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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1answer
25 views

Normal force and weight

If two books are placed on top of each other on a table, why would it be incorrect to say that the weight on the upper book acts on the lower book? I thought that the weight of the upper book would ...
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2answers
30 views

Trouble understanding non-conservative force and work

I am having some trouble defining whether a force is conservative or not. In the example that we are working on a mass on a pulley system is used to cause a slender bar to rotate from rest to a ...
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1answer
37 views

Question about Thrust; am I correct?

Basically, here's what I understand about Thrust: Thrust is a force. You get it by doing $v\times\frac{dM}{dT}$. Pretty basic, because that's the formula you're given. However, because I'm trying to ...
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2answers
54 views

Centripetal effect or curved space time

I think I understand both the centrepedal effect and Einsteins curved space time. However I am confused about which best describes the motion of a planet ( or other orbiting body ). Simply put, does ...
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0answers
34 views

How to calculate pull force of a solenoid with permanent magnet plunger (NdFeB)?

The solenoid is air core. If we use permanent magnet like NdFeB as a plunger, how to calculate the pull/push force of the solenoid with plunger?
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4answers
3k views

GR and my journey to the centre of the Earth

[General Relativity] basically says that the reason you are sticking to the floor right now is that the shortest distance between today and tomorrow is through the center of the Earth. I love ...
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2answers
58 views

How can you tell if the work done by a force is negative?

This is kind of confusing to me. I'm guessing that it's specific to the problem. Is the work done by friction always negative? Is the work done by gravity always negative? Spring as well? It seems ...
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1answer
40 views

What amount of force could be created by a person “swimming” in air?

Had a question on a physics test, a person is at rest on a frictionless surface and can not throw anything, can they move? I said yes, by "swimming" against the air and got docked because "it wouldn'...
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1answer
30 views

Tensile strength of a chain of electromagnets

I was having a discussion about the tensile strengths of various materials. Could something like a chain of electromagnets be made to have a tensile strength proportional to the power applied to it?
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5answers
110 views

Elevator normal force

In the above case, the normal force exerted by the elevator on the box would be $= 10\mathrm{kg}\ g + 10\mathrm{kg}\ 5\ \mathrm{m/s^2}$, assuming $g = 10\ \mathrm{m/s^2}$, the elevator would exert a ...
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2answers
81 views

How is a mass, suspended vertically by two springs in parallel, kept stable? [closed]

Consider a mass suspended vertically from above by two springs in parallel with different spring constants. Wouldn't the tension be different in each spring? How is this system kept in equilibrium?
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0answers
57 views

Determining the forces required to maintain a static center of mass position; one with velocity and one with acceleration [closed]

I'm having a bit of trouble wrapping my head around this conceptually. The magnitudes and directions of the forces on two of the particles are indicated. What are the magnitude and direction of the ...
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2answers
187 views

What would happen to a motor without a split-ring commutator?

I realise that a similar question has already been asked (Why does the coil in this apparatus reverse its direction of oscillation?), however after reading the answers, I am still unclear on certain ...
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2answers
46 views

Why is Kinetic Energy = (-) Total Energy and Potential Energy = 2 $\times$ Total Energy?

I came across this relation while reading on the Bohr atomic model. Are there any other forces for which these relations hold good?
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1answer
27 views

Does stretching a spring with a relatively high spring constant value require more force because of its inertia?

