4.342 forces questions.

How can I apply statics to a (real life situation) hanging white board?

0 answers, 13 views forces free-body-diagram statics
Im curious what solving a statics problem of a hanging white board can tell me. My whiteboard recently fell because the sticky hook peeled off the wall. By finding the tension forces in the string ...

5 Lagrange: when a potential force, when a generalized force?

Consider the following case of a drum unrolling a mass that is on a massless string wrapped around the drum: According to my professor, here we must consider the mass $m$ being in a gravitational ...

2 Why is “degeneracy pressure” not considered a force? [duplicate]

When you try to put two electrons or neutrons close together (e.g. in a white dwarf or a neutron star), these spin-$\frac{1}{2}$ particles, by the Fermi principle, tend to push each other apart. For ...

2 In which direction does the friction act in a circular motion?

I want to know how a body moves on a circular track. Suppose a car enters a circular path. If I don't turn my steering wheel, then the car would travel in straight line and perpendicular to the radius ...

1 How should I think about a block-and-tackle configuration weight-lifting machine?

At my gym, some of the weight machines provide a double mechanical advantage using a gun tackle pulley configuration. For a long time when I was using such machines, I convinced myself that if I were ...

What are the forces acting on a book kept on the ground?

If we exclude the motion due to the rotation of the Earth, what are the forces acting on the book? I know about the force of mg acting on the book and its opposite acting on the Earth, but I have some ...

2 Force of a solenoid on a ferromagnetic material

As I was trying to find an answer to another problem, I was informed that the equation I was using would not work. The equation I was using was $$F = (NI)^2\mu_0\frac{\text{Area}}{2g^2}$$ If this ...

58 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 ...

-2 Is magnetic Field conservative in nature?

Is magnetic field conservative in nature? Magnetic field lines do go in closed paths but that's not the definition of conservative. Rather, a field is conservative when the force on a test particle ...

-2 How to determine the tensions in a particular rope and two blocks arrangement? [on hold]

How do I find out the tensions $T_1$, $T_2$, $T_3$, and $T_4$ in the arrangement in which two blocks of 1 kg and 2 kg are hanging through a rope which is making an angle of 45 degree and 60 degree ...

Varignon's theorem (Principle of moments) failure?

Varignon's theorem states that "If many coplanar forces are acting on a body, then the algebraic sum of torques of all the forces about a point in the plane of the forces is equal to the torque of ...

A block on inclined plane

A block of mass $m$ is placed on an inclined plane (a ramp). If a constant force $f$ is applied to the ramp so that it is accelerating horizontally at a proper rate, the block will remain at the same ...

12 Why does a car engine not do work if the wheels don't slip?

I saw this mind boggling result that if the tires don't slip then the work done by an engine to move a car is zero. Why is this true? Moreover, what does this truly mean? Update: Sorry about not ...

1 Discrepancy in general work and pressure-volume work

2 answers, 56 views thermodynamics forces work
Consider a massless, frictionless piston fit into an airtight container containing an ideal gas. And let us say that the gas undergoes quasi-static isothermal expansion by lowering the pressure ...

2 Work done in force field

0 answers, 24 views forces work

-6 How exactly does mass affect speed? [on hold]

2 answers, 74.705 views newtonian-mechanics forces mass speed
I know that mass affects weight, and weight is a force, and $F = ma$. So how does mass affect speed?

10 What is the relationship between force and kinetic energy?

5 answers, 132.471 views newtonian-mechanics forces energy work
I have learned that $$\mathbf{F} = m \mathbf{a}$$ where both the force $\mathbf{F}$ and acceleration $\mathbf{a}$ are vectors. This makes sense, since both force and acceleration have a direction. On ...

19 Can the Lorentz force expression be derived from Maxwell's equations?

5 answers, 9.086 views electromagnetism forces maxwell-equations
The electromagnetic force on a charge $e$ is $$F=e(E+v\times B),$$ the Lorentz force. But, is this a separate assumption added to the full Maxwell's equations? (the result of some empirical ...

Determining the direction of a force with a dynamometer

1 answers, 17 views newtonian-mechanics forces
I'm taking what is usually called "freshman's" mechanics course, and I'm basically trying to understand how forces are measured and determined. Starting with the definition of the procedure for ...

