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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0answers
40 views

Viscous force in a conductor

I was told that in a conductor there is a dissipative force and if Ohm's Law is valid for a component, the component has to be dissipative. I'm trying to prove it, but I have some problems. I know ...
0
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0answers
181 views

Does the earth really move round the sun? [duplicate]

Is there really any empirical proof that the earth moves round the sun? I've read simple explanations using mass-gravity relation. But then some questions remain, is gravity a function of mass alone? ...
0
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2answers
130 views

Applying the right-hand rule for magnetic forces

I am confused about the right-hand rule for the Lorentz force. I am using same method as Brightstorm.com is: http://www.youtube.com/watch?v=LK7hv4LX3ys But for some reason it does not match op with ...
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votes
2answers
572 views

Force and Vector question [closed]

A force of 6 Newton and another 8 newton can be applied together to produce the effect of a single force of a) 1 N b) 11 N c) 15 N d) 20 N. More generally, if I know the magnitude of one force, ...
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3answers
290 views

Can you lift a basket up while standing inside it? [closed]

Suppose you stand in a basket and you try to pull the handles of the basket. Will you be able to lift the basket from ground? Similarly, Baron Münchhausen allegedly pulled himself and the horse on ...
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1answer
389 views

Question on static friction [closed]

This is the question, and the answer is given as 2). Now my basic doubt is, are they asking us the direction of the total contact force on the object by the floor? Or, are they asking the direction ...
1
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1answer
622 views

Mechanics question (a block on top of a block) [closed]

This question is very similar to this one here. A block of mass $m_1$ is placed on another block of mass $m_2$ lying on a smooth horizontal surface. The coefficient of friction (static and ...
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1answer
114 views

In Newtonian pressure, what type of function is force?

This is pressure in Newtonian mechanics: $$P=\frac {dF}{dA}.$$ What does this mean? (Doesn't it mean that force is a function of area?) What type of function is force?
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2answers
739 views

Confusion with derivation of fictitious forces

I read the mathematical derivation of fictitious forces on Wikipedia and I'm having trouble understanding it. I went on a few other sites looking for a better derivation, but they're all basically the ...
3
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3answers
3k views

The force arrow for centripetal force points in the opposite direction of my calculation?

I need someone to clarify a conceptual problem I can't seem to surpass. Image there is a rollercoaster loop and a rollerbcoaster car enters the loop at high speed. Once the car completes the full ...
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0answers
1k views

Calculation of magnetic force magnitude from a parmenant magnet

I was wondering how strong a magnet should be in order to be able to horizontally attract 0.2 Kg of pure iron at a distance of 0.3 M. Since I know nothing about magnets, I started looking for ...
0
votes
1answer
5k views

Tension in a massless string around a pulley [closed]

A pulley having some mass has a massless string around it, with two unequal masses at the end of the string. Sufficient friction is present between pulley and the string such that the string does not ...
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4answers
6k views

Why do whips hurt so much?

What exactly is the mechanism that makes a whip deliver such a strong impact? Elasticity, torque, or pressure? Just hitting something with a plank doesn't deal nearly as much damage. What's the ...
1
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1answer
467 views

Calculate magnitude of force acting on some area by falling object

I have simple question: is it possible to calculate magnitude of force acting on some area by falling object? Let's say I have an object with mass $5\text{ kg}$. I drop that object in height 1 ...
1
vote
1answer
466 views

Buoyancy Problem - Cubes in water

I have a tank with water (10 m high) , with an ideal seal at the bottom (water can't fall down, but can enter bodies). I have a system of 6 cubes ( of polystyrene density= 20 Kg/m^3) with dimension ...
3
votes
1answer
358 views

Is there any potential associated with magnetism

Can anybody please tell me if magnetism is a conservative force or if there is a field associated with it? How to reason? One thing I know is that the work done by a magnetic force is $0$.
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2answers
1k views

Is any work done when I walk?

