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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2
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3answers
8k views

Rotating a stone with a string

Suppose we are given a stick and a stone tied to the stick by a string. Now if we rotate the stone around the stick the stone rises in height (see picture below). My question is which force accounts ...
4
votes
5answers
360 views

$F=ma$, so if acceleration is zero the force must also be zero?

I was just pushing a huge rock which I couldn't move at all. Given that the acceleration was zero as a result of my efforts, since $F=ma$, doesn't this mean that the force must also have been zero? ...
32
votes
10answers
19k 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 ...
4
votes
1answer
259 views

What are the proposed theoretical explanations for the EmDrive?

The EmDrive is a proposed propulsion mechanism for spacecraft in which some form of microwave device provides the propulsion. The consensus from the physics community, including many voices on this ...
1
vote
1answer
64 views

Maximum angle for highway lane change

I am preparing to fight a traffic ticket from a speed camera. There is a lot more to that story, but the info I need right now involves the angle at which a car can change lanes, in terms of vehicle ...
1
vote
0answers
34 views

Potential (which only depends on the length of a position vector) [closed]

a) A potential $U$ only depends on the length $r=|\vec{r}|$ of the position vector $r$. Show that $$\vec{\nabla}U(r)=U'(r)\frac{\vec{r}}{r}. $$ What properties does this vector field have? ...
0
votes
1answer
36 views

Friction on a body

Consider a cuboidal block kept on a table with friction coefficient $\mu$. When calculating the friction, we use $f= \mu n$ where $n=mg$ for a horizontal table. But a pressure due to the atmosphere ...
4
votes
3answers
861 views

Work = Force x Distance vs Displacement

The difference in using Distance vs Displacement is demonstrated in this example: Work = Force x Distance If I carry an object to and fro 10 metres, the work done would be Force x 20 metres. ...
1
vote
2answers
96 views

In which direction does mud fly off a moving bike's tire & why?

If a bike moves through a muddy area, mud gets on its tires. Then the mud flies off from the tires. Which forces are acting on it? In which direction does it fly off? On my physics test, I wrote ...
-1
votes
1answer
28 views

How would change force of gravity? [closed]

How would change force of gravity, impacting some object, when this object is lifted on height $h = 3 \cdot R_3$. The right answer stated as ("decrease 16 times"). I want to know why.
1
vote
1answer
11 views

Is the index of time in the unit equivalent to force dependent on the number of dimensions

When the unit of force is represented as $\text{distance per time}^n$ in 3 dimensions $n$ is equal to 2. Is n also equal to 2 for higher or lower dimensions (2D, 4D, 5D, ...) or is it dependent on the ...
0
votes
3answers
88 views

Question on normal force and static friction [closed]

Why is this statement false: If the normal force on an object increases, the static friction must increase? Thank you! Is it because they did not state what normal force is referring to?
2
votes
3answers
446 views

Why do non-accelerating objects exert force on each other?

The equation for force is $\vec{F} = m\vec{a}$, where $\vec{a}$ is acceleration. Acceleration is a change in velocity. However, if an object with constant velocity (i.e. 0 acceleration) hits another ...
0
votes
0answers
15 views

How this tube rotates? [duplicate]

I recently seen a video where a tube is spin into space. When it starts to rotate, it keeps continuously to rotate along the axis of 180 degrees clockwise, then 180 counter-clockwise and so on. The ...
2
votes
4answers
412 views

What causes a car's velocity to follow the front wheels' direction?

I'm trying to simulate a car with correct physics models. In this example we let the car have a constant speed, and there are no forces (friction and drag) to slow down the speed. Here's a video that ...
0
votes
2answers
56 views

simple force question

So given this diagram, I was supposed to find the magnitude and direction of the net force on the -10nC charge on the bottom right corner. I found the magnitude by myself using Coulomb's law for the ...
1
vote
1answer
53 views

How does one calculate or even approximate the force observed by a magnet as its dropped inside of a diamagnetic cylinder?

How does one calculate or even approximate the force observed by a magnet as its dropped inside of a diamagnetic cylinder? Wikipedia and Google does not provide much information on this topic. ...
0
votes
1answer
72 views

Do we all actually just weigh half of what our bathroom scales tell us?

Here's the reasoning: Newton's third law tells us that every force has an equal but opposite reaction force. So besides my weight pushing down on the scale from above, there's also an equal force ...
0
votes
2answers
87 views

Gravitational force in a building

Suppose that a person is standing on the top of a multi storey building and at an instant earth's gravitational pull becomes zero.What will happen in the next instant? (Consider only earth's gravity ...
2
votes
2answers
86 views

Mathematical Proof of Force

I remembered reading an paper a while ago which tried to prove whether force actually exists, or if it a man made construct to aid our understanding of the world. However, I can't seem to find the ...
0
votes
1answer
51 views

Coefficient of elasticity of the spring?

I know this might sound a silly question though For a spring that is compressed lets say x meters by a force F N. what is coefficient of elasticity of the spring? We are not given the equilibrium ...
0
votes
2answers
67 views

Can we make a force which can oppose earth gravity? [duplicate]

IF We are standing on a earth.then some force (gravity of earth) is pulling us down..then "cant we make a force which can oppose gravity..? Cant we make a object of zero mass..?
1
vote
2answers
47 views

frictional force is nonconservative force [duplicate]

In nature there are mainly four kind of fundamental forces,electromagnetic force is one of them which is conservative force.If friction force is belongs to electromagnetic force then why it is not ...
1
vote
1answer
25 views

Half of a uniform disc suspended by two strings [closed]

Suppose we have a half of a thin, homogenous disc hanging from the ceiling as shown: Given the weight of the disc $Q$, calculate tensions in strings $S_1$,$S_2$. Now this seemed like quite a simple ...
2
votes
3answers
200 views

Weight distributions [duplicate]

If a man is standing on two weighing machines (scales), with one foot on each, Will both machines show equal weight or his weight will be distributed in two machines?
2
votes
0answers
56 views

Force required to crop/cut a mild steel bar [closed]

I have cropping wedges with a diameter of 4mm cutting either side of a round mild steel bar (17.5mm). These wedges are operated using 2 hydraulic cylinders (6" diameter, 2 1/2 travel) (one for each ...
0
votes
1answer
214 views

Maximum range of projectile launched from an inclined plane [closed]

As we already know the max range if we launch it from any flat surface or from any height but I was wondering what will be maximum range if we launch it from inclined plane. I have made on figure of ...
0
votes
0answers
20 views

How is the strength of a force quantitatively evaluated?