Other than the fact that a spring has a relatively high spring constant (say 1000 N/m) and therefore requires more force per meter to stretch (not bend or twist).
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1answer
34 views

Rope tension definition

What is the exact definition of the tension of a rope? Here http://web.mit.edu/8.01t/www/materials/modules/chapter08.pdf the following definition is given The tension $T(x)$ in a rope at a ...
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3answers
89 views

Rolling without slipping in absence of friction force

I'm confused about a rolling without slipping situation. Suppose to have a disk of radius $R$ on a floor, and exert a horizontal force at a certain distance $r$ from the center of mass. I would like ...
4
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2answers
152 views

Pressure and weight? (hydrostatic paradox)

Consider two different shaped containers having same area: one is cylinder, the other is like an inverted pyramid (roughly). Both have the same level of water, the weight of the inverted pyramidal ...
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3answers
71 views

According to Newton's third law the force between two object is balanced when they force exert to each other

According to Newton's third law, the javelin exerts as much force on the athlete as the athlete exerts on the javelin. Would it be correct to say that the javelin does work on the athlete?
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1answer
41 views

A conceptual question about work

Consider an object of mass $5kg$ on a plane. If a horizontal force of $10N$ acts on the object for a time interval of a second. Calculate the work done on the object by the force given that the force ...
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1answer
67 views

Force, Mass, Motion? $E = mc^2$

Does any object needs force to move? If 'yes', does the matter needs mass to form a force? These questions arises from me because $E = mc^2$ and $F = ma$ does not relate and one does not agrees with ...
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3answers
69 views

The principle behind Inertia and it's connection to Equilibrium

Inertia is the tendency of a force-free body to remain in that state or it is something that opposes any act of changing its equilibrium state. Mass is a measure of inertia. I have some questions ...
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1answer
22 views

Increasing frictional force without increasing normal force

Is it possible to achieve 10N of frictional force while only having 1N of normal force, using a coefficient of friction no greater than 1? My grade 11 physics teacher is asking us to do this. He ...
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1answer
50 views

Force of baseball bat given force of ball and recoil distance

Say I swing a baseball bat and hit a ball. The ball is moving at 60 miles per hour and impacts the baseball bat squarely at that speed. The ball has moved twenty feet before impacting the bat. The ...
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1answer
39 views

How does distance affect force?

In the image below, the system is in equilibrium. Some force is applied at the bottom of the vertical pole and is being opposed by some force at the top by the horizontal pole... But I feel as though ...
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3answers
77 views

What force prevents particles from penetrating other particles?

I understand that what prevents objects from penetrating each other is the electromagnetic force between the electrons in the respective objects. But if we don't have electrons, for example a proton. ...
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1answer
28 views

Finding the force exerted by a mass at different contact points

Okay so I've been doing a math assignment on torque which has to have real-world applications so I've gone off on a massive tangent trying to incorporate physics principles and trying to get them as ...
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0answers
27 views

Distribution of contact force

Say we have a body resting on a flat surface. The force of gravity acts through the center of mass. The normal force is equal in size and in oposite direction. Since the body is in contact with ground,...
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2answers
66 views

Dynamics of swinging

My husband built a 20'-high tree swing, using 3/16"-welded-link chains to suspend it approximately 2' off of the ground. To our disappointment, pumping barely gets the swing going, with little height ...
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1answer
44 views

Equilibrium of a Solid Body

To find the torques around B, see the figure below, I took the cross product as followed: and we know that $W=160 N$ but when I insert that value into the the equation in the red box, I get $F_3=46....
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0answers
20 views

What is a simple model to find the jump height for the Thomson's Jumping Ring experiment?

I'm trying to devise a basic formula that could give a rough estimate for the jump height reached in the Thomson's Jumping Ring experiment, as detailed here. However, it's pretty difficult as most ...
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0answers
25 views

Detecting force without displacement

I once made a hand strength test, with something that looked like a regular hand trainer, but according the nurse was "mute" (in my language), and then further explained that "it won't move when you ...
2
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1answer
51 views

Contraction of a rotating system

Consider a system of two masses that rotates with constant angular velocity. When a force contracts the system the velocitie of the two masses increase. I understand this in terms of conservation of ...
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3answers
81 views

Zero Potential Energy Change in Raising a Mass

Suppose I am able to lift a body of mass $m$ up using a constant force $F=mg$ so that net acceleration is zero on it. I want to find the potential energy and the total energy of the body when I have ...
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0answers
53 views