I am trying to figure out the amount of work done when I walk X miles or for X minutes. So I got Work=Force x Distance and Force=Mass x Acceleration and Acceleration=(change in velocity)/time. I am ...
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votes
3answers
852 views

Safest place to sit in the car [closed]

I have to sit in a car which has normal seats in the front, and lounge type chairs at the back, with seatbelts only in the front. The driver drives fast, and I think I may have an accident. So, ...
5
votes
2answers
6k views

Magnetic force doesn't do work and therefore can't change the KE of a particle?

I am having a real hard time understanding the principles behind a question I've come across during test prep. Here is the question: Q: A proton and an electron are traveling in the uniform ...
2
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1answer
188 views

Understanding Kepler's problem

I wanted to know a few things about elliptical motion, that I do not understand so far. Let's imagine that we have an attractive gravitational two body problem where both bodies carry out elliptical ...
0
votes
3answers
2k views

How much torque does it take to turn a doorknob? [closed]

How much torque does it take to turn a doorknob? I'm not looking for an exact answer, just a ballpark for someone who doesn't have a sense of everyday amounts of torque. Here's a very ordinary ...
0
votes
2answers
1k views

force applied not on the center of mass

When applying a force outside of the center of mass of the body, the body will get both linear and angular momentum. Right? Does the linear velocity from this force equal to the linear velocity from ...
1
vote
5answers
547 views

Action Reaction when I pushing a trolley? [duplicate]

I tried to explain how those force work but I can hardly figure it out. I exerted a force on the trolley and there will be a force on trolley on me as well. This is the newton's third law. But why the ...
1
vote
1answer
128 views

Universe with ZERO Fundamental Forces

Warning: I am not a physicist so please excuse my naivety! As you all know, physicists think that there exist four fundamental forces. Would a universe with zero fundamental forces be possible, at ...
2
votes
2answers
555 views

Sum of all forces

Let us glue up these two images, where we get closed loop thrust of water. Force $F_3$ has direction $-x$ and force $F_2$ has $x$ direction. What is the sum of all forces? Can it be more than zero? ...
1
vote
1answer
266 views

A block, a string and Newton's third law

So this is a general force diagram of the system shown. My question is, according to the third law, if the block is exerting a force of magnitude mg on the thread in the down direction, then the ...
2
votes
1answer
94 views

Summing moments, where have I gone wrong?

Because I don't have enough rep to post images, the question is question 3 part iii) from here: http://www.mei.org.uk/files/papers/m209ju_jk32.pdf The surface at the contact point B is rough. The ...
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4answers
1k views

How can acceleration $a$ be zero when applied force $F$ is non-zero?

An object is at rest and stays at rest, but an attached rope pulls with increasing force. What is the acceleration? The correct solution is that acceleration is constant and 0. Obviously $a= dv/dt ...
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votes
1answer
298 views

Question on friction [closed]

Please look at the figure carefully. The question is written, and one has to match the two columns 1 and 2 given under "choices and explanation". Please tell me if I am really wrong, i.e. would you ...
8
votes
3answers
508 views

Where does the extra equation come from to determine the forces from an object on a table?

I have a question about basic statics but somehow I cannot manage to find the answer on my own (btw, this is not a homework. It's been so many years since school for me...). The problem is very ...
1
vote
1answer
390 views

Inclined plane question [closed]

An object, mass $m$ is placed on an incline, angle $\theta$. System is at equilibrium. coefficients of static and kinetic frictions are $\mu_s$ and $\mu_k$ respectively. Then: 1) What is the Total ...
6
votes
1answer
149 views

Why does this screwdriver roll in a curved trajectory?

