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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Single fundamental force at Planck epoch?

It is hypothese that after big bang when universe is a Planck time old, the 4 known fundamental forces used to be equal in strength or perhaps there existed single fundamental force before splitting ...
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2answers
97 views

Work and Free Body Diagrams

I am a bit confused with how to find work when there is a free body diagram. I am trying to work out this problem, and in it a box is being pulled at a constant speed by a rope at a constant angle ...
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0answers
19 views

What kind of forces would follow only the second part of shell theorem?

General expression of a force which would cancel out inside a uniform hollow shell. What about any closed surface?
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3answers
37 views

How does $p=fv$ hold when $v=0$ and an engine is working?

Standard high school equations: Work = Force x Distance Power = Work / Time = Force x Distance / Time = Force x Velocity When a space rocket takes ...
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7answers
3k views

Does it take more energy to open a door when applying force close to the hinge?

Assuming an ordinary hinged door (without any springs), would it take more energy to open it when applying force in the middle of the door (point b), rather than at the end of the door (point a), ...
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1answer
765 views

How to calculate the supporting force exerted by a stationary object (cupboard) and support (brackets) for it?

I have a wall mounted Stuva Ikea cupboard, which measures 60x64x30cm. The base is 64x30cm. It is already supported by 2 holes at the back base, (64x60cm). But I need to add in L shape brackets ...
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1answer
19 views

Contact forces and the structure of matter

Textbooks on introductory physics depict friction force as a result of interatomic forces. Matter is made of atoms and those atoms have eletric bounds. In turn, those eletric bounds are responsible ...
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10answers
16k views

How exactly does curved space-time describe the force of gravity?

I understand that people explain (in layman's terms at least) that the presence of mass "warps" space-time geometry, and this causes gravity. I have also of course heard the analogy of a blanket or ...
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5answers
69 views

Which one acts first: friction or tension?

I have a block kept on a rough surface with a string attaching it to the wall. I pull the block opposite to the string with a certain force $F \leq \mu mg$ where $\mu$ is the coefficient of friction ...
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2answers
2k views

Homework Question Transformation Energy [closed]

A $1400kg$ car is approaching the hill shown in the figure at $14.0m/s$ when it suddenly runs out of gas. What is the car's speed after coasting down the other side? I think I have to use this ...
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1answer
26 views

Calculating wind force and drag force on a falling object

I'm trying to numerically integrate the motion of an object (say, a falling vertical cylinder). Here, there's a drag force: the wind "acting" on the body (presumably adding horizontal velocity) and ...
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1answer
35 views

if you have an object on an inclined slope, by applying a horizontal force would you be able to lift the object from the slope?

I am programming a free body force diagram and as part of it a am allowing the user to adjust the angle of the plane and apply a force to an object on such plane at any angle to the horizontal. My ...
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0answers
29 views

How does force transmit through a solid block?

If you take a solid block, say, a cube of side length $l$ with density $\rho$, you place it upon a solid floor, and you apply an external pressure of $p(x,y)$ on the upper face ($x$ and $y$ define a ...
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2answers
515 views

Drag force on a flat plate

The solution for this apparently is $\frac{1}{2}C \rho A V^{2}$ where $C$ is the drag coefficient, $A$ is the area and $\rho$ and $V$ are the wind density and velocity. Let's do it without the drag ...
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2answers
42 views

Force when distance between charge is zero

According to coulomb law $$ F = \frac{q_1q_2}{r^2} $$ I want to know what happens to force when $r=0$. If $F \to \infty$ then the charges can't be separated! But if an unlike charge of higher ...
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1answer
129 views

Force field for Calcium ions, potassium ions and water in molecular dynamics

I want to adapt my existing MD simulation so that it can handle these three species. For the interactions of the ions I thought that I would use the coulomb potential, but I don't know what sort of ...
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0answers
30 views

Why doesn't a nuclear reactor's filament deform?

Why doesn't a nuclear reactor's filament deform? The filament in the core of a nuclear reactor is usually made of uranium rods. So in the nuclear reactions the neutrons constantly move from filament ...
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1answer
40 views

Lead bullet vs a Rubber bullet?

Our teacher says that rubber bullet is more effective than a lead bullet for knocking down a bear/human/whatever. He says that change in momentum for rubber bullet is greater than that for lead ...
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5answers
189 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 $75~\text{m}$?
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1answer
25 views

What is a “Reversed Effective Force”?

I have some confusion about the "Reversed effective force" as it appears in the derivation of D'Alembert's principle. First I have sources that seem to be contradictory. ...
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3answers
332 views

How do electrons actually move in a circuit?

Last year, we were taught about electricity, about how electrons move in a closed circuit. But as our teacher had not taught us about electric fields yet, she gave us a simplified model of motion of ...
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2answers
38 views

Why taking components of a component of a vector is invalid?

Suppose there's a force $F$ of magnitude 10 newtons in the direction of positive y-axis acting on a particle A. I know that the particle would not experience any force in the positive x-direction ...
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5answers
3k views

Is the EmDrive, or “Relativity Drive” possible?

In 2006, New Scientist magazine published an article titled Relativity drive: The end of wings and wheels1 [1] about the EmDrive [Wikipedia] which stirred up a fair degree of controversy and some ...
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3answers
124 views

Are circles stronger than triangles?

