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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32 views

Applied forces on a bridge [closed]

What are the forces that acted on the 6 types of bridges? Beam, Truss, Cantilever, Arch, Suspension, and Cable-Stay? What formulas do you use to get the forces? I'm curious since there is ...
1
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0answers
25 views

How can a net force of 0 still lead to movement and how is movement possible with interaction pairs? [duplicate]

So I always thought of movement as interaction pairs. For example, I thought that a rocket moves by applying a force of hot exhaust gases, which then apply a reaction force back on the rocket ...
3
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2answers
71 views

Understanding Density and the Buoyant Force

A beaker of water resting on a scale registers a weight of 0.61 N. Lowering a steel cube completely into the water (without making any contact with the beaker) causes the reading on the scale to ...
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3answers
66 views

Violation of Newton's third law

consider the following situation shown in the diagram below.A huge wall of mass M is moving to the left due to a constant force of 100N. Now suppose a man of mass m applies a force of 20N to the ...
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1answer
67 views

Max Acceleration on an incline? (2010 F=ma #8) [closed]

(From 2010 F=ma, #8) A car attempts to accelerate up a hill at an angle θ to the horizontal. The coefficient of static friction between the tires and the hill is µ > tan θ. What is the maximum ...
2
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2answers
80 views

how does one divide stress in such a bridge? [closed]

I want to build a spaghetti bridge like this: I have two spaghetti types: T-type (designed to tolerate tension) and C-type (designed to tolerate compression). A mass $m$ is hanging from the point ...
3
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0answers
57 views

How is Temperature and Pressure related to when a tire rolls on the ground?

Actual observation: Here in Canada it is known that even when 'dry' snow is on the ground, and when a car drives over it that small amount of dry snow instantly becomes ice (NOT GOOD). Anyways as an ...
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1answer
39 views

Force (torque) to break a bike handlebar? [closed]

Few weeks ago a neighbor manage to hit my bike with his car while the bike was parked next to a wall, check the picture. One side of the handlebar was at the wall and the door of his truck hit ...
2
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1answer
44 views

Is the integral of $dK$ equal the work done?

$$\frac{dK}{dt} = \frac{d}{dt} (1/2 mv^2) = mv \frac{dv}{dt} = F\frac{dx}{dt}$$ $$\implies dK = F. dr$$ Also, work is defined as $W = \int F. dr$. So does this imply integral $dK = W$?
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4answers
59 views

Buoyant force in an elevator

I can't understand why buoyant force exerted by the liquid on a ball attached to a rope in a box having liquid of density $p$ moving in an elevator moving with acceleration $a$ has buoyant force as, ...
0
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2answers
42 views

Does it take a larger force to stop a faster object?

Does it take a larger force to stop a car that is moving at a velocity 2*v than if it is moving at a velocity v? I'm confused as the force required to decelerate a car depends on the mass and the ...
2
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1answer
53 views

Pascal's law and pressure gradient

Pascal's law states that pressure applied on an ideal liquid is equally distributed. Then why is there a pressure gradient in a liquid body? Please let me know what is wrong in what I stated. What ...
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1answer
30 views

can a single force rotate an object. not a torque

Can a single force (not a torque) rotate an object? How can the bar below fall given the force $\mathbf F$?
0
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2answers
97 views

Why are gravity and spring-force conservative forces?

I know that the amount of work does not depend on the followed path but on the position when speaking about conservative forces. But could someone please prove/explain why exactly those two are ...
1
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1answer
27 views

How far will the key slide? [closed]

A person tosses his car keys on a shelf with an initial velocity of $2\:\mathrm{m/s}$. How far will the keys slide if the coefficient of kinetic friction between the surfaces is $0.3$? How would you ...
0
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3answers
57 views

When walking, why the foot which get the reaction doesn't accelerate?

To walk we apply a force and the earth gives us a reaction. But the foot which get the force doesn't accelerate.
0
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3answers
74 views

Why can't we define a potential energy for a non-conservative force? [closed]

We could define potential energies for non-conservative forces too and then we could conserve it with kinetic and potential energy as we know it. But no one does that. Why is this? Please explain. Any ...
2
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3answers
34 views

What is the gravitational pull if one has as much mass above them as below them? [duplicate]

I understand the previous responses to other answering if you were at the center of a planet, would you be weightless? Yes you would due to the forces of gravity pulling at you from all sides. ...
0
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2answers
24 views

Confusion regarding resolution of forces

I'm looking at a basic free body diagram of a car travelling on a banked(inclined) road with inclination theta. It's mass is 'm'. Here the diagram shows weight (mg), Normal reaction(N), and ...
0
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1answer
74 views

What is the speed of magnetism?

I'm not a physicist (just have a few basic notions) and this is a question out of curiosity, so as I'll probably word it the simplest I can, please take that into account when answering. tl;dr Let's ...
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2answers
41 views

Horizontal net force question [closed]

A 1580kg car travels at 15m/s, what would the magnitude of the horizontal net force required to bring the car to a halt in 50m?
0
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1answer
108 views

Can Newton's 3rd Law be considered as a direct consequence of the coulomb's law of electric interactions? [closed]

Let me explain my thought. Lets consider Coulomb's definition of electric force between two charges as the fundamental law. Under this consideration, forces between charges already follow What ...
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2answers
40 views

Equilibrium on a fixed wedge

While solving a question I came acrross this doubt.For a block in equilibrium on an inclined wedge, the summation of forces should be equal to zero.I am confused because I got two different results ...
0
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2answers
77 views

Does a man run a same distance with different velocities spend the similar energy?

