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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4
votes
1answer
194 views

How is weight distributed when legs are astride?

Is there a simple and quick formula to find the weight (the force acting) on each leg, especially when legs are astride and they are not equally stretched? (or, better) not equally distant from the ...
0
votes
1answer
409 views

Why does the co-efficent of kinetic friction of a block on an inclined plane not change when you increase the angle of the plane?

The coefficient of kinetic friction can be calculated using $\mu_k = F_k/F_n$. A change in angle does not affect the normal force, but doesn't a change in angle affect the friction? As in if the angle ...
2
votes
1answer
42 views

How is dark matter meant to explain the faster than expected rotation of galaxies? [duplicate]

The stars on the outer edges of galaxies go around faster than they should be. How is dark matter meant to account for this? if you just add more mass wont that just give it a greater gravitational ...
1
vote
1answer
73 views

Calculate direction vector given start-end positions and velocity?

I'm trying for a week now and I really have a hard time with this one. I'm pretty sure that this is something very simple but I can't seem to find a solution. I'm making a game where the enemy is ...
1
vote
1answer
49 views

Electric force between charges in two different media

As far as I know, Coulomb's law of electrostatic force is applicable on two different charges situated in same medium. But if two individual charges are in different media (say one charge on a iron ...
0
votes
1answer
30 views

Finding directions of the internal forces within a freely jointed rigid object?

Consider the the following problem: Here is a force diagram showing the situation: For part (i) Taking moments about $B$ for $BC$ gives $84.5Lcos\beta=2LT$ So $T=39$N For part (ii) Resolving ...
0
votes
2answers
144 views

Advantages/Disadvantages of “hanging off” a motorcycle when leaning

The closest question I could find with regards to this subject was this one: Countersteering a motorcycle However, it does not address the specific physics of what I would like to know. There are 3 ...
1
vote
1answer
530 views

Derivation of formula of potential energy by a conservative force [duplicate]

the formula for potential energy by a conservative force is given by: $$ F = -\nabla U(r), $$ which in one dimension may be simplified to: $$ F = -\frac{dU}{dx} .$$ My question is how is it ...
4
votes
1answer
35 views

Determining average number of fragments created upon explosion

Suppose you're analyzing some 3 dimensional object of any sort of shape, and this object explodes from some internal force (e.g, like a grenade). How would you go about determining the average number ...
0
votes
1answer
113 views

How to compute speed without knowing mass or charge values?

A gold nucleus is $460$ fm ($1$ $fm = 10^{(-15)} m$) from a proton, which initially is at rest. When the proton is released, it speeds away because of the repulsion that it experiences due to the ...
18
votes
6answers
3k views

The best way in which a man can pull a train

I have chosen this example as a paradoxical limit, but my question really regards the optimization, distribution and outcome of force when you try to pull a weight: how can you optimize your ...
0
votes
2answers
59 views

Calories Burned While Hiking [closed]

I want to find out how many calories are burned on any particular hike by any particular by using a formula. I figure it's probably a simple physics question, but since I never took physics, I don't ...
1
vote
2answers
46 views

Force on every particle?

Say there is a horizontal rod, where a force $P$ is applied to the right hand side of the rod to drag it horizontally to the right. If I drew a force diagram, I'd put some vector with a length of $\| ...
0
votes
1answer
193 views

Calculating Resultant Force and Torque

I'm working on a sandbox game that allows the player to build a spacecraft and attach thrusters in arbitrary locations on the hull of the spacecraft. The game is set completely in 2D. (I'm a ...
0
votes
2answers
105 views

Why doesn't a car slide down a banked road when there is no friction?

In case of banked roads without friction, there is an additional $mg \sin(\theta)$ which is unbalanced. Why isn't this taken into account because it is responsible for making the vehicle slide down ...
1
vote
1answer
112 views

Forces acting on a double pulley

In a double pulley system, if the mass of the object is 10 kg and the object is accelerating upwards at 2 m/s$^2$, what is the tension in the ropes? I figured the weight of the box is 100N and the ...
4
votes
5answers
2k views

Will gravity pull together two bodies from the other side of an empty universe?

