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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54 views

Calculating the rate at which a car turns

This is going to be difficult to describe, as I have no real concept of this sort of physics, so please bear with me. If this is too much or beyond the scope of this website, I apologize. I am making ...
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1answer
42 views

Question about resolving forces

Say, in the example below, the weight $mg$ of the object is $800N$. To find $R$, the conventional method is to use $R\sin(28^\circ) = 800$. But why isn't it possible to use instead the component of ...
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1answer
146 views

A moving charge in an uniform magnetic field

An electron is in a region where there is an uniform magnetic field created by a large disc-shaped magnet. As is well known, if the electron is moving with velocity $\vec v$ parallel to the flat ...
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3answers
161 views

If something that is moving at constant velocity has no net force acting on it, how come it is able to move other objects?

Let's say 10 kg block is sliding on a frictionless surface at a constant velocity, thus its acceleration is 0. According to Newton's second law of motion, the force acting on the block is 0: $a = ...
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1answer
56 views

How can the tension force be computed to test if a shape is moving or not?

Source Given the coordinates of $n$ 3D joints ($1kg$ each) connected by $m$ rods. Assume rods have zero mass and joints with $z=0$ are fixed to the ground while others are free to move, will the ...
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1answer
87 views

Finding friction forces of stacked boxes on a table

Consider the following system. The given friction coefficients are for static. Let $g=10$ (meter per square second). If the $F(t)=10t$, for example, determine the friction forces $f_{AB}(t)$ ...
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1answer
26 views

Modulus of action-reaction forces

I read somewhere that action-reaction forces satisfy the form $$ \mathbf{F}_{12}=-\mathbf{F}_{21}=f(|P_1-P_2|)(P_1-P_2) $$ meaning that the modulus can only depend on the distance between the two ...
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1answer
57 views

Upthrust vs Drag

24: A ball is falling at terminal speed in still air. The forces acting on it are upthrust, viscous drag and weight. What is the order of increasing magnitude of these 3 forces? ...
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4answers
67 views

Relation between Force, Time, and Energy

Is energy involved independent of force applied over time? In other words, if I wish to apply a force for much more time would I require more energy?
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1answer
61 views

Why mountain roads are winded up rather than keeping them straight?

In my opinion,to prevent the line passing from the center of gravity of a body(e.g bike or car) trying to climb the mountain or hill to fall outside the base of support so to maintain stable ...
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1answer
81 views

Confusion with curl of Lorentz magnetic force

Since the magnetic force is a no work force, $dW=\vec F\cdot d\vec r=0$ for $\vec F(\vec r)=q(\vec v(\vec r) \times \vec B(\vec r))$, therefore $\oint \vec F \cdot d\vec r=0$ by Stoke's theorem. ...
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1answer
86 views

Truck moving uphill, object suspended from ceiling, determine acceleration [closed]

A truck is moving with constant acceleration $a$ up a hill that makes and angle $\phi$ with the horizontal. An object of mass $m$ is suspended from the ceiling of the truck by a light cord. If the ...
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1answer
193 views

Pseudo Force Other Than Centrifugal Force In A Rotating Frame

I read in HC Verma that if we are observing the motion of a body from a rotating frame and the body under the observation is NOT in motion with respect to our frame than centrifugal force is the ...
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4answers
2k views

When we do pull-ups , does the bar takes more weight than when we hang down on the bar?

When I do pull-ups, I feel I push down to the bar. But does the bar really take more weight than just hang down? For people who don't know pull-ups and hang down, here is an illustration. Left: Hang ...
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1answer
96 views

Find the tension and angle from a vertical of a rope hooked up to an object

Below is the homework problem I am working on: A 18.3-kg object hangs in equilibrium at the end of a rope (taken as massless) while a wind pushes the object with a 63.9-N horizontal force. Find ...
2
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3answers
117 views

How come water in a cup won't shoot out of a straw placed inside it?

