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 ...
2
votes
4answers
109 views
Why in $F = iLB$, $L$ is a vector but $i$ is not?
I learned $F = iLB$ recently. However, I don't understand why $L$ is marked as a vector but $i$ is not.
For a normal rod, how should I define the direction of length vector $L$? And if I reverse the ...
3
votes
2answers
88 views
What causes acceleration of particles in the expansion section of a De Laval nozzle?
A De Laval nozzle has a compression section, where the propellant is compressed (and thereby accelerated) as it moves towards a narrow section (the throat). After the throat, the nozzle widens out ...
2
votes
2answers
113 views
Movement of man and ladder and their center of mass
Suppose there is a massless frictionless pulley.
A rope over it carries a mass $M$ and on other side carries a ladder of mass $(M-m)$ and a man on that ladder, of mass $m$. Now the man starts ...
1
vote
1answer
108 views
Work done by friction
Suppose we have a block of mass $M$ and we are moving it up a curve, very slowly ($a=0$). The surface is not smooth, and coefficient of friction is $\mu=\mu_s=\mu_k$.
To move the block we apply a ...
0
votes
0answers
42 views
Does distance increase force at impact? [closed]
If a car that weights 1800 KG is traveling at 2.235 ms would it with greater force and 25 feet than 10 feet?
My calculations say it would be the same if the road was level and the same surface ...
-1
votes
1answer
102 views
Vector Addition — Direction
Say we have three forces $F_1, F_2, F_3$, such that
$$
F_1 + F_2 - F_3 = 0\hspace 10mm (1)
$$
And let us say that $F_1$ and $F_2$ have the same direction and magnitude, and that $F_3$ has double the ...
1
vote
2answers
155 views
Is there any case in physics where the equations of motion depend on high time derivatives of the position?
For example if the force on a particle is of the form $ \mathbf F = \mathbf F(\mathbf r, \dot{\mathbf r}, \ddot{\mathbf r}, \dddot{\mathbf r}) $, then the equation of motion would be a third order ...
0
votes
3answers
115 views
Force with zero acceleration [duplicate]
If I apply a force on a body which is kept against a wall, then the body will not move. The body is not moving means that its velocity is zero, and hence its acceleration is also zero. According to ...
0
votes
1answer
143 views
Hooke's law, springs
A spring AB with constant k is hooked in the end A to the ceiling. At the end B of the undefomed spring is hooked a mass of weight 100N. At $t=0$ the mass is let free with no initial velocity. Not ...
0
votes
2answers
1k views
What is the force exerted on a body that doesn't move?
If I push against a brick wall I'm exerting a force against the brick wall the the brick wall will exert the same force against me. These will cancel each other out and neither myself or the wall will ...
4
votes
1answer
513 views
Hooke's Law question
I have the following question to answer:
a force of160 N stretches a spring 0.050m from its equilibrium position.
A. what is the spring constant of the spring?
The equation for Hooke's Law in my ...
2
votes
2answers
302 views
This is going to sound really stupid. But how do I change my normal force?
Suppose I am going to the doctor's and I want to do either of the following
Make myself lighter on the scale
Make myself heavier on the scale
For 2), isn't it just relaxing and let your mass drop?
...
1
vote
1answer
74 views
Work as an integral of mass over velocity?
As I've understood it, the area under $F$-$s$-graph is the work done, so then :$$W(s)=\int{F(s)ds}$$
I am also given this equation ($W_k$ is kinetic energy, which is equal the work done to set the ...
0
votes
2answers
271 views
When we throw an object in the presence of gravitational attraction is the mass of the object proportional to the time of fall or not?
I was confused when i saw two object of different masses (A and B)falling from the same height(h) but both of them strikes the ground at same time. Is this possible, that masses of the objects are ...
0
votes
0answers
128 views
Maximum Shear on a Beam - beam with fixed support on one end and hinge on other end
A beam $\displaystyle 3m$ long with fixed support on one end and hinge on the other end is subjected to a uniform load of $10\ kN/m$. What is the maximum shear of this beam?
The solution is this one:
...
0
votes
3answers
278 views
Force inversely proportional to the squared distance
Newton's law of universal gravitation:
"Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to ...
