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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2
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3answers
979 views

Why does a rod rotate?

I'm a physics tutor tutoring High School students. A question confused me a lot. Question is: Suppose a mass less rod length $l$ has a particle of mass $m$ attached at its end and the rod is ...
4
votes
2answers
1k views

Physics behind the flow of gas coming out of a balloon

I'm working with stratospheric balloons (latex ones) and I want to put a valve on it so it can float for a longer time. I'm trying to define which valve I should use, which demands I estimate the flow ...
1
vote
1answer
487 views

Convert a 200mm linear stroke into 90 degrees motion [closed]

Can anyone help me Convert a 200 mm linear stroke into 90 degrees motion with as much mechanical advantage as possible or into two 90 degrees motions with as much mechanical advantage as possible? ...
3
votes
3answers
2k views

How do forces work

Is there a mechanistic-type explanation for how forces work? For example, two electrons repel each other. How does that happen? Other than saying that there are force fields that exert forces, how ...
10
votes
2answers
578 views

Is acceleration an average?

Background I'm new to physics and math. I stopped studying both of them in high-school, and I wish I hadn't. I'm pursuing study in both topics for personal interest. Today, I'm learning about ...
-2
votes
2answers
78 views

Force applied in a body moving at high speed [closed]

Consider a rod of length $l$ and uniform density is moving at high speed. I want to deflect the rod where should I need to apply the minimum force, so that the rod is deflected..?
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vote
2answers
488 views

Forces on a particle moving in a vertical circle

In the diagrma, a particle (A, mass 0.6kg) is moving in a vertical circle. The question is: When it gets to the lowest point, what is the tension in the light rod that is between the center of the ...
0
votes
1answer
5k 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 ...
0
votes
1answer
215 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 ...
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2answers
270 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 ...
4
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3answers
294 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
222 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
381 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
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0answers
49 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 ...
-2
votes
1answer
648 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 ...
3
votes
1answer
564 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
934 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
109 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
733 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
70 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?
2
votes
2answers
3k 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
1k 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 ...
2
votes
1answer
247 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
180 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).
0
votes
1answer
115 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
337 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
4answers
1k 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
193 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
529 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
4k 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
879 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?" ...
0
votes
1answer
180 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
3k 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
1k 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
4k 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
419 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: ...
1
vote
3answers
5k 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 ...
3
votes
2answers
430 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
73 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
390 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 ...
5
votes
2answers
1k 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
419 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
650 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 ...
11
votes
1answer
2k 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
644 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 ...
5
votes
1answer
154 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, ...
-1
votes
1answer
8k views

Conservation of Momentum from Recoil Speed [closed]

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
410 views

Reason behind cohesive and adhesive force

What is the real cause behind the cohesive and adhesive forces?
0
votes
4answers
402 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
149 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 ...