I've been learning about pressure and fluid dynamics, and I've stumbled onto a problem. Say you have a straw in a cup. The surface area of the water in the cup is much greater than that of the straw. ...
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1answer
57 views

Falling metal cylinders more devastating than a nuke?

I just saw G.I JOE - Retaliation. In the movie the bad guys (spoiler alert) Could this device cause more destruction than a nuclear weapon? If so, how?
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2answers
94 views

Schroedinger equation. Why Potential energy instead of Force?

What is the reason Schroedinger equation is quoted in terms of potential energy instead of force?
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0answers
33 views

Balloon tethering cable tension model (catenary tether)

If a moving balloon (let's say it's a blimp system with some rotors for movement) is connected to the ground by a cable that describes a catenary curve, how can we model the tension being applied on ...
2
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0answers
42 views

what forces are present when slicing an object.

I found here:What happens when we cut objects? that it is due to fracture wood splits open when using a wedge. Does it only apply when the wedge is already in the wood? How about the moment before a ...
6
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4answers
194 views

If I bury a cylinder (top end sealed) in sand, how much force do I need to pull it out?

Let's say the cylinder has a diameter equal to its height of $25\;\mathrm{cm}$ the cylinder is sealed at the top and filled with sand the cylinder is also buried in the sand at sea at a depth of ...
13
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2answers
2k views

Why do ships lean to the outside, but boats lean to the inside of a turn?

Small vessels generally lean into a turn, whereas big vessels lean out. Why do ships lean to the outside, but boats lean to the inside of a turn?
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3answers
1k views

MotoGP motorcycles lift front wheel while exiting curve

I've seen multiple times now in MotoGP that motorcycles were leaving a curve, and because of the acceleration the front wheel is slightly leaving the ground. But at the same time they were still ...
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6answers
192 views

Is gravitational force affected by intervening medium?

If we leave a iron ball and feather into the water, feather returns to the surface and floats or moves into the water slowly. On the other hand, iron ball (of certain mass greater than mass of ...
77
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8answers
8k views

Why does a helium filled ballon move forward in a car when the car is accelerating?

I noticed that when I had a helium filled, latex ballon inside of my car, it moved forward in the cabin as I accelerated forward. The faster I accelerated forward, the faster the ballon went from the ...
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2answers
103 views

Universal gravity at small distance

Could it be that there is simply a maximum gravitational force that two bodies of finite mass can exert on one another? This would occur at $r=0$, so maybe there is some really really really small $a$ ...
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2answers
170 views

Why do two equal-and-opposing forces each do work on a moving object but not on a stationary object?

Consider a point-mass $m$ having constant velocity but undergoing influence from two forces, $F_1$, $F_2$, having equal magnitude but opposite directions. Because the forces' magnitudes are equal, I ...
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0answers
42 views

How would you explain the difference between these situations?

I have been thinking about this for quite a while, but I just can't seem to formulate a coherent answer. In problem which I will denote (a), we have a man sitting on some sort of chair and he is ...
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0answers
55 views

Visualizing Tension in FBD — Rope With Mass

Asked to find the tension of a point that is halfway up a rope (where the rope has mass), given the system: The solution of the problem (FBD included) is as follows. In this diagram (Tm = tension ...
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2answers
61 views

Is the moment of a force the same about any point?

I know that when a body is is equilibrium There is zero resultant force in any direction, i.e. the sum of all the components of all the forces in any direction is zero The sum of the moments about ...
6
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2answers
349 views

Can molten metal be suspended in air?

I wondered if magnets could be used to hold a drop of molten liquid metal in air (not for any particular reason just because it could be done), but was disappointed when a quick Google search showed ...
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3answers
329 views

Why does a bicycle come to rest after travelling a distance?

