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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1answer
79 views

Force-carrying particles instead of forces

Are there physical theories in which notions of particle are used without the concept of force? I know about gauge bosons, see: http://en.wikipedia.org/wiki/Force_carrier and ...
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1answer
42 views

two bodies are travelling with equal acceleration

two bodies are travelling with equal acceleration in the same direction and are in contact with each other. What will the force exerted by 1st body on second be? By taking an example of masses 5 and ...
2
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3answers
436 views

What do tensile strength values mean and why are they reported in units of pressure?

How does one interpret the numbers when reading data about tensile strength, yield strength, and the likes? Say for example reinforcing bars. Grade 40 Rebars are rated at 70,000 PSI for its ultimate ...
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3answers
280 views

How much further can I throw a baseball (148 grams) than a grenade (453 grams)?

Question: Over a flat plane, how much further can I throw a Major League baseball than I can an M67 grenade? Major League baseball: 148 grams M67 frag grenade: 453 grams For a baseline of how ...
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5answers
7k views

If the earth has gravity, why don't we all collapse to the center?

I'm sorry if the answer is obvious for you guys, but why don't we all (including buildings, road, people, the ground) collapse to the center of the earth because of gravity? Is it because we have ...
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3answers
6k views

Net work done on the body when we lift it and put it on the table is zero?

I'm little confused here. Work done on the body when we lift it and put it on the table is zero, because according to work energy theorem, change in kinetic energy of the body is zero. So, the net ...
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1answer
158 views

Net Force on Individual Masses, or the entire system? [closed]

In the picture, would the net force on each individual mass take into account both masses or just the individual mass? For example, would the net force on the first mass be equal to $am_1 = ...
2
votes
1answer
501 views

Increase in kinetic energy as some one walks to the centre of a merry-go-round?

When someone walks to the directly centre of a merry-go-round the total kinetic energy of the merry-go-round and person system increases. (assuming the kinetic energy due to the person walking to the ...
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1answer
26 views

Can the nonlinear hydrodynamic forces be neglected when a capsized ship is righting? [duplicate]

Can the nonlinear hydrodynamic forces be neglected when a capsized ship is righting? Thank you for answering my question.
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2answers
86 views

Can we harvest energy from constant gripping?

Gripping things hard needs energy even though nothing really moves. So I think we could harvest energy from this action, but I know that any type of energy harvesting requires moving parts. So can ...
1
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1answer
104 views

Confused about gravitational potential energy [duplicate]

So learning the concept of gravitational potential energy, my professor says that when lifting an object without any acceleration, the force we exert on the object to lift it is the same as the force ...
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0answers
42 views

Addition of forces in dielectric material

In this paper (page 2 of document) it is said that: Because this calculated force was comparable to the gravitational force, they assumed that the same would be true for the forces on a ...
4
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6answers
687 views

What is the relationship between force and momentum in collisions?

I know that $ \Sigma F = \Delta mv/\Delta t$. But if we had a marble that moves in a straight line at a constant velocity and colloids with another marble. Because of the law of conservation of ...
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1answer
89 views

Hooks Law and acceleration [closed]

A 435 gram sharpened piece of iron rebar into a spring loaded device. It takes a force of 355 Newtons to compress the spring by 27.5 cm. With what speed does the rebar shoot out of the device? ...
3
votes
1answer
99 views

Fruit flies in a bell jar [duplicate]

You place a bell jar on a scale and the scale registers x grams. You then trap y grams of flying, non-landing fruit-flies in the bell jar. What does the scale register? x grams? x+y grams? Something ...
1
vote
1answer
757 views

For a massless pulley moving upwards with acceleration, is the upward force equal to the downward force?

Imagine a massless and frictionless pulley with two weights hanging either side of the pulley by a massless string. Like this except not attached to a ceiling Rather than being fixed to a ceiling, ...
3
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2answers
931 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 ...
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1answer
7k views

Problem solving moments in equilibrium

Two straight ladders, AC and BC, have equal weights $W$. They stand in equilibrium with their feet, A and B, on rough horizontal ground and their tops freely hinged at C. Angle CAB = 60$ ^o$, angle ...
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6answers
2k views

Why $F=ma$ and not $F=m\dot{a}$?

