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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1answer
506 views

Accelerated wedge [closed]

Consider the following figure, where a mass $m$ is placed on a wedge which is accelerated to the right ($\vec a$) which could be negative. The coefficient of friction between the mass and the wedge ...
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3answers
954 views

Direction of friction force between two boxes

There are two boxes on top of each other. The bottom box is dragged right by a constant force. What is the direction of friction of the top box against the bottom box?
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2answers
2k views

Is a chain REALLY only as strong as its weakest link

I heard this quote a lot (especially from my teachers) and I always wanted to know whether or not it was actually true. I think that its partially true; a chain with one weak link is weaker than a ...
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0answers
53 views

What is “W external” and “W internal” in Energy conservation law?

When I solve the energy conservation problem, I am confused when I have to make the term positive or negative. For example, someone throws a ball right up to the ground with velocity, $v$. The ball ...
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0answers
149 views

How strong is the force of space expansion?

There are many questions about space expansion, its cause, or its effects. But I have the feeling we never get straight and simple answers. I do not expect answers to be simple in general, but I ...
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3answers
935 views

The effect of windspeed on a car

I've worked problems in the past in trig class concerning the effect of wind on the speed of a plane and it's flight path and was wondering if a similar thing occurs with a car. First off, I'm ...
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2answers
133 views

Does Centripetal Force Change Direction?

I have been struggling with this question that I have, "Does centripetal force change direction?" From every point, it points to the center. But if we draw its vector, we draw the tails from ...
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1answer
52 views

Modeling wall's behaviour

Sorry if the quesiton is inconvenient, but I judged the physics forum would be the best place to go. My house is divided in two parts by a wall, and there's some tree pushing it, so the wall is about ...
2
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8answers
13k views

Trouble understanding the concept of true and apparent weight

I need help understanding the concept of true weight vs apparent weight. I understand this much: if someone is standing in an elevator on a scale, the further up they go the less the reading on the ...
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2answers
196 views

What will happen in principle if one tries to push a neutron star?

When we push an object it moves due to the mutual repulsion between the electrons in our hand and the electrons in that object. Since a neutron star contains only neutrons, what will happen in ...
3
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2answers
667 views

Loads in decelerating a falling object

I remove trees in confined spaces setting up rigging systems, I am keen to look at the science behind it in more depth so far the formulas that I have found don't take into effect the ongoing effect ...
2
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1answer
1k views

Finding the acceleration given only an angle

This is one of my homework problems for a College Physics I course: Dana has a sports medal suspended by a long ribbon from her rearview mirror. As she accelerates onto the highway, she notices ...
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1answer
132 views

The forces acting on 2 boxes [closed]

Consider the following figure: The surface is not friction-less. When the force $F$ is applied on mass A: Is the force the mass A applies on mass B larger, smaller or equal then the Force that B ...
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1answer
233 views

How to explain centrifugal force from frame of reference of Earth?

Suppose we have a circular table. We have made a straight line groove in the table extending from the center to the circumference. Now we place a block at some distance from the center in the groove ...
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4answers
2k views

If a truck collides with a car, can the truck experience a larger force?

I am confused, here is a question: A large truck and a mini bus both have same velocity V and they collide and stop. The collision lasts for 1 second. A) Which one of the two will experience ...
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0answers
193 views

Why is area considered and not volume to find the force of a solenoid?

I am doing a project involving solenoids. I found multiple websites that say the force (in N) a solenoid exerts on a soft iron bar as it enters the coils can be given by the equation $$F=(NI)^2\mu_0A/...
3
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2answers
170 views

Wasted energy applying a torque

In another question I asked how find a way to deduce wasted energy, but I did not get a satisfactory answer. I have changed the setting here which brings us more close to the solution. Instead of a ...
0
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2answers
471 views

What is a conservative force?

Currently I have three different pictures to describe/understand conservative forces. For the moment I just want to get an electron from point A to point B. In the near surrounding is another electron ...
1
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1answer
998 views

Advanced kinematics problem regarding $F = ma$ [closed]

I really need help with this problem. Thank you for your time. Question: Look at the figure below. Derive the formula for the magnitude of the force F⃗ exerted on the large block (mC) in the ...
5
votes
1answer
241 views

How fast until you feel wind in space? [duplicate]

I couldn't find this question asked anywhere else, so I thought I would ask it here: does anyone know how fast you would have to be traveling in space to feel 'wind' from the particles in front of you?...
3
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2answers
4k views

“Magic” Speed to Drive Over a Speed Bump: Myth or Reality?

A somewhat controversial aspect of speed bumps (sleeping policemen for those in the UK) is that they arguably cause more loss of life than they prevent by acting as a hindrance to emergency response ...
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2answers
37 views

Possiblity of predicting behavior of system when properties described as functions over space?

Suppose I am given a system that consists of a distribution of charged particles(which are all over space and are point-charges). They are described by a set of functions instead of variables. These ...
2
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3answers
3k views

Can you punch a hole in an A4 sheet of paper with your hand?

The heading says it all, but let me explain it a little further. Suppose you hang a sheet of paper (A4 size) from one end leaving the other end free. Now practically it seems impossible to punch a ...
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2answers
6k views

Can a bullet shot through a glass make a clean hole?

One can often see (hopefully only in the movies) that a bullet shot through a pane of window glass leaves a hole in it, but overall the glass is left largely intact. However, a low-speed projectile, e....
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1answer
58 views

Gravitiation force of a sphere

Was wondering about Shell Theorem, specifically about the immediate results. Force (on a point mass) inside a shell is 0. Force (on a point mass) outside a shell is GmM/r^2 From what i know the ...
1
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1answer
851 views

Thrust measured in grams and discerning horizontal acceleration?

