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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2answers
546 views

Toy helicopters at very high altitude

Because air is thin up there, toy helicopters usually have a maximum operational altitude. If the toy brought up by a real aircraft, higher than its intended maximum altitude, would it be able to ...
2
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0answers
1k views

How to calculate mass from compound lever? [closed]

A class 1 lever and a class 2 lever are connected in series, on the resistance end of the class one lever is a 500g weight. On the 2nd class lever sits a weight of an unknown mass. From the end of the ...
1
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2answers
1k views

How much force is required to compress air?

How much force (Newtons) is required to compress normal air in a chamber to 2 atm? For example, if I had a sealed piston pump, how much force would need to be exerted in order for the air to be ...
1
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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
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2answers
58 views

Why do we have a galactic and a solar plane [duplicate]

Why do all of the planets in our solar system move is (more or less) the same plane? It would seem that the planets should all have very different orbital planes, each at a different angel to each ...
1
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1answer
506 views

Inclined plane question [closed]

An object, mass $m$ is placed on an incline, angle $\theta$. System is at equilibrium. coefficients of static and kinetic frictions are $\mu_s$ and $\mu_k$ respectively. Then: 1) What is the Total ...
3
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3answers
3k views

How do forces work

Is there a mechanistic-type explanation for how forces work? For example, two electrons repel each other. How does that happen? Other than saying that there are force fields that exert forces, how ...
3
votes
2answers
72 views

Does Coriolis effect affect snowing?

Right now, outside is snowing. No matter what window I look from, the snow constantly for last few hours tends to fall to the right close to the window, and to the left close to the building across ...
0
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1answer
207 views

What forces are involved in this situation?

A old massless rope of 12 meters attached to a ceiling can sustain a maximum tension force of 1200N before breaking. An 85 kg person climbs up the rope. What is the minimum possible time in which ...
1
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0answers
186 views

Currents and magnetic fields produce forces that affect things they're not touching?

I was doing this past paper and am a little confused by question 5) part c)ii) I correctly calculated that the force acting on the rod due to the magnetic field is 0.016N but I can't see how ...
1
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1answer
259 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
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10answers
5k views

Should you really lean into a punch?

There's a conventional wisdom that the best way to minimize the force impact of a punch to the head is to lean into it, rather than away from it. Is it true? If so, why? EDIT: Hard to search for ...
0
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1answer
115 views

Magnetic Attraction in Space [closed]

If I were to attach a 1 inch diameter magnet to lets say a half pipe, that it fits perfectly in, and attach a 1 in diameter piece of iron close enough for the magnet to assert its attractive pull, ...
1
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4answers
1k views

Can you lift yourself standing on a wooden block using pulley mounted on block? [duplicate]

I am new to this site. Please help me figure out this problem. Is it possible to lift oneself like shown in schematic? Waiting for good suggestions. Chirag
2
votes
2answers
351 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 ...
1
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2answers
406 views

Can an extremely small force lift a mountain in a hydraulic system? If not, then why not?

As you see in the picture, a car can be lifted with a small force F1. Here it is shown that 'F1 . A1 = F2 . A2'. What will happen if A1 is of the size of a pin's cross-sectional area. Can a child ...
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4answers
2k views

Action and reaction pair problem

If I sit on a chair, the first action and reaction pair force is my weight and the force acting on the earth by me. And the 2nd pair is the force acting on the chair by me and the opposite force. ...
0
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2answers
272 views

Force acting on center of mass

Pictured above is a biker (traveling in a curve) whose center of mass has two forces acting on it. These two forces - a horizontal centrifugal force F(centripetal)* and a vertical gravitational ...
2
votes
2answers
422 views

What happens to gravity in the middle of the earth? [duplicate]

So I was curious about, what if we make a tunnel from one side of the earth, to the other side of the earth? Gravity is ofcourse always negative, which makes you "fall" and not "float". If we take ...
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2answers
3k views

Explain what happens to object in lift [closed]

In the following image,three cases have been mentioned. $N$ is the normal force acting on the object inside the lift and $mg$ is the force of attraction due to gravity. In case 1, $N = mg$. In case ...
0
votes
1answer
7k views

When to use Cosine or Sine? [closed]

Three blocks of masses $M_A=15.0 \; \text{kg}$, $M_B=12.0 \; \text{kg}$, and $M_C=8.0 \; \text{kg}$ sit next to each other on a frictionless surface. A force $F=54.0 \; \text{N}$ acts on Block $A$ ...
3
votes
1answer
2k views

Escape velocity of a rocket standing on Ganymede (Moon of Jupiter)

I want to calculate the escape velocity of a rocket, standing on the surface of Ganymede (moon of Jupiter) and trying to leave Ganymede. My thinking was, the kinetic energy $E_{\text{KIN}}$ must be ...
19
votes
5answers
716 views

Particles for all forces: how do they know where to go, and what to avoid?

Here's an intuitive problem which I can't get around, can someone please explain it? Consider a proton P and an electron E moving through the electromagnetic field (or other particles for other ...
15
votes
6answers
2k views

Are there forces which do not involve a change in momentum?

I am familiar with the equation $$\vec{F}=m \vec{a}$$ I am wondering as to whether it is possible for something to exert a force on another object without changing the momentum of said object. My ...
3
votes
2answers
1k views

What happens when the string slackens during vertical circular motion?

Consider a particle attached to one end of a string of length $l$ moving anti-clockwise in a vertical circle whose centre is $O$. What exactly happens physically when the string becomes slack and ...
17
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4answers
5k views

How can we move an object with zero velocity?