What would happen if instead of $F=m*d^2x/dt^2$, we had $F=m*d^3x/dt^3$ or higher? Intuitively, I have always seen a justification for $\sim 1/r^2$ forces as the "forces being divided equally over ...
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1answer
59 views

Why does gravity enact force? [closed]

Gravity would cause two objects in a vacuum to move toward each other. I understand that gravity is a force that exists as a product of energy's original conversion into mass and the continuing change ...
1
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1answer
64 views

Generating forces precisely [closed]

When we like to produce known forces, we know that standard weights acting vertically on a object creates a known force. Now, what are the other methods to generate forces with accuracy? It is a 'do ...
5
votes
2answers
867 views

Deriving the Coulomb force equation from the idea of photon exchange?

Since Newton's law of gravitation can be gotten out of Einstein's field equatons as an approximation, I was wondering whether the same applies for the electromagnetic force being the exchange of ...
1
vote
1answer
372 views

Choosing the right point when calculating moments

A body is composed of two straight pins that are joined at a right angle. They have lengths $a$ and $b$ and the mass per unit length is $\rho$. When the body is balanced on a flat surface, as shown, ...
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2answers
255 views

Effect of movements of astronauts on International Space Station

I know that astronauts move in and around in ISS. When they move they also touch the modules of ISS and sometimes they apply force on the module to move. When this happens, as far as I know it affects ...
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1answer
176 views

Coulombs Law step by step help

How do you calculate the the magnitude of the total force of three charges and also the angle it makes with the x-axis? Knowing the magnitude and also the 2d co ordinates of the charges. I have ...
0
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1answer
33 views

With what speed must e.g. a car drive into a turn so it won't drift out? [closed]

I am trying to figure out the following question: with what speed must e.g. a car drive into a turn so it won't drift out (if a turn is a circumference of a semicircle)? e.g. $r= 5 m$ $a_r= ...
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0answers
162 views

Collision force calculation with no future knowledge

For a personal project, I am attempting to write a fairly realistic collision simulator (for relatively large objects, not quantum stuff). As I was consulting my physics textbook and various online ...
9
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1answer
1k views

Would you die before reaching the ground?

If you were to jump off a tall building, let's say Burj Khalifa, is it true that the pressure difference would be so strong as to kill you before reaching the ground?
3
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4answers
403 views

Potential Energy Concept

Imagine a book that we lift it with a force that is exactly equal to the force of gravity so the forces cancel out and the book moves with a constant velocity. Consider the situation after the book ...
1
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1answer
3k views

Final velocity of a spring [closed]

I need to calculate the velocity of an object when it is thrown by a spring; we have to calculate the velocity from $U=\frac 12 kx^2$. Now I know that $U=L=F\cdot S$ and $S=\frac{v_f^2-v_0^2}{2a}$. ...
5
votes
1answer
297 views

Pendulum in a Turning Airplane

My friend and I are having an argument over what happens with a pendulum hanging inside an airplane during a turn. Assuming that the airplane is making a standard 1 G coordinated turn, how does the ...
1
vote
1answer
99 views

Is there an equilibrium for water and air in a tank?

I'll try my best to explain my question with examples because I don't have much knowledge on the theory. So say that I had a block of water in air, a cube of water, that is dropping. If the cube ...
2
votes
1answer
239 views

Just for confirmation: About conservative forces [closed]

Once I posted in the following thread and wondered, how I could picture/understand conservative forces best. I think, that I understood my problem now and everything became clearer. So just for ...
0
votes
1answer
111 views

Foucault currents with a simple pendulum

I have this diagram : It's a kind of pendulum; when it swings, it passes through a small aera where there is a magnetic field. Therefore, the electrons moves towards the bottom because of a Lorentz ...
0
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1answer
63 views

