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
40 views

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 ...
4
votes
0answers
60 views

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 ...
0
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1answer
66 views

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 ...
-1
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1answer
55 views

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 ...
14
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4answers
222 views

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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2answers
67 views

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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1answer
130 views

Is this picture of relativity correct? [closed]

Can forces be said to exist in a real sense in general relativity?
1
vote
1answer
63 views

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 ...
1
vote
4answers
80 views

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 ...
12
votes
5answers
3k views

Is there any friction between wheel and road?

Human beings invented the wheel to get rid of the friction between the wheel and the road. But were we able to reduce it to zero? Is there any residual friction? This question is about only the ...
0
votes
1answer
49 views

Rate of applied force versus material failure?

Question: Does the rate at which a force is applied to an object determine the maximum force reached that mechanically fails the object? If so, what are the concepts that need to be understood to ...
1
vote
2answers
57 views

Is it feasible to lift a human off the ground with a suit of fans? [closed]

So, we live in a world that is technologically developed enough where it is reasonably within reach to attach small rockets to someone/something to lift it off the ground. One serious problem we ...
0
votes
2answers
34 views

Tension at topmost point of a vertical circle

I read that for a body to move in a vertical circle, the minimum tension needed is 0 at the topmost point. Can someone explain to me what it means to have positive or negative tension on top. I'm not ...
0
votes
2answers
58 views

Levitation using Electromagnets - Forces

Here is a hypothetical (but potential real) situation: I am holding electromagnet that weights 1kg. This electromagnet is being used to hold up a 10kg weight. Would I feel like I am holding 11kg, or ...
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votes
1answer
51 views

Is there a way to study mechanics without having to rely on free body diagrams?

For example, consider a very simple situation often used as example in teaching: a horse pulling a stone through a rope attaching them. The analysis goes something like this: There is a force ...
0
votes
1answer
63 views

How does a pop pop boat work?

I have been reading about the pop pop boat on wikipedea. What I don't understand is after the hot water is ejected the vacuume gets created, so when the same amount of water will be sucked in the boat ...
2
votes
4answers
308 views

Better explanation of why an object floats: density? or buoyancy in equilibrium with object's weight?

Across StackExchange, you see two explanations for why an object floats: The buoyant force, equal to weight of displaced water, is in equilibrium with the object's weight. The density of the object ...
0
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0answers
27 views

Integral of Forces is the Velocity

I am self learning classical mechanics. I have the following problem: At time $t$ we have a force $f(t)$ acting on a particle with mass $m$ that is at distance $x(t)$ from $0$. We also assume ...
0
votes
1answer
66 views

Gravity: Why Do things fall to Earth? [duplicate]

If gravity is in reality spacetime geometry why when I drop an object on the surface of the Earth does it fall to the ground? Does spacetime push it?
0
votes
0answers
44 views

An object on a conveyor belt

Let's say a bag (30kg) is sitting on a moving conveyor belt and at the end of the conveyor belt, there is a wall. Since the belt is moving at a constant speed (say 2.0 m/s), when the bag hits the ...
0
votes
0answers
18 views

Finding impact force of a railroad car?

I'm in the process of writing a software that can best be described as a modified train simulator (if you're into model railroading you might like it, see here) and I need to simulate coupler slack ...
2
votes
3answers
85 views

Estimating Squeezing Force of Toothpaste Tube

How could I estimate the force I apply when I squeeze a new toothpaste tube? I want to either be able to calculate it without having to perform an experiment, or refer to some scientific journal with ...
0
votes
1answer
45 views

Force Exerted on a Rocket

I am reading Spivak's "Physics for Mathematicians". He has the following setup up: We let $m(t)$ be the mass of a rocket and its fuel at time $t$. And, we let $q(t)$ be the velocity at which the ...
1
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0answers
50 views

Are there any universal forces which are cartesian in nature? [closed]

I was recently talking with someone about how I think the whole Cartesian xyz understanding of the universe evolved from animals thinking earth was flat. They could get along fine without having to ...
1
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2answers
190 views

Elongation in bar with unequal applied forces

How is elongation in a uniform rod with unequal forces acting on opposite sides calculated? If applied forces are equal and opposite, the elongation is defined by the formula ($\delta = ...
0
votes
2answers
37 views

What would all the forces on a space elevator be as it moves up and down?

At the bottom, the acceleration due to gravity would be g. At the top, it would be something like .8g... But would the total acceleration effectively be 0 like on the ISS? How would the acceleration ...
0
votes
1answer
30 views

Compression of a gas in a cylinder

On my test I had a question: A movable, friction-less, and rigid piston stands upright with a 10 kg weight resting on top like this, compressing the gas inside. If the piston is turned on its side, ...
1
vote
1answer
40 views

What is meant by the word “length” in definition of surface tension?

Surface tension is defined as the force applied per unit length. What is that "length" belonging to? I can imagine force being applied per area but not length. "It would take a force of 72 dynes to ...
1
vote
2answers
34 views

In terms of forces and kinematics, why does a projectile, thrown forwards, bounce forwards?