1
vote
1answer
49 views
Can we change frame of reference twice in a single problem?
My question has an inclined plane of mass $M$ and simple block kept on it, of mass $m$ (Both on a table). All surfaces are friction-less. Both of the objects would move, block down the incline and ...
4
votes
1answer
80 views
Finding the acceleration of a cart rolling on a table
The cart is rolls frictionless on the table. It has a mass of $1 kg$. Attached to it are 2 strings, that go through two frictionless sheaves. The weights have masses as in the picture.
...
1
vote
1answer
157 views
Omni-directional motion, resolving three or more vectors?
In robotics, there exists drive-trains that can move omni-directionally (that is in any direction). These come in many shapes and sizes, but most come in a three wheel or four wheel configuration, to ...
3
votes
1answer
265 views
Effects of parallel superconducting plates
Assuming the existence of virtual particle field ( zero point energy field) Casimir force is produced by 2 parallel conducting plates excluding some of the frequencies between the plates, if these 2 ...
2
votes
2answers
203 views
Small scale water power, how does water volume and hight convert into electric energy?
I was playing a little bit with the basic physics behind water power production but I can't get the numbers right.
Let's say that I put a windmill that pumps water into a watertank on the top of my ...
1
vote
4answers
201 views
Bat hitting a ball
When a bat hits a ball, consider two cases:
1) The batsman goes for a defense, and stonewalls it, to reduce its speed.
2) the batsman goes for a shot, e.g. a home-run, etc.
in which case will the ...
0
votes
2answers
86 views
Can there be energy with no force or energy with no power?
I think that both force (number of newtons) and power (p=ui(?)) implies that there is energy so we can't have force without energy and we can't have power without energy(?)
But can there be energy ...
3
votes
1answer
141 views
Origin of electric charge
Baryons have charges that are the result of a polynomial calculation of their building blocks (quarks)'s fractional charges. But what gives these quarks electric charges? What interactions do they ...
4
votes
1answer
82 views
How soon that a force affect another object?
Imagine this scenario: I have 2 objects in vacuum without any force exerted upon them not even a possible gravitational force between them.
Now if one of them gets a gravitational or magnetic force, ...
0
votes
1answer
114 views
A very elementary question regarding force of friction
When I first studied friction I faced f = $\mu$ N where f is force of friction, $\mu$ is coefficient of friction for the surface considered and N is the normal force for the body on surface. Now f is ...
0
votes
2answers
416 views
Calculating force of impact
Since $\text{force = mass}\times\text{acceleration}$,
is it right to say that an object traveling at a high
constant velocity (zero acceleration), exerts zero
force upon impact with a stationary ...
0
votes
2answers
65 views
Conservation of Momentum from Recoil Speed
A gun has a recoil speed of 2 m/s when firing. If the gun has a mass of 2kg and the bullet has a mass of 10g (0.01 kg) what speed does the bullet come out at?
The gun has zero total momentum before ...
2
votes
1answer
43 views
Reason behind cohesive and adhesive force
What is the real cause behind the cohesive and adhesive forces?
4
votes
3answers
781 views
Block on a block problem, with friction
Consider two blocks, one on top of the other on a frictionless table, with masses $m_1$ and $m_2$ respectively. There is appreciable friction between the blocks, with coefficients $\mu_s$ and $\mu_k$ ...
3
votes
2answers
1k views
Modeling a two-mass, spring, damper system
I'm trying to model a system with two masses, two springs, two dampers, and one applied force using transfer functions. I'll then be inputting it into Simulink.
The system looks like this but there ...
1
vote
2answers
221 views
Could someone remind me what this means again? $\nabla U = \pm F$
You know that for a potential function (conservative force/fields) that
$\nabla U = \pm \vec{F}$
In math, we don't have that minus sign, we have only the plus one.
What does it mean if you get rid ...
1
vote
0answers
42 views
effect of internal forces to a glider's descent
This is a continuation of a previous question, with more thinking applied, thanks to a helpful comment.
Imagine a glider is airborne in a breezeless sky. The glider is 3 KM high, is traveling at 100 ...