Calculation of the g-force acting on people in a fake fun ride

I saw this video: https://www.facebook.com/video.php?v=622261007879030&set=vb.100002854081079&type=2&theater If you go to minute 1 and 2 seconds you see a fun ride in action. Obviously ...
1
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1answer
147 views

Wheel dynamics: reaction forces with ground

I am confused by part of a dynamic model in this paper: http://waset.org/publications/4405/real-time-control-of-a-two-wheeled-inverted-pendulum-mobile-robot see page 3, figure 5. All forces labeled ...
-2
votes
1answer
719 views

If a 2,400 lb. car is moving at 1 mile per hour, how much force is required to stop its motion? [closed]

Given that I stand behind or in front of a car and someone will move the car from within at approximately 1 M.P.H., how much force is needed to stop the force driven by the engine to put the car at ...
0
votes
1answer
473 views

What is the net force acting on a climbing man by the rope?

I am confused with determining the net force on the climbing man below by the rope. My analysis is as follows. Let the tension be $T$. As both hands hold the rope then there are $T+T=2T$ upward acting ...
0
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1answer
82 views

Hydrogen bond and van der Waals bond

Just now I am studying about hydrogen bond and van der waals bond. I understand and able to differentiate between them but thinking of the similarities, do they have any?
2
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2answers
1k views

Weight versus gravitational force [duplicate]

What is the difference between weight and gravitational force? I am a beginner who want to study physics properly.
2
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0answers
217 views

Odd experiment results (electromagnetics)

Okay, a bit of background. So I'm working on a linear accelerator (you might know it as a Gauss rifle), and I had worked through the equations I thought I needed (Magnetic force, displacement, etc.) ...
1
vote
2answers
298 views

Why did I get this dynamics question wrong? [closed]

I'm wondering as to why I got this physics question wrong, despite it being quite simple in nature. I believe that I missed something while working on the problem. Basically, the question involves ...
2
votes
2answers
447 views

Nature of tension in a massless rope [duplicate]

I'm faced with a conceptual problem, where I am supposed to describe the motions of the following system (two masses on each end of a totally inelastic rope hanged on a pulley): I understand that ...
3
votes
1answer
187 views

Confusion with Newton's Second Law : Position & Time Dependence of Force

For a conservative force $\vec{F}(x,y)$ we have $$\vec{F}(x,y) = - \vec{\nabla}\phi(x,y)$$ where $\phi(x,y)$ is a potential function for $\vec{F}(x,y)$. Again, Newton's second law states that $$ ...
1
vote
1answer
353 views

How does the weight of the pendulum's bob cause a torque?

I know that a force will cause a torque if the force has a perpendicular component to the distance from the pivot point. However, in the figure above, I can't seem to visualize how the weight of ...
21
votes
7answers
16k views

What does it mean to say “Gravity is the weakest of the forces”?

I can understand that on small scales (within an atom/molecule), the other forces are much stronger, but on larger scales, it seems that gravity is a far stronger force; e.g. planets are held to the ...
2
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2answers
106 views

Estimating the force needed to increase height of a mountain?

How would you estimate the force required by a tectonic plate to make the height of a mountain increase when it pushes against another? I've used a method to try and do it for Mt Everest and have ...
1
vote
1answer
123 views

Fictitious forces and $\omega$

I have been studying fictitious forces, such as the centrifugal force and Coriolis force. The equation for the centrifugal force is given by: $$F_{centrifugal}=-m\omega\times(\omega\times r)$$ My ...
0
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1answer
35 views

Various springs acting on a point mass

The force exerted on one spring is $\vec{F}=-k\vec{r}$. Now suppose we have N slinkys with stiffness $k_1,k_2,k_3,...,k_N$ where they have one end tied to fixed points in space with coordinates ...
1
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1answer
54 views

Joules To Move A Kilogram In Space [closed]

If roughly ten joules lifts one kg on earth one meter, how many in space? Meter / joule/kilogram Kilogram/meter/joule