I've often herd in engineering that "there is no shape stronger than a triangle". I also recall that arches are very strong shapes as well, which can be crudely described as a ...
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0answers
31 views

Tensions in a rope [duplicate]

If two tensions are acting on a rope such that they are equal (each is 10 N) and opposite (180 degrees) then what will be the total tension in the rope? I cant seem to figure out if these two will ...
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0answers
23 views

Forces in equilibrium [on hold]

A homogenous beam OA with the length 4a and the mass m can rotate i the vertical plane around a horisontal axis through O and is kept in equilibrium by a wire attached in the points A and C going ...
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2answers
224 views

Advantages/Disadvantages of “hanging off” a motorcycle when leaning

The closest question I could find with regards to this subject was this one: Countersteering a motorcycle However, it does not address the specific physics of what I would like to know. There are 3 ...
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1answer
37 views

Good way to compute the force of a hammer blow?

What is a good and easy way to compute and/or measure the force of a hammer blow, not using any fancy or specialized equipment? If the hammer is swung by hand through an arc, it is not obvious to me ...
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1answer
42 views

Determine center of mass! [closed]

See the very funny figure. I have determined the mass of center in the x-coordinate to $r/4$ but I don't know how to get the y-coordinate. The key says it's $- r/ \pi$ but I can't see how to get ...
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2answers
156 views

Ball flying towards me - Newton's third law is violated?

I was trying to answer the question of the flying ball here on the basis of Newtons third law and Momentum conservation. Here is what I have tried. Lets take $m_1$ (the ball) hits $m_2$ (the man). ...
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2answers
120 views

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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2answers
41 views

First-principles derivation of cutting force

I know that the amount of force required to separate a material from itself is linked to the surface energy of that material. However, looking at just the surface energy laughably underestimates the ...
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2answers
91 views

Maximum Extension of a Spring [closed]

In the given figure: m= 5kg, F = 30N, K = 700N/m In the figure shown above. the surfaces are friction-less. The blocks are initially at rest and the spring is initially in its natural length. What ...
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1answer
140 views

How did Feynman prove that energy cannot be extracted from electric field?

In the Feynman Lectures, vol. II, chapter 4, Feynman discusses electric potential and says: If we carry a charge from point $a \to b$, $$W = -\int_{a}^{b} \mathbf{F} \cdot ds.$$ Now, in general, ...
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1answer
38 views

Help calculating work done by stretching a wire [closed]

A wire of length 0.89 m and cross-sectional area 1.7 cm2 is stretched elastically by an amount 1.2 cm. By Hooke’s law, the restoring force is $−k\Delta L$. Calculate the work done in ...
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3answers
94 views

Does dark energy work like gravity, but the opposite way?

If a body has more mass gravity will exert a greater force on it. Does that apply also to dark energy? In other words, if a body has more mass, will it be affected more by dark energy? (that is, will ...
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2answers
158 views

How to calculate the force acting on a magnet due to a solenoid

Can I assume both magnet and solenoid as magnetic dipole and use Coulombs law to find the force acting the magnet?
2
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1answer
76 views

How much weight would I need to put on the end of a tube to break it?

Say I have a tube with a circular cross-section made from some material (for an example, I'd like to use acrylic). I support it horizontally from one end and hang a weight from the other end. How ...
8
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4answers
2k views

How far does a trampoline vertically deform based on the mass of the object?

If a baseball is dropped on a trampoline, the point under the object will move a certain distance downward before starting to travel upward again. If a bowling ball is dropped, it will deform further ...
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5answers
87 views

How to interpret that forces do not depend on acceleration?

I was told forces can depend on time, location and velocity, but never on acceleration. At first I thought this must be wrong, thinking of $F=m\cdot a$. But I think/hope I now got what was meant, what ...
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1answer
36 views

If the cord has a breaking strength of 25.0 N, explain why the cord broke when supporting a load so much lesser than its breaking strength [closed]

A picture of weight 5.0 N is suspended from a hook on the wall by a cord. The tension of the cord is 7.07 N. It was found that the picture is hung too low on the wall and was adjusted by shortening ...
1
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1answer
125 views

Truck driven from a small motor that can carry a heavy load, yet can travel fast. [closed]

I am building a truck from trash as materials. I have one small motor and a a few small gears, but no other engineered materials are allowed. The truck must carry a load for a distance of 3m. The ...
0
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1answer
77 views

Gravitinos the key to theory of everything?

Theory of everything The theory of everything aims to unite all the four forces of nature into one single elegant equation. Super-symmetry Super-symmetry is important as it explains the nature of ...
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1answer
169 views

Force problem related to adhesive and bonding

I have two PCBs (printed circuit board), and they are glued by adhesives, as show in the pictures. And the location of the adhesives are indicated on the picture (please notice that NO adhesive is ...
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2answers
45 views

What guarantees that in a circular motion in a vertical loop, the resultant of the forces will always point to the center?

Here's what I know: If a body moves in a circular trajectory, then the resultant of all the forces must point to the center of the circle it describes in its movement. If a body moves in a vertical ...
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1answer
58 views

Confusion about average force applied over a time interval

If I understand correctly, the word average implies the average of forces acting during a certain time. $$F_{avg}=\frac{\int_{t_i}^{t_f}{F(t)\,dt}}{t_f-t_i}$$ The teacher gave us tasks with answers ...
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1answer
35 views

The force on the northern hemisphere

I am reading Griffiths' Introduction to Electrodynamics. On page 364, example 8.2 (4th edition), he calculates the force on the northern hemisphere of a ball with total charge $Q$ spread uniformly. ...
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2answers
103 views

When a force pushes an object does the force move the object? [closed]

When a force pushes an object from a point $a$ to a point $b$ does this mean that necessary the force moves the object?
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0answers
30 views

What will happen when an unstoppable force meets an immovable object? [duplicate]

I was thinking when this question came to my mind. What will happen when an unstoppable force meets an immovable object?
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2answers
87 views

Why liquids in hydrostatic equilibrium stay at the same height? (open tubes)

This part of the book says that, because the two liquids have the same pressure at the same height (that's true), then if a liquid has a higher height, the liquid would have more pressure at a ...