To simplify the question we assume the same man run on a straight and flat road with constant speed. Personally I don't believe the man would spend a similar energy. But how to prove it in physics? I ...
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0answers
20 views

Point charge inside a electrically neutral cavity in conductor placed eccentrically, and effect of external electric field if switched on

bear with me, but i would like a definite answer, now, starting off the external charge density on the outer surface of sphere WILL be uniform by unique solution of Laplace equation and letting the ...
4
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3answers
397 views

What does it mean to say work is path-independent when pushing an object in different directions?

If I apply a straight upward(perpendicular to ground) force against gravity of $5\ \mathrm{N}$ and lift an object "A" 10 meters, then the work done is: $$ W = F \times S = 5\ \mathrm{N} \times 10\ ...
0
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1answer
43 views

Why there is an extra componet of force in this Equilibrium state?

I have a question about the forces on a body at equilibrium. Look to this image: here i draw a man standing with a pen on earth. And I think that I draw all possible forces on it. They are as ...
0
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2answers
39 views

In a vacuum, given two identical objects, if one is stationary, what would happen if the two objects collide?

Given these two identical objects, if one is stationary, and the centre of mass of the other object collides head on with the centre of mass of the object that is stationary, i.e it does not come into ...
0
votes
1answer
47 views

How are unbalanced forces even possible, given Newton's 3rd law? [duplicate]

The notion of an unbalanced force seems to contradict Newton's third law, entirely. For instance, apparently, if you push a rock, then an unequal force is being applied in the opposite direction with ...
0
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0answers
11 views

Stick stands in the corner then starts to fall, when will it detach from the wall? [duplicate]

A thin homogeneous stick stands on the smooth(no friction) floor, leaning against a smooth wall,stands absolutely vertically. (Imagine a corner).Then it starts to fall(with zero initial velocity).What ...
1
vote
1answer
89 views

Are pull ups as performed by Oliver Queen in the TV series The Arrow possible?

Referring to the pull ups performed by Oliver Queen in the TV series The Arrow. My hunch is that such pull ups are impossible because it violates the law of physics: as Oliver tries to pull himself ...
1
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0answers
50 views

Pulley system on a double inclined plane [closed]

(Lets say, say static friction is $\mu_s$, and kinetic friction is $\mu_k$ for both of them) What is the detailed definition of static friction according to this picture? When the system starts to ...
3
votes
3answers
57 views

Why does a teeter-totter (see-saw) tend to incline towards the heavier end?

Why does a teeter-totter (see-saw) tend to incline towards the heavier end? Since objects of different mass tend to fall at the same speed (assuming a vacuum), why do then heavier objects push harder ...
2
votes
1answer
85 views

Understanding rocket equations [closed]

I'm doing a science project where I have to explain the physics behind a trip to an exoplanet and I also have to explain about rocket equations while doing so. I know that a trip to an exoplanet is ...
1
vote
1answer
37 views

Experiment to show $a \propto F$

I learnt about an experiment to show that acceleration is proportional to force. It was done by placing a trolley (like a toy car) on a smooth track. At the end of the smooth horizontal track was a ...
0
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1answer
46 views

Inclined plane problem [closed]

This is the problem question from my textbook. My questions are concerning some formulas related to this problem. The force of friction is obviously down the plane. My initial question is: ...
0
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1answer
62 views

Newton's 3rd law applied to friction

I'm confused about how Newton's 3rd law applies to friction. If you slid an object across a table then the particles you are sliding against would exert the same force back, but wouldn`t this mean ...
0
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1answer
81 views

Why doesn't gravity have charges?

All other forces have some kind of charge system, electromagnetism has positive and negative, weak force has hypercharges, and strong force has colors. Why doesn't gravity have anything like these?
0
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1answer
120 views

F=ma is true in an accelerating coordinate system [closed]

There are plenty of similar topics about the physical or intuitive meaning of the equivalence principle or statement such as ''laws of physics are true in every frame of reference''. Usually answers ...
1
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0answers
19 views

Accelerated flow [closed]

Consider the following two cases: 1. Flow past a body, which is in constant acceleration and 2. Constantly accelerated flow over the body when it is fixed. Will the forces experienced by body in both ...
0
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1answer
43 views

Will loss of contact with the ground remove friction forces?

If we suppose that one object is losing contact from the floor, let's say the trajectory of this object is a semisphere, then in this instantaneous time just before the contact is loss will make the ...
1
vote
2answers
66 views

If an object has a constant force being applied to it perpendicular to gravity, will the object fall slower?

If this was on a hypothetical flat plane (so not curved like the earth) and a rocket is flying horizontally, would the horizontal propulsion slow down the rocket's descent or even stop it from falling ...
0
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2answers
39 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
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0answers
59 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
votes
1answer
64 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
votes
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
63 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
62 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 ...