1 Conservation of angular momentum in a rod with hinge on one end

Consider the case a rod with hinge on one end in horizontal position. At the instant when it is released, the weight of the rod is going to give it a torque with an acceleration. Why is angular ...

-2 Ball in a Bowl (Circular Motion) [closed]

I know similar questions have been asked already but I've been struggling on this for ages so I have come for help. A hemispherical bowl of radius $r$ is fixed with its rim horizontal. A bead B of ...

-4 Maximum force in tug of war

In tug of war, The maximum force that a person can exert on the rope depends on the static coefficient of friction. Is that correct?

1 What does it mean if the dot product of two vectors is negative?

If the dot product gives only magnitude, then how can it be negative? For example, in this calculation: W = \vec{F}\cdot\vec{r} = Fr\cos\theta = (12\ \mathrm{N})(2.0\ \mathrm{m})(\cos 180^\circ) = ...

1 Force and momentum of water striking a water wheel?

Imagine water striking a water wheel. We can find the torque applied by calculating the force of the water and multiplying by the distance from the center. To calculate force, we can use the formula ...

What force does the dynamometer show in this case? [duplicate]

1 answers, 26 views newtonian-mechanics forces
So I came across this picture on facebook My logic says it should show 200N, because you are pulling it with 100N on each side. On the other hand (as one of the facebook comments also stated, also ...

Friction and Motion

2 answers, 46 views newtonian-mechanics forces friction
We know that the frictional force always opposes the relative motion. Recently, I happened to read somewhere that "It is the frictional force which causes a car to accelerate on road". My question is ...

1 Gravitational forces become as strong as other fundamental forces

0 answers, 27 views thermodynamics forces
I was doing some reading on Absolute hot and was wondering what this actually means: ...

How do particles in a wave make the next particles move?

1 answers, 1.059 views forces energy waves
I only know few things about waves, but this question just popped up in my mind. I already know that particles transfer energy to each other,but I do not know HOW they do it! The truth is that I ...

-6 Rail Gun in Space [closed]

0 answers, 43 views forces space
POTUS was talking about a Space force and people laughed. Not me, it is his desire to rid the world of nukes and make the world a safer place. He would also like to be able to take out the bad ...

6 Relative size of the 2 tidal bulges

3 answers, 1.065 views forces newtonian-gravity tidal-effect
I am interested in making a simplified model that represents only the effect that the moon has on Earths tides. In this model I am going to assume that the earth is completely spherical (with no ...

Two-particle system: proof force on each particle can be derived from one potential energy

Suppose we have a two-particle system with particle 1 and particle 2 that obeys Newton's laws. Further assume that the force on particle 1 due to particle 2, $F_{1, 2}$, is conservative. I know then ...

String applying a force on pulley

Why should string apply a force on pulley? (like atwood machine cases) and does that mean the pulley will exert an equal force on string (newton's third law)? Please explain in detail,if possible ...

-1 Calculating breaking rpm/force of a spinning ring [closed]

Let's suppose I have a ring of mass m, and radii r, thickness t, and width w, as shown: I would like to come up with a way to be able to work out the highest RPM a ring can reach given m, r, t and w, ...

-2 Spring block systems [closed]

Calculate compression from ground frame

How to distinguish between applied forces and forces of constraint?

Is there any generic prescription to separate the set of applied forces to the set of forces of constraint with respect to any arbitrary physical system?

Calculating shear stresses with multiple forces

I have a rigid body where multiple forces (green) of different magnitude are applied. If I sum up the parallel component of the forces and divide it by the surface area, I can get the average shear ...

Newtons third law explanation on a push of table [duplicate]

1 answers, 56 views newtonian-mechanics forces
I read this example of pushing a table with your hands. So the force is applied on the table to push and the table exerts the same amount of force on our hands. My question is, if the forces are ...

How to find the shear stress and bending moments of uninform distributed load [closed]

1 answers, 40 views homework-and-exercises forces moment
I can't for the life of me find a way to solve this. Given is the length of a T girder, which is fixed at one and on rolled support on the other side Now in the exercises given during class there ...