5
votes
1answer
116 views
Slinky base does not immediately fall due to gravity
Why does the base of this slinky not fall immediately to gravity. My guess is tension in the springs is a force > mass*gravity but even then it is dumbfounding.
2
votes
2answers
133 views
How can a train locomotive generate enough traction to pull all the coaches?
Sorry for posting what may be an obvious question but we just learning about friction at school and my teacher couldn't explain well enough to me and I would appreciate your inputs.
Consider the ...
0
votes
0answers
26 views
effect of internal force to a glider's descent [closed]
Imagine a glider is airborne in a breezeless sky. The glider is 3 KM high, is traveling at 100 KM / hr, and is descending at a constant rate of 10 m per min. The glider weighs 200 kg. The sole ...
0
votes
0answers
54 views
Work done by friction (homework) [closed]
A 40 kg case is pushed across a floor at a steady speed of 1.5 m/s. When the pushing stops, the case slides a further distance of 1.2m before coming to rest. Calculate the frictional force acting on ...
0
votes
0answers
27 views
How do I minimize the the stress created by fore-aft forces?
My friends and I are designing a bench press spotter. Essentially, when the user needs help lifting the barbell due to muscle fatigue, an arm on each side of the user raises to provide assistance. ...
2
votes
1answer
83 views
Explanation of a Foucault pendulum
The equations of motion of a Foucault pendulum is given by:
$$\ddot{x} = 2\omega \sin\lambda \dot{y} - \frac{g}{L}x$$
$$\ddot{y} = -2\omega \sin\lambda \dot{x} - \frac{g}{L}y$$
where $\omega$ is ...
2
votes
1answer
73 views
Is energy always proportional to frequency?
Google has no results found for "energy not proportional to frequency" and many results for E=hf. Is there an example of an energy that is not proportional to frequency?
1
vote
1answer
58 views
Static Friction work and Energy [closed]
I have this problem:
A 4.0 kg block is given an initial speed of 8.0 m/s at the bottom of a 20° incline. The
frictional force that retards its motion is 15.0 N. (a) If the block is ...
1
vote
1answer
205 views
Gravity force strength in 1D, 2D, 3D and higher spatial dimensions
Let's say that we want to measure the gravity force in 1D, 2D, 3D and higher spatial dimensions.
Will we get the same force strength in the first 3 dimensions and then it will go up? How about if ...
1
vote
3answers
328 views
What was meant by the 'ponderomotive force' as understood by Minkowski?
Skimming through Minkowski's famous 1907 paper, he uses the term ponderomotive force.
What does he mean by this?
0
votes
1answer
51 views
Potential energy and average force? [closed]
A body of mass $15\,kg$ originally at rest $5\,m$ above the ground falls and penetrates $15\,cm$ into soft earth.
Determine the loss of potential energy
Determine the average
resistance of the ...
2
votes
3answers
122 views
Explanation on the resulting forces of two positive point charges
Why will the resulting force lines of two positive point charges be like this:
I would expect this:
2
votes
2answers
149 views
Fictitious forces confusion
I have a hard time understanding the subject of fictitious forces. Let's discuss a few examples:
1) I'm sitting inside a vehicle which is accelerating in a straight line. I feel like someone is ...
0
votes
1answer
59 views
Do all forces act in the same way where gravity is close to zero?
Suppose that I put in the outer space (where gravity from other bodies is negligible) a large, perfectly round sphere totally filled with water. At the bottom (even though "bottom" doesn't make much ...
-4
votes
1answer
6k views
What is the extent of Earth's gravitational pull?
Where the gravitational pull of Earth exist up to?
What distance from Earth it will be zero?
How do the skydivers fly at a same altitude?
Won't they feel gravitational pull?
What is the Earth's ...
2
votes
3answers
130 views
Is restoring force a particular type of force?
I have a question about the restoring force in elastic band or rope which confusing me for a long time.
As I was told in high school physics, for an elastic band (or spring), if Hooke's law holds, we ...
1
vote
0answers
49 views
Where do electrons get the energy to remain in orbit? [duplicate]
As we know electrons continuously revolve around the nuclus without falling in it at a high velocity beating it's force of attraction. My question is where do electrons get energy to revolve around ...