Physicists often talk about the 'strength' of a force. For example, gravity is weak, the strong force is of course strong. The hierarchy is summarized on this wikipedia page, which lists strengths in ...
1
vote
2answers
107 views

Why do we feel resistance to gravity rather than the acceleration of gravity?

What's the reason it behaves differently from all other forces? What I mean is, if you're in orbit you're accelerating toward the earth at almost 9.8m/s^2, but you feel nothing. If you are riding a ...
0
votes
1answer
58 views

Force in a moving object that is not accelerating

If an object is traveling in a straight direction at a constant speed it has no acceleration, right? So if $F=ma$ and $a =0$ then force should equal 0. Does that mean a car traveling at a constant ...
2
votes
2answers
67 views

Does friction act on a wheel rolling at a constant speed

One of the things I've seemed to have taken for granted is that its the friction the floor exerts on a rolling wheel that prevents slip from occurring. However, I ran into something that challenges ...
0
votes
1answer
35 views

What does “interact via strong force” mean?

I was just wondering if the words "strong force" and "strong interaction" are interchangeable? Also, these are referring to "strong nuclear force", correct? Then what does it mean for particles to ...
0
votes
1answer
57 views

Force Needed To Maintain Velocity, Increasing Mass

Hoping somebody could give me a hand with this. Unfortunately I haven't taken physics yet, my background is in math/computer science. I'm studying computational science and the problem is essentially ...
4
votes
4answers
8k views

Does a car use friction to move?

When a car's engine injects fuel into the cylinder chambers, the reaction creates a force that generates rotational momentum to the shaft and over the transmission, it translates that power to the ...
2
votes
2answers
1k views

Countersteering a motorcycle

Everyone knows the story about countersteering. For those who don't I will explain it below and after the explanation i will ask my question. You can watch this short video as a beginning: ...
2
votes
3answers
845 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 ...
0
votes
0answers
16 views

The contact pressure on a solid surface by a rod connected to a solid piston?

Below I have two pictures, one of which is single piston (blue) made of a solid material inside of a chamber (black) and the rod (magenta) is in contact with a rigid surface (teal). The second picture ...
2
votes
2answers
32 views

Formula for balance with three arms?

I'm searching for a way to express the angle of the arm of a balance instrument expressed in the weight that is present in one arm. For a two legged balance one could use the moment formula: moment = ...
3
votes
3answers
645 views

Does a heavy body move with the slightest force on a frictionless surface?

If I apply horizontal force on a body resting on the ground, my force will be opposed by the frictional force and the body will accelerate at the point where my force exceeds the force of friction = ...
3
votes
3answers
100 views

Force Body Diagrams of object sliding down ramp

So I think I am confusing myself about forces. I know that when something is sliding down a ramp that it will have the force of gravity, normal force and force of friction acting on it. But for an ...
0
votes
1answer
29 views

Buoyant force on a certain object

Sometimes a certain body is completely immersed in water, but it does not sink deeply, it is stuck in the middle... In this case, is the buoyant force equal to the weight of the body? Why?
4
votes
3answers
224 views

Can we rigorously define force?

I'm looking to get rigorous definitions on which to base the important quantities in classical mechanics. To me a "rigorous" physical definition is an operational definition -- that is one in which ...
0
votes
1answer
37 views

Is force exerted by Earth different for different mass?

We know Earth pulls every object by the same acceleration $g$ (say). force exerted by earth $F=m\cdot g$ (with $m$ the mass of the body), so, if $g$ is constant then $F$ is directly proportional to ...
1
vote
1answer
40 views

Definition of Force Using Momentum

When we use F = change in momentum / change in time, is that the average force applied? There could be different magnitudes of force applied over time to change the momentum (it could be instantaneous ...
0
votes
1answer
38 views

Pressure and force of ideal gas in a leaking container?

Let's imagine you have a container that has a pressure of 10 Pascals inside and a vacuum outside. The container has a volume of a cubic meter and I'm not sure if the temperature matters but lets say ...
0
votes
0answers
51 views

Is the acceleration of a soap bubble the standard value of gravitational acceleration?

Is the acceleration of a basic soap bubble the same as the standard value of gravitational acceleration 9.81 m/s^2 when it is dropping in a windless space? I have used the Newton's 2nd law to prove ...
0
votes
0answers
34 views

Forces acting when we squeeze a ball?

I have few doubts to clear. I would like to know the forces acting when we squeeze a foam ball. Mode of squeeze will be by placing the ball between the palm of the hand and the four fingers. What ...
9
votes
2answers
169 views

Can the coefficient of friction be derived from fundamentals?

It is common to want to derive macroscopic laws from what we know microscopically - after all, given a (correct) microscopic description, everything larger should follow. Has it ever been done to ...
1
vote
1answer
37 views

A Question on Friction [closed]

And yes, this is not a homework thing.Here's my working.
1
vote
3answers
155 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. In Goldstein d'Alembert's principle is given as: $(F-\dot{p}) \cdot \delta r = ...