Lets say that there are only two bodies in the universe, 65 kg each. Other than that the universe is completely empty, no neutrons, no photons, no dark energy/matter, not even neutrinos (that is to ...
1
vote
1answer
34 views

Pseudoforce and friction: confusion

Consider the following situation. A block of mass $M$ is resting on a rough horizontal ground, and a frame is moving towards the right horizontally with an acceleration $a$. Suppose the coefficient of ...
0
votes
0answers
206 views

Solenoid pull force & Velocity calculation

So I am building a circular accelerator (like a slightly oversimplified model version of CERN) as a physics project, and I'm at a dead end. I believe I need to know how to work out differential ...
0
votes
2answers
92 views

Does the coefficient of restitution matter in a collision?

Suppose two particles are colliding. Let initial velocities be $u_1$ and $u_2$ .Their final velocities are $v_1$ and $v_2$. Now $u_1$ and $u_2$ are known. By intuition I can understand that $v_1$ and ...
0
votes
1answer
231 views

A moving inclined plane with block problem

I'm trying to solve for a challenging problem : a moving inclined plane with a block I want to solve for the acceleration components for the block and the plane and the normal force acting on the ...
5
votes
2answers
455 views

The acceleration vector of a simple pendulum

In this picture the acceleration vector $\vec{a}$ points upward when the pendulum is halfway Click To see animated GIF But according to this picture, the force acts tangentially: Which means the ...
3
votes
1answer
122 views

Forces acting on two balls in a jar [closed]

Consider the following situation: Two balls are inside a jar with diameter $D$. The balls are uniform in mass and both have the same diameter $d$. Express the forces that acts at the colored dots ...
0
votes
5answers
268 views

Who does work while walking?

While walking the work done by friction is zero. But who does the work, actually? How someone is getting displaced? This situation also arises when someone climbs without slipping or is climbing a ...
1
vote
4answers
108 views

Since everything with mass exerts a gravity force on everything else, why do objects float in outer space?

For example, if you were to go out into deep space, and just slow down and stop your rocket. Everything inside the rocket that's not strapped in, starts floating. Why is that if every object has mass ...
0
votes
2answers
128 views

Why is there a static frictional force on an object that rolls without slipping?

It is clear that if a frictional force must exist on an object that rolls without slipping, it must a static frictional force because the contact point of the object with the ground does not move. I ...
7
votes
2answers
1k views

Which force is responsible for victory in tug of war?

I'm confused: In a tug of war game on rough ground who will win? The one who applies greater force on the rope or the one who applies greater force on ground?
0
votes
2answers
78 views

Penetration of a bullet into a wall

In which of the following situation will the bullet of the pistol penetrate deeper in the wall? Why? Alternatively will the penetration in both cases be the same? Can you explain the concepts behind ...
4
votes
3answers
103 views

Foucault pendulum initial velocity

This is a basic question I can't solve and it seems it is not addressed on the web. Sorry for my lame painting skills. Assume we have a foucault pendulum suspended in the north pole. the pivot is ...
2
votes
1answer
36 views

Computationally solving bodies that push and pull

Is there a way to find a solution for the positions (as a function of time) of multiple free bodies that push and pull on each other? Say for instance I have a collection of cells which can ...
12
votes
7answers
2k views

Why do we fall down when the bicycle slows down? [duplicate]

My question is: It is easy to balance a bicycle when it is moving at a fairly high velocity, say 7 m/s or 25 km/hr. But when a bicycle slows down, it is hard to keep it upright, and the person riding ...
1
vote
2answers
284 views

Force Diagram for K&K 2.13 [closed]

I have been (independently) working on Problem 2.13 in Kleppner and Kolenkow's An Introduction to Mechanics and come to an answer which conflicts with the hint the authors provided in the book. The ...
1
vote
2answers
129 views

