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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3answers
2k 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 ...
1
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0answers
26 views

Kinetic Damping Behavior [closed]

For a problem I am given a block attached to a spring attached to a wall with mass m and coefficient of friction u. The magnitude when it is sliding is friction=$mgu$ opposite motion. It won't move ...
6
votes
2answers
5k 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, ...
0
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1answer
57 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
696 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 ...
1
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0answers
1k views

Tension Problem: Solve for T for two sliding blocks connected by a string [closed]

The problem: Two blocks made of different materials connected together by a thin cord, slide down a plane ramp inclined at an angle θ to the horizontal as shown in the figure (block B is above ...
2
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1answer
671 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 ...
1
vote
1answer
73 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 ...
-1
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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 ...
0
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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?
1
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1answer
215 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 ...
1
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2answers
72 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 ...
0
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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 $A$ ...
0
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0answers
92 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 ...
5
votes
5answers
799 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
votes
2answers
192 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
532 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
261 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
votes
2answers
903 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
616 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
votes
0answers
152 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
63 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
326 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
5k 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
votes
1answer
2k views

Is air resistance affected by both mass and surface area?

If so, which has the biggest impact?
1
vote
1answer
379 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
6k 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 ...
0
votes
2answers
175 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
votes
1answer
396 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 ...
-4
votes
1answer
152 views

About how much force would something have to exert to be effectively unstoppable? [closed]

Assuming an object is moving in a straight line propelled by a force. How much energy would that force have to exert so that there are no known forces or objects that could stop it from moving in that ...
0
votes
2answers
2k views

How did tension developed in a string when two equal and opposite forces are applied on the same body?

As per Newton's 3rd law every action has an equal and opposite reaction, but both of these forces are on different bodies under consideration Now when a single body (say rope in this case) is ...
2
votes
1answer
134 views

Tension in a chain around a cone

A chain of some mass, forming a circle, is slipped on a smooth cone. If we consider an infinitesimally small section of the chain, a component of gravity will try to accelerate it along the surface of ...
3
votes
1answer
492 views

How is weight distributed when legs are astride?

Is there a simple and quick formula to find the weight (the force acting) on each leg, especially when legs are astride and they are not equally stretched? (or, better) not equally distant from the ...
0
votes
1answer
6k views

Why does the co-efficent of kinetic friction of a block on an inclined plane not change when you increase the angle of the plane?

The coefficient of kinetic friction can be calculated using $\mu_k = F_k/F_n$. A change in angle does not affect the normal force, but doesn't a change in angle affect the friction? As in if the angle ...
2
votes
1answer
84 views

How is dark matter meant to explain the faster than expected rotation of galaxies? [duplicate]

The stars on the outer edges of galaxies go around faster than they should be. How is dark matter meant to account for this? if you just add more mass wont that just give it a greater gravitational ...
2
votes
1answer
303 views

Calculate direction vector given start-end positions and velocity?

I'm trying for a week now and I really have a hard time with this one. I'm pretty sure that this is something very simple but I can't seem to find a solution. I'm making a game where the enemy is ...
3
votes
3answers
593 views

Electric force between charges in two different media

As far as I know, Coulomb's law of electrostatic force is applicable on two different charges situated in same medium. But if two individual charges are in different media (say one charge on a iron ...
0
votes
1answer
65 views

Finding directions of the internal forces within a freely jointed rigid object?

Consider the the following problem: Here is a force diagram showing the situation: For part (i) Taking moments about $B$ for $BC$ gives $84.5Lcos\beta=2LT$ So $T=39$N For part (ii) Resolving ...
0
votes
3answers
496 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 ...
1
vote
1answer
5k views

Derivation of formula of potential energy by a conservative force [duplicate]

the formula for potential energy by a conservative force is given by: $$ F = -\nabla U(r), $$ which in one dimension may be simplified to: $$ F = -\frac{dU}{dx} .$$ My question is how is it ...
4
votes
2answers
84 views

Determining average number of fragments created upon explosion

Suppose you're analyzing some 3 dimensional object of any sort of shape, and this object explodes from some internal force (e.g, like a grenade). How would you go about determining the average number ...
19
votes
7answers
7k views

The best way in which a man can pull a train

I have chosen this example as a paradoxical limit, but my question really regards the optimization, distribution and outcome of force when you try to pull a weight: how can you optimize your ...
0
votes
2answers
261 views

Calories Burned While Hiking [closed]

I want to find out how many calories are burned on any particular hike by any particular by using a formula. I figure it's probably a simple physics question, but since I never took physics, I don't ...
1
vote
2answers
53 views

Force on every particle?

Say there is a horizontal rod, where a force $P$ is applied to the right hand side of the rod to drag it horizontally to the right. If I drew a force diagram, I'd put some vector with a length of $\| ...
0
votes
1answer
2k views

Calculating Resultant Force and Torque

I'm working on a sandbox game that allows the player to build a spacecraft and attach thrusters in arbitrary locations on the hull of the spacecraft. The game is set completely in 2D. (I'm a ...
0
votes
2answers
412 views

Why doesn't a car slide down a banked road when there is no friction?

In case of banked roads without friction, there is an additional $mg \sin(\theta)$ which is unbalanced. Why isn't this taken into account because it is responsible for making the vehicle slide down ...
1
vote
1answer
691 views

Forces acting on a double pulley

In a double pulley system, if the mass of the object is 10 kg and the object is accelerating upwards at 2 m/s$^2$, what is the tension in the ropes? I figured the weight of the box is 100N and the ...
5
votes
5answers
2k views

Will gravity pull together two bodies from the other side of an empty universe?

Lets say that there are only two bodies in the universe, 65 kg each. Other than that the universe is completely empty, no neutrons, no photons, no dark energy/matter, not even neutrinos (that is to ...
1
vote
1answer
171 views

Pseudoforce and friction: confusion

Consider the following situation. A block of mass $M$ is resting on a rough horizontal ground, and a frame is moving towards the right horizontally with an acceleration $a$. Suppose the coefficient of ...