According to Newton's law of motion, an object that is in motion will not change its velocity unless an external force acts upon it. In the case of a bicycle, if it is in motion with a certain ...
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0answers
92 views

Forces, symmetry, and asymmetry

The concept of symmetry is one of the most promising and misunderstood concepts in physics. If one consider Hermann Weyl ("Symmetry"; ISBN-13: 978-0691023748), "As far as I see, all a priori ...
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2answers
91 views

Is a particular force different in different frames

Can a particular real force have different magnitude in different frames?
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3answers
3k 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 ...
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2answers
172 views

When pressure is exerted on parallel hydraulic pistons, do they start extending at the same time?

If there are two hydraulic cylinders connected in parallel, each with a different load (shown in the picture below), will they start extending at the same time? I'm having a disagreement with my ...
3
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2answers
138 views

Does “Crack The Whip” actually speed you up?

"Crack The Whip" is a game played on ice skating rinks where several individuals line up all facing the opposite end of the rink, and skate forward. When the group reaches the opposite end of the ...
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3answers
292 views

Protons and Electrons Occupying the Same Space

When it comes to atoms electrons can't fall into the nucleus, which besides the off hand uncertainty explanation, I'm not sure which force prevents them from falling into the nucleus. I thought I ...
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1answer
75 views

Why must spacecraft reach escape velocity to escape Earth (or any other big object)?

I think I have learned in physics that escape velocity is defined as the speed at which objects going ballistic in the opposite direction of the main gravitational force are able to finally overcome ...
2
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2answers
49 views

Can a force applied to a wheel find the fastest way of getting to the other side?

I haven't studied much about this, so if I am mistaken about something please correct me. From what I have seen around the Internet, a force applied to a object takes time to propagate through the ...
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5answers
163 views

Acceleration is zero, for non-zero net force

I understand a problem like this has already been asked, but I have not found an answer that makes it clear. A force is applied to a box on a table(lets ignore friction), and the box moves with some ...
5
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2answers
293 views

Does the mass of a star change as it collapses into a black hole?

I know (I think!) that when a really big star collapses on itself it creates a black hole. My question: When a star collapses, is the mass equal to the mass of the star when it's not a black hole? Or ...
0
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3answers
173 views

Gravity force between two objects with different mass

We know thanks to Newton that: $$F=G\frac{m_1\cdot m_2}{r^2}$$ Where $G$ is the Gravitational Constant that is about $6.673\cdot10^{-11}$ $m_1$ and $m_2$ are the masses of two different objects ...
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4answers
390 views

Does a charge experience no force due to electric field produced by it?

My book "Concepts of Physics (Satish K. Gupta)" says: The electric field of a charge is the space property by virtue of which the charge modifies the space around itself. As a result, if any ...
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2answers
52 views

Find the tangential acceleration

A racing car driver drives his car on a flat circular track of radius $\frac{25}3 m$ and a coefficient of friction $0.5$. Find the magnitude of its tangential acceleration (in $ms^{-2}$) at an ...
0
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1answer
66 views

Ball thrown in a moving train [duplicate]

A ball is thrown upward in a train moving with a constant velocity. Where will it land? My intuition tells me that the ball will fall at my back. But my book says that it will return back to the ...
5
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7answers
789 views

In calculating work done by a constant force over a constant distance, why doesn't the subject's initial velocity matter?

Assume a point-mass $m$ is travelling in a straight line, and a force $F$ will act on $m$ (in the same direction as $m$'s velocity) over a constant distance $d$; why doesn't $m$'s velocity matter to ...
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1answer
39 views

A pearl that moves in a smooth vertical hoop

I wanted to ask about the situation of a pearl that moves in a smooth vertical hoop in circular motion as described in the following sketch. According to a simulation found in the internet , a ...
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1answer
57 views

One proof of linear momentum of the system [closed]

I copy and paste all the proof here, but I'm confused about the last step, which is that the summation of the internal force and be written as two other summations.
3
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0answers
36 views

How much weight is lifted from each side? [closed]

I don't know the math to do this, so I am asking here if someone can work this out with all of the details I'm providing. Total mass EST.: 2,400 lbs. Length from front to back: 14 feet 6 inches. ...