same direction. In order to find the force on an ...
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### Equation of motion for ice block in water

I need to derive the equation of motion for an building block of ice that swims in water. The building block has an initial height that is looking out of the water called $h_A$ and is pushed into the ...
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### Spring Constant of a Slingshot

So we have a elastic slingshot which slides a block across the floor until coming to a stop but we've been facing a couple difficulties in determining our spring constant. We have a table of forces ...
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### Confusion about two-force members

This is my first question here so I hope I get warmly welcomed by answers that would resolve this perplexion :-) This is a statics problem from Hibbeler's Mechanics for Engineers: Statics (13th ...
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### Resultant force on the side of a tank of water

A closed tank rectangular in plan with vertical sides is 1.8m deep and contains water to a depth of 1.2m. Air is pumped into the space above the water until the air pressure is 35kN/m2. If the ...
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### Force required to send ball in set trajectory

If I have a desired 2D trajectory where I know the desired speed of my ball and desired path, and a ball that starts at (x=0,y=0), how can I calculate the required force / point at which the force ...