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 ...
0
votes
1answer
33 views
Find the bending moment of a pole attached to a moving block
I'm having trouble with the following problem.
What I've done so far:
x-y is the usual coordinate system.
$a=\frac{F}{m}=\frac{800}{60}$ and the y component of this is $a_y=a\sin{60^\circ}$.
To ...
0
votes
0answers
74 views
Tension $T$ in cable [closed]
Calculate the tension $T$ in each cable, as well as the magnitude and direction of the force exerted on the strut by the pivot in each case mostrados.En systems, w is the weight of the suspended box, ...
1
vote
2answers
66 views
Resolution of vectors
What is the fundamental basis of resolution of vector. Suppose we have a vector $\vec{mg}$, now we resolve it into two components, horizontal and vertical. My question is what is the basis for telling ...
3
votes
3answers
139 views
Non-SHM oscillatory motion
How to solve these kind of questions , where $|F| \propto x^2$?
How to find time period and velocity type related things to the oscillatory motion?
...
-1
votes
3answers
131 views
What needs to be integrated to solve this problem?
An object is placed on a frictionless table with its one end attached to a cord which is connected to a pulley and the tension is maintained constant at 25 N. what is the change in kinetic energy ...
0
votes
1answer
49 views
Measuring vibration and converting to force (N)
The test is:
To have a rotating machine, bolted into a factory floor.
To measure the vibration on 3 axis (output of accelerometers can be acceleration or velocity in $\mathrm{m/s}$ or ...
0
votes
1answer
62 views
Find the dielectric constant of the medium?
Two point charges a distance $d$ apart in free space exert a force of $1.4\times10^{-4}N$. When the free space is replaced by a homogeneous dielectric medium, the force becomes $0.9\times10^{-4}N$. ...
0
votes
0answers
42 views
Do all the 4 forces of nature act at the same speed? [duplicate]
It is believed that gravity, the weakest of the four forces propagates at the speed of light, cf. e.g. this Phys.SE post. One would expect (perhaps erroneously) that the other, stronger, forces acted ...
0
votes
1answer
90 views
Shear Flow corresponding to Eccentric Shear Force of a Closed-section Beam (Structural Analysis - Mechanics)
Been stumped with this question for way too long... its a beam with a thin-walled rectangular cross-section, and a shear force is acting at a distance from the shear center. I know my decomposition of ...
2
votes
1answer
63 views
How does the buoyant force on a cube at the bottom of a tank of water manifest itself?
Let's say a 10N cube (in air, on Earth) rests flat on a scale at the bottom of a tank of water, and the scale reads 8N, so there is 2N of buoyant force on the cube. How does the buoyant force ...
4
votes
2answers
133 views
Relativistic Lorentz force law
If we consider the the relativistic Lorentz force law:
$$\frac{d}{dt} (m\gamma \vec{u})=e(\vec{E}+\vec{u} \times \vec{B})$$
How can we deduce:
$$\frac{d}{dt} (m\gamma c^2)=e \vec{E} \cdot \vec{u}$$
...
0
votes
1answer
33 views
Work done by complex field on complex plane
A force field is given by $F = 3z+5$. Find the work done in moving an object in this force field along the parabola $z = t^2 + it$ from $z = 0$ to $z = 4+2i$.
I don't understand why conjugate ...
1
vote
1answer
73 views
Hydrostatic pressure at lateral directions
I just read that, with respect to a stationary tiny cube, suspended in a fluid, that has a negligible weight and dimensions:
Pressure is the same in every direction in a fluid at a given depth, ...
-1
votes
2answers
60 views
Changing Direction in a Vaccum [closed]
If a mass of one kilogram is traveling at one meter per second at 90 degrees, how much energy is required to get it to travel going 180 Degrees?
1
vote
3answers
132 views
Is the tension in both ends the same (on a massed string)?
If two blocks lay on a table and I pull the second block, as shown in the picture below. Is the tension in both ends of the string the same? (The string has a mass)
1
vote
2answers
96 views
Accelerating an elevator
A person is standing on a weighing scale in an elevator in upward acceleration.
Let $N$ be normal reaction force exerted by the weighing scale to the person (upward).
It is known that the person ...
1
vote
1answer
104 views
rate of change of spring potential energy $\frac{dU}{dt}$
Suppose we have a setup like this. In orange are two wooden sticks sort of things, and they are attached to the block of mass $m$(as usual) at a joint which is hinge type something. A similar ...
2
votes
3answers
106 views
Is electron velocity at induction higher than in a wire?
When looking to the electrostatic induction on a microscopic level, do the electrons really move with high velocities or they move like when a current passes through the wire (slowly).
1
vote
1answer
35 views
Can Joule's First Law of Thermodynamics be Applied to Atomic Charges?
James Joule established that all forms of energy were basically the same and interchangeable. My question is if thas law is relevant in particle physics. Can a positive charge and a negative charge be ...
1
vote
2answers
48 views
effect of vertical collision on kinetic friction and subsequent change in horizontal velocity
Suppose somehow a block of mass $m$ is moving on ground, and the coefficient of kinetic friction between the block and the block is $\mu_k$. If I drop a tennis ball(of same mass) on it from a ...
0
votes
2answers
102 views
How do you tell what forces do no work?
The total mass of the children and the toboggan is 66 kg. The force the parent exerts is 58 N (18 degrees above the horizontal). What 3 forces/ components do no work on the toboggan?
I said the ...
2
votes
1answer
123 views
Is there a geometrical way to obtain a relationship between these vectors?
Suppose we have a setup like this. Here $a_1,a_2,b_1,b_2$ are acceleration magnitudes($b_1,b_2$ being relative) and $P,Q,R,S$ are not pulley/blocks but are points on the rope. If I use a geometrical ...
2
votes
2answers
114 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 ...
0
votes
0answers
43 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
vote
1answer
112 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 ...
1
vote
1answer
131 views
Newton's Third Law of Motion
I want to start off by saying that I've looked around for other explanations, but I've not really found any satisfying ones. My question is basically the whole "Why can anything move at all?" ...
-1
votes
1answer
103 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 ...
0
votes
3answers
118 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 ...
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 ...
1
vote
1answer
118 views
Calculating the acceleration of a car
I'm trying to calculate the maximum acceleration a car can achieve with the current gear ratio. I am ignoring drag forces and friction to keep it simple.
I'm doing this by:
calculating the torque ...
0
votes
0answers
133 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
282 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 ...
2
votes
2answers
152 views
Cantilever Beam - Maximum Shear of the Beam
A cantilever beam $3\ \text{m}$ long is subjected to a moment of $10\ \text{kNm}$ at the free end. Find the maximum shear of the beam.
The answer is "There is no vertical load, shear is zero"
...
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 ...
2
votes
4answers
110 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
90 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 ...
4
votes
1answer
82 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
158 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
145 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 ...
0
votes
1answer
117 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 ...
4
votes
1answer
83 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
2answers
66 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?
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 ...
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
119 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.
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
56 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. ...
1
vote
4answers
202 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 ...