So, I have a small ducted fan which has a listed "thrust" of 75 g at a set voltage. I'm going to assume the "g" is short for "grams". Why would this be measured in grams instead of newtons and how ...
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1answer
697 views

Static and kinetic friction [closed]

Say you have block1 on top of block 2 and the whole system is accelerating toward the right at a certain acceleration. Due to inertia block 1 wants to move backward to the left so there has to be a ...
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1answer
77 views

General potential of rotating system

I'm new here at the physics site, and not really that deep into the area of which i'm going to ask a question about now. Therefore please feel free to ask clarifying questions. I'm trying to deal ...
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1answer
56 views

Vectors and Forces problem [closed]

I have a question that I think I have an idea of how to answer but I am unsure can someone please verify for me? Here goes: Here is a box and a force (vector say, F1) of 10 N in the positive ...
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1answer
7k views

Maximum length stretch of vertical spring with a mass? [closed]

Having a vertical spring, if we hang a mass to it, what is the maximum stretch length of spring? and how big should be mass to break the spring?
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1answer
229 views

Electromagnet force equation clarification

So, from a previous previous question, I know what plane the force from an electromagnet will affect a ferromagnetic material in. I thought that would be enough, but working through some problems ...
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2answers
73 views

Diagram of forces exerted on objects

Assuming that there is an interaction between 1 and 3 (they attract each other), what are the forces between 1 and 2? I know it is as if the force acts on a different body (1+2), but I want to know ...
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0answers
58 views

Definition of force in a scalar field theory

How do we define the force for a general scalar field theory? In particular what is the scalar force of the below equation of motion: where $\tilde{T}$ is the energy stress tensor of matter and $A$ ...
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0answers
98 views

Effect of an asymmetric weight distribution on a hack squat machine

In a hack squat machine (see figure above), does it matter if I put more washers on one side? May this asymmetry cause an asymmetry of my effort in performing this exercise? For example, if I put 60.6 ...
5
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5answers
902 views

Forces while squeezing a toothpaste tube

When I squeeze a tube of toothpaste, I am working with 2 squeeze forces toward tube. What causes the toothpaste to go out of the tube? (instead of remaining stationary)
3
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2answers
201 views

Why are some forces not included in the sum of forces?

I was given the following notes in class: 4.32 A skier of mass $65.0\text{ kg}$ is pulled up a snow-covered slope at constant speed by a tow rope that is parallel to the ground. The ground ...
4
votes
2answers
608 views

Why is Buoyant Force $V\rho g$?

For a submerged object, buoyant force ($F_b$) is defined as: $$F_b = V_{\text{submerged}} \times \rho \text{ (density)} \times g \text{ (gravitational constant)}$$ Conceptually, the buoyant force ...
2
votes
2answers
292 views

Reflection - reaction force direction

Let's say an object hits a wall. When the object is reflected does the direction of the reaction force caused on the wall look like the red arrow? Does that direction depend on how "strong" object is ...
3
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2answers
962 views

How to calculate wasted energy

Suppose you are pulling a weight along a track at an angle (in the picture 45°). If the object is dislocated by a distance $D_{45}$ let's assume that the mechanical work done on/energy transmitted to ...
4
votes
2answers
652 views

Acceleration: A ball sliding down the inside of a semicircular bowl

Edit: To clarify, this is a homework question. But I couldn't care less about getting the answer to this specific question as it's not even assigned yet. It looks interesting and I want to understand ...
0
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0answers
170 views

Confusion regarding a method of writing constraint equations

I came across a method for writing the constraint equations known as "The Virtual Work Method".I am quoting the exact language of the text(well,not exactly the exact)- Consider the atwood machine ...
2
votes
1answer
64 views

Why do we exclude the $(i,i)$ case when summing over internal forces?

In the majority of the literature and lectures I see when a system of particles is involved, I usually see the following expression (or similar) for the total force on particle $i$: $$\vec{F}_i = \...
0
votes
1answer
375 views

Determining the force of an explosion, is it external or internal?

A time bomb put inside a box is left into the vacuum: it explodes...the box coverings starts moving I want to ask: is the force behind sudden acceleration internal or external I am confused about ...
2
votes
2answers
6k views

Work done against gravity [closed]

The work done against gravity is $mgh$, well at least that's what my textbook says. I have a question: I can apply a force say 50N, so total work done = $mgh + mah$. Where $ma$ = Force. But the truth ...
1
vote
1answer
1k views

Has NASA confirmed that Roger Shawyer's EmDrive thruster works? [duplicate]

This article states: But somehow, despite all of the reasons it shouldn’t work, it does. Scientists at NASA just confirmed it. Now in this question - it is strongly suggested that this ...
0
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1answer
2k views

Is air resistance affected by both mass and surface area?

If so, which has the biggest impact?
1
vote
1answer
402 views

Question about torque and center of mass [duplicate]

If a yo-yo's string is not attached to anything and the yo-yo is dropped, it is obvious it will fall at $g$. In this scenario, Tension of string = 0. If a yo-yo's string is attached to a cieling and ...
20
votes
5answers
7k views

Is this scene from the A Team explainable by Physics?

This scene (youtube link) from the movie The A-team, the four members are in the tank and its falling from the air, they fire the canon and it slows the tank from falling for a moment before falling ...
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2answers
185 views

Find net force on a mass centered between four other masses

I'm not going to post the full question, I just want a general idea of how I should go about solving this type of problem. There is a square with 4 charged masses on each of the corners, in the ...
0
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1answer
418 views

Don't Inertial forces obey Newton's third law? [duplicate]

I read in a book (Fundamentals of Mechanics by IE Irodov) that inertial forces do not obey newton's third law. I am unable to imagine and get this in my mind. It states: "Inertial forces are not ...