I am trying my level best to give this screwdriver a horizontal push only, but it is going in a circular path. I thought of uneven friction due to non-uniform normal reaction...what do you think? I ...
2
votes
1answer
192 views

Magnetic Force on a Loop and number of turns

Suppose we have a rectangular current-carrying loop with current $i$, then we know that the magnetic force on each side can be found as: $$F=iL\times B$$ Where $L$ is the vector in the direction of ...
-2
votes
1answer
331 views

A double-sided lever and multiple forces [closed]

Assume a double-sided lever where the left arm has a length of a and the right arm has a length of b + c. Please refer to this ...
0
votes
1answer
228 views

Kinetic energy when $F(t)$ graph is given

The very basic problem here is that the point where this graph ends is ambiguous. I mean, what is the corresponding $y$-value for the point whose $x$-valu is $4.5s$? Then I think we should find the ...
2
votes
2answers
155 views

Intuition contradicting answer for calculating pressure

I have a cylindrical container say of some base area $A$. The atmospheric pressure is $P_0$. The cylinder is moved at an acceleration $a$ horizontally right. I need to find which base would have to ...
1
vote
2answers
489 views

Momentum, Impulse and Newton's Second Law of Motion

Newton formulated his Second Law as such: $$\sum{\vec{F}} = \frac{\delta \vec{p}}{\delta t}$$ and of course, $\vec{p} = m \vec{v}$. Why is it that if the net force $\sum \vec{F}$ is constant (which ...
5
votes
4answers
2k views

How can a car's engine move the car?

Newton's First Law of Motion states that an object at rest or uniform motion tends to stay in that state of motion unless an unbalanced, external force acts on it. Say if I were in a car and I push ...
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votes
1answer
100 views

If An Object Explodes With A Force, What Force Are Fragments Given?

So let's say for example I have an object with 5kg of mass. It explodes with a force of 500N. The object fragments into four fragments: a 0.5kg, a 1kg, a 1.5kg and a 2kg object. What force does ...
0
votes
1answer
173 views

Another Inclined plane question

I did the FBD, and I found too many variables which are not eliminating...Moreover, I believe this question is based on kinetic and static friction. But, $\mu$ here is ambiguously defined...How Do I ...
4
votes
4answers
584 views

Comparing Static Frictions

In this figure, which of the static frictional forces will be more? My aim isn't to solve this particular problem but to learn how is static friction distributed . Since each of the rough-surfaces ...
1
vote
2answers
1k views

Massless string Paradox

If we introduce the notion of a massless string to denote the fact that net force on a massless string will always be $0$, since it is massless . How can these massless strings ever accelerate when ...
1
vote
1answer
89 views

How large of a solar sail would be needed to travel to mars in under a year?

I'm attempting to approach this using the identity $$F/A = I/c$$ I can solve for Area easily enough $$A = F(c/I)$$ and I know the distance $d$ is $$d=1/2(at^2)$$ But I'm having difficulty trying to ...
2
votes
1answer
111 views

Falling through the ground [duplicate]

I do not know much about physics but I know that according to Newtons third law of motion when we walk we are pushing the ground down but the ground is pushing us up. What force is making the ground ...
0
votes
1answer
199 views

Why body starts moving when force is applied? [duplicate]

The recent question by m.buettner regarding self-inductance and its resistance to EMF Faraday's law - does the induced current's magnetic field affect the change in flux?, recalled me the ...
1
vote
0answers
59 views

Does the slinky base stay perfectly level during the initial free fall [duplicate]

In this related question: Slinky base does not immediately fall due to gravity It is observed that the base does not fall immediately. Obviously the center of mass is in free fall, and the tension ...
1
vote
2answers
1k views

Clarification regarding Newton's Third Law of Motion and why movement is possible [duplicate]

Newton's third law states that to every action, there is an equal and opposite reaction. If that's the case, then how do things move at all? Shouldn't all applied forces be canceled by the equal and ...
2
votes
1answer
237 views

Air pressure relative to a force on a bag?

Assume an airtight bag occupied by air such that the pressure inside the bag is equal to the atmospheric pressure. Assume the surface tension of the bag is negligible. What is the change in air ...
2
votes
3answers
806 views

Man in elevator, holding it, on a scale [closed]

This is the scenario where my mass is $60 kg$, the mass of the elevator is $30kg$, and due to a malfunction, I have to hold myself and the elevator at rest. The question is, if there is a weighing ...
2
votes
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 ...