Force conversion in a barrel cam-follower mechanism

A barrel cam-follower mechanism consists of a (cylindrical) barrel with a cam track, a cam-follower (roller) inside of the track, a fork connected to the cam-follower and a guide along which the fork ...
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2answers
67 views

Problems with work on an inclined plane

A constant force $F_a$ of magnitude $82.0N$ is applied to a $3.00 kg$ shoe box at angle $53.0^{\circ}$, causing the box to move up a frictionless ramp at constant speed. How much work is done on the ...
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2answers
66 views

How to determine the net velocity change applied by a force vector [closed]

I am a little stumped by the answer of this question. The question reads, "In three situations, a single force acts on a moving particle. Here are the velocities (at that instant) and the forces: ...
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0answers
66 views

Find the tension of rope A immediately after cutting rope B

As shown in the figure, a ball is attached to a ceiling and a wall with massless ropes A and B. Rope A is at angle θ from the vertical direction, and rope B is horizontal. The system is static. If ...
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votes
1answer
210 views

Why it's more difficult to walk in an inclined plane than in a causal road [closed]

my question is about something very casual , but when i tried to solve that , it was not easy at all . My question is : "Why when we walk in an inclined plane we get tired more than when we walk in ...
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2answers
49 views

Question about aircraft/rockets

Lets say that you're sitting an inverted airplane. How do you determine how fast the plane must accelerate in order for you to not fall out?
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0answers
100 views

Shouldn't there be 6 fundamental forces? [closed]

I'm listening to Leonard Susskind's The Black Hole War. In it he states (paraphrased) that a string wrapped around a compact dimension once imparts one unit of charge. Wrapped one way, it's a ...
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2answers
41 views

Why does limiting friction have to act when a block tied to a wall is pulled?

A block lying on a rough surface, is connected to a wall by a mass less, inextensible string and an unknown amount of force is applied to the block opposite to the side of the wall. Now, if it is ...
1
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1answer
43 views

Stuck on a static equilibrium problem [closed]

This is the problem: "The figure below shows a 25-foot sailboat. The mast is a uniform 119-kg pole that is supported on the deck and held fore and aft by wires as shown. The tension in the forestay ...
1
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3answers
63 views

Work energy theorem: variation of kinetic energy as sum of terms given by the work of single forces

Work-energy theorem states that $$W_{\sum F_i}=\Delta K,$$ where I expressed with $W_{\sum F_i}$ the work done by the resultant of forces ${\sum F_i}$ and with $K$ the kinetic energy. In general it ...
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2answers
55 views

Which side of liquid gas interface is at high pressure?

With respect to what(whether liquid or gas) should I consider that the convex side has higher pressure and concave at lower prsseure? As seen in the example of image it is given that air bubble inside ...
0
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1answer
33 views

Some questions about forces

If I am sitting inside a closed sphere (I can't see the outside), can't I feel when the sphere is at constant speed ? Can I feel when it is accelerating ? Why ? The defination of force given ...
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0answers
30 views

Determine what type of force that correspond to a springs-masses system

I am working a question from my Applied Math class, there is a question asked me to determine what kind of force correspond to a springs-masses system. I have two forces, $f_1=1$ and $f_2=-1$, spring ...
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1answer
27 views

Would a bullet damage a piece of metal the same as a pointy stick?

If you used a materials that would offer zero bending or dulling (the bullet/ pointy stick), would a 10 g bullet traveling at 1000 m/s with a surface area of 1 mm squared damage a piece of metal the ...
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0answers
28 views

can different force fields interfere (create interference patterns)

Edit: I have rewritten the question for clarity. I know waves of photons can interfere eachother. What about if you mixed waves of photos with w and z bosons? What about gravitons (if they exist) ...
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3answers
53 views

Pressure or confusion

We all know that pressure is force per unit area. for example we have a pressure of $5N/m^2$, so is the load of $5 N$ acts on the entire area or it acts just at a point i.e. is the load a point load ...