I'm curious to know why a tennis ball bounces forwards after it has made contact with the ground considering I throw it forwards and downwards at the ground. I understand that is bounces up because ...
0
votes
2answers
28 views

Nature of Pressure

Pressure is defined as force per unit area. Therefore, pressure = force divided by area. Since force and area are both vectors, how can we perform this division without violating the rule of vectors? ...
3
votes
2answers
96 views

What happens when two bodies collide in a dynamics point of view?

I'm a high school student learning about energy and momentum. What confuses me is the things with elastic and inelastic collisions. I completely (in my opinion) understand those concepts in energy ...
0
votes
0answers
50 views

Can quantum mechanics, general relativity and all physical theories be reduced to geometry? [duplicate]

I was told by my, perhaps ignorant (that is for you to decide), teacher that "all physical theories can be reduced to geometry in the manner of Newton's Principia/Euclid's Elements, however, due to ...
-1
votes
2answers
96 views

Work done by Friction. Can it be positive or zero?

The work done by frictional force is negative as it opposes the relative motion? Please explain when will the work done by friction be (i) zero (ii) positive ?
0
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2answers
69 views

Few questions related to Tension

I am struggling with the concept of tension in a rope. Below specific questions. I am understanding tension to be an elastic force between rope molecules. If so, is it fair to say the net tension ...
0
votes
2answers
52 views

Acceleration due to gravitational force [duplicate]

I need some help with below. So according to Newton's 2nd law, $a=F/m$, for a given mass, the acceleration depends on mass. But acceleration due to gravity is independent of mass. There seems some ...
1
vote
0answers
73 views

Will the block #3 move? [closed]

Hey, On my test I've been assigned to calculate acceleration of the box with mass = m3(I'll call it block #3). The problem is, I can't even imagine the block moving, as I cannot find any force ...
1
vote
0answers
21 views

Am I exerting force when i am holding something? [duplicate]

So theoretically I found out that I am NOT exerting any force while I am holding something! Like Sir Isaac Newton said F=ma So technically it is true that when I hold something I am resisting it's ...
0
votes
2answers
45 views

Does force get divided among things?

If I exert a force to more than one thing at a time, will the force be divided among them or all of them will feel the same force? I mean imagine that I have tied up 3 bags of same mass with A rope ...
0
votes
1answer
77 views

How to prove that “all unaccelerated frames behave likely for all isolated bodies”? [closed]

Say in an unaccelerated frame "S" a "isolated body A" moves with constancy of velocity , can we predict mathematically that any other such body B will move with same velocity in that frame.... My ...
1
vote
3answers
173 views

When does normal force equal to $mg$?

Can someone once and for all explain when does normal force equal to mg? I know for sure that when there is no friction, normal force will be equal to mg. But, i encountered some questions when there ...
1
vote
2answers
40 views

Friction in driving car

We know friction helps in driving car, does this mean car can move faster on rough surfaces ? Since coefficient of friction is more on rough surfaces
1
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2answers
100 views

Best angle to pull an object

I'm fairly new to physics (high school) but really enjoy. I recently came across a problem of my own that I tried to solve: what is the best angle to pull an object at? I derived $F=F\cos \theta-\mu ...
1
vote
1answer
61 views

Looking for a specific theory concerning Dark Matter [closed]

I am looking for the name of a theory positing that "empty" space itself is not empty, but has substance, and that "fabric" or "substance" is actually what we call Dark Matter. In theory, dark matter ...
2
votes
2answers
150 views

Is the reaction force for a stone hitting a wall infinite?

Let us assume a rigid stone which moves in empty space with a constant speed of $v$. (Or in the air with no friction and drag or you can imagine a free fall with friction). This stone hits a rigid ...
0
votes
2answers
44 views

Is Buoyant force a reaction?

When we fall on water. The surface molecules are pushed down and as a consequence molecules below the surface molecules and molecules beneath them and so on are also pushed down. Some of them are ...
0
votes
1answer
52 views

Is there any way to create a globe with gravitational or similar attractive force - earth simulator?

This may sound like a dumb question. Is there anyway to create a miniature version of earth or its gravitational force. A globe or sphere which have force inside it which can attract the things ...
13
votes
4answers
860 views

The maximum distance for which Coulomb's law has been verified?

We know that Coulomb's law, $F_{12} = \frac{kq_1q_2}{r^2}$, was experimentally verified for small distances by Coulomb himself at the and of the XVIII century. The question is what is the maximum ...
0
votes
2answers
51 views

Finding Friction and Coefficient of Friction Force? [closed]

A $65\,\mathrm{kg}$ object slides down a $30^\circ$ slope at a constant speed. Air resistance is negligible. Find the coefficient of friction and force of friction. The normal force equals ...
0
votes
2answers
45 views

Why do riders feel forced down into their seats at the bottom of the first drop on a rollercoaster?

I am trying to figure out what forces an $80.0kg$ rider travelling at $110.0km/h$ ($30.56m/s$) would experience when at the bottom of the first drop on a rollercoaster where the radius of the ...
4
votes
2answers
98 views

How can photons cause charges to attract? [duplicate]

Photons are the force carrier of the electromagnetic force. I do not see how this could result in a transfer of momentum that attracts objects together. I am primarily interested in an intuitive ...