Gravity on a upward moving object

I know I should have listened to my teacher in physics class but I didn't. I need help on a thing I am trying to do for a game. I want to be able to calculate Gravity pushing down on a object over a ...
3
votes
5answers
301 views

Forces as vectors in Newtonian mechanics

I seem to be confused about the nature of forces as vectors, in the basic Newtonian mechanics framework. I know what a vector is as a mathematical object, an element of $R^3$. I understand that if a ...
2
votes
2answers
146 views

Power to suspend a mass in air

How much power is needed to suspend a mass in the air? The four parts below deal with the same problem. I post them all here, should there be some subtle things I didn't see. The textbook problem A ...
0
votes
1answer
46 views

Determining the moment of force [closed]

A force $F = 3i + 2j$ passes through through a point $P$ with respect to an origin $O$. How do I determine the moment of the force at the origin.
0
votes
1answer
216 views

How to calculate the supporting force exerted by a stationary object (cupboard) and support (brackets) for it?

I have a wall mounted Stuva Ikea cupboard, which measures 60x64x30cm. The base is 64x30cm. It is already supported by 2 holes at the back base, (64x60cm). But I need to add in L shape brackets ...
1
vote
1answer
361 views

How does static friction increase with increase in the applied force?

My book says that 'Between surface of contact between two bodies there are contact forces applied between each other (they are equal in magnitude but opposite in direction,obeying Newton's 3rd law) ...
0
votes
1answer
62 views

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 ...
0
votes
0answers
46 views

Interaction Between Two Bar Magnets

How would one describe the interaction between two bar magnets? In the E&M course I took we described quite a few very basic electric interactions, but things that I would have thought of as being ...
2
votes
0answers
69 views

Magnetic Force on a Ferromagenetic Material

I am currently working on a project involving solenoids, and I needed a force(Newtons, not a measure of magnetic field strength) equation. What I came up with after some digging around on the ...
1
vote
3answers
99 views

Confusion relating the application of Work-Energy theorem

Could someone kindly explain the solution to my confusion? When we walk at a constant speed up a steep hill, is work being done? Then why isn't our kinetic energy changing as work done is equal to ...
1
vote
1answer
68 views

Pushing a crate on a friction floor [closed]

A man is pushing a crate at a constant velocity. there is a friction between the floor and the crate of $$\mu =0.41.$$ The pushing force is directed downward at an angle $\theta $ below the ...
15
votes
3answers
2k views

Explanation for this type of (magic-trick) suspension? [closed]

Well let's start off with that I'm not a physicist but I'd like some thoughts on something I came across in my hometown. This guy: Is it possible that due to the electrical charge of magnets this ...
0
votes
1answer
48 views

What physical forces allows for electromagnetic induction

In electromagnetic induction, what force is actually doing the work? what physical force actually drives the electrons around the circuit? Let's say we have a coil and an increasing magnetic field ...
0
votes
1answer
109 views

Work done by Internal Forces

Why is it that internal forces do not change the potential energy of the system? Assume that a man stands on earth with a dumbell. If the dumbell is the system, when it is raised a height h, the work ...
2
votes
1answer
41 views

Eddy Currents: Relationships between thickness and deceleration

This is probably a question with a very simple answer, but I want to make sure before I write too much. I'm doing an investigation on Electromagnetic fields, in particular eddy currents and how they ...
0
votes
1answer
36 views

When the magnetic force is perpendicular to the velocity what will be affected on a charge? [closed]

I guess it can also be stated as a two part question. Is the velocity of a charge always perpendicular to the magnetic force, and when the magnetic force is perpendicular to the velocity what is ...
11
votes
4answers
305 views

Is force a contravariant vector or a covariant vector (or either)?

I don't understand whether something physical, like velocity for example, has a single correct classification as either a contravariant vector or a covariant vector. I have seen texts indicate that ...
1
vote
2answers
69 views

Finding coefficient of friction between block and plane [closed]

An inclined plane makes angle $\theta$ with horizontal. Upper half plane is perfectly smooth where as lower half is rough. The block of mass m starts sliding from top. If the block again comes to rest ...