Consider there is a box of mass $m$ at rest on the floor. Most books give an example that we need to do a work of $mgh$ to lift the box $h$ upward. If we analyze this work done, the external force ...
0
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2answers
137 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 ...
3
votes
1answer
97 views

Mathematically impossible for a vortex line to have loose ends?

Could someone show the math behind it? Source : "A vortex is a bunch of air circulating around itself. The axis around which the air is rotating is called a vortex line. It is mathematically ...
-1
votes
1answer
178 views

Work Power & Energy Question [closed]

If a person starts from rest with an acceleration of 10 m/s^2 and applies force of 1000N then What will be its work done at the end of 20s . If the object moves in the horizontal surface? Can ...
0
votes
0answers
636 views

Why friction force is force of constraint?

My understanding about constraint force is that it is a force which limits the geometry of particle's motion. For example, situations such as the particle trapped in a track or limited in domain can ...
0
votes
0answers
95 views

Why does air circulate on an airfoil — The Kutta Condition [duplicate]

Why does the air circulate on a flowing airfoil, thus giving rise to increased velocity (circulation + relative airspeed) above the wing and hence decreased pressure.
0
votes
1answer
208 views

Do we stand on the earth because of Newton's third law?

This is the question I encountered and I'm not sure I understand. The Newton's third law say that, when a body 1 exerts a force on the body 2, then the body 2 will exert the same force on body 1, ...
0
votes
1answer
159 views

Airfoil theory — Why does air travel faster above? [duplicate]

I do not understand, why the air above the airfoil travels faster than the air below it? The air above has to travel faster than the air below so that both streams meet simultaneously at the ...
9
votes
2answers
335 views

Why don't black holes form from forces other than gravity?

Gravity is the weakest of the fundamental forces, so what is so special about gravity that it can form an inescapably strong field while a force like the EM force cannot? It seems to me that if there ...
1
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2answers
197 views

Estimation nuclear force between proton and neutron in deuteron

Is there an estimation of nuclear force between proton and neutron in deuteron to say What is the strong nuclear force between them? 1N? 10N? 100N? 1000N?
1
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2answers
676 views

What is the third law action pair of buoyancy?

Consider a block floating in a fluid. The force due to gravity balances the buoyant force exerted on the block. But there must be a third-law action pair to the buoyant force. If the block exerts a ...
0
votes
1answer
184 views

How do magnetic objects exhibit attraction/repulsion across empty space?

Magnets will attract or repel over a distance before physically touching each other. What makes this effect possible? My best guess is that the forces generated by the angular momentum of the ...
1
vote
1answer
838 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
3answers
302 views

Why does centre of mass of ice-container system shift in absence of any net external force?

Consider a cube of ice in a flat based container(the base is very broad).The temperature of the system is at first fixed at a minus Celsius temperature, but then the system is left on a table with the ...
1
vote
1answer
570 views

Where do these formulas for an object being pushed up an incline come from? [closed]

An object on an incline with an angle $\theta$ is being pushed at constant speed. Constant speed implies $a = 0$. Because $F=ma$ and the object must have mass greater than 0. If I want to find the ...
2
votes
3answers
81k views

Tension on a string between two objects on a friction less surface [closed]

I just need my work checked here. Please let me know if I am correct. I had this problem in one of my test in which I did not get full credits. I am re-doing this(hopefully correctly this time) just ...
0
votes
0answers
91 views

Questions on electron orbits

I have three questions to ask: Why do electrons (in an atom) specifically move in orbits and not some other type of motion? Where does the energy comes from, for the electron to move at much higher ...
0
votes
1answer
130 views

Why is it easier to turn a heavy hanging object?

Assume if we had a 2 tonne weight placed on ground attached with a rope that we can use to turn the object around. It will immensely hard to turn that object around by pulling the rope. However, if ...
0
votes
2answers
222 views

Equal and opposite reaction - forces coming in pairs - or just common sense?

I've never understood why the conservation of momentum law is taught in schools as "every force has an equal opposite reaction". To me a gun's recoil is self explanatory; the explosion sits ...
0
votes
0answers
33 views

How to measure power used to sustain something in a (gravitational) field? [duplicate]

I've read this question and answers, but neither of the posts does seem to address my concerns. The problem is as follows: Assuming a device that keeps something in a gravitational field on a ...
2
votes
2answers
2k views

Solving actual weight lifted

I was wondering if anyone knew the formula to calculate how much force is required to lift a tire or any object by the edge. For example if a tire weighs 500 lbs (or has a mass of 226.8 kg). I would ...
41
votes
6answers
8k views

Pouring water in an aircraft while upside down?

What is the physics behind the following photo? Someone had told me that this is because the aircraft might be moving towards a lower altitude, but I am still not sure.
0
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1answer
2k views

The nature of the gravity force: Is it attractive or repulsive between positive and negative mass? [duplicate]

If negative mass is rotating around fixed positive mass, then what will be the nature of force and how?
31
votes
5answers
5k views

Why isn't Higgs coupling considered a fifth fundamental force?

When I first learned about the four fundamental forces of nature, I assumed that they were just the only four kind of interactions there were. But after learning a little field theory, there are many ...
9
votes
1answer
91 views

More forces at low energy?

Just a quick question: In high energy experiments, the fundamental forces are thought to merge into a single force. My question is, in very low energy experiments (very low), do the forces we know ...