What is Forces: Definition and 1000 Discussions

In physics, a force is any influence that, when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newton (N). Force is represented by the symbol F (formerly P).
The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object.
Concepts related to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object. In an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the internal mechanical stress. Such internal mechanical stresses cause no acceleration of that body as the forces balance one another. Pressure, the distribution of many small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate. Stress usually causes deformation of solid materials, or flow in fluids.

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  1. Parziter

    Solar System Forces -- Simulating the planetary orbits for my project

    TL;DR Summary: Solar sytem forces on Unity Hello ! For my last year in my school, I've got a project to do, and I wanted to recreate the Solar system with forces on Unity. My forces are Velocity and Acceleration (I'm using the Frenet's formulas). I'm sorry I'm not a physicist and that's why...
  2. S

    I Contemplating Gyroscopic Forces for fighting robot weaponry

    The premise is that whenever you watch Battlebots or Robot Wars, there's usually a robot on there which has a vertical drum spinner which weighs half the robots weight and spins at thousands of RPM, and whenever the robot turns, it cocks one wheel in the air due to the gyroscopic forces at play...
  3. MatinSAR

    Forces acting on a block that is pushed against a wall

    Picture of problem: For the object to be moving, it must overcome friction. ##f=0.5*0.6F = 0.3F## ##mg=22N## Upward motion: ##0.8F>mg+f \rightarrow 0.5F>22 \rightarrow F>44N ## Downward motion: ##0.8F+f<mg \rightarrow 1.1F<22 \rightarrow F<20N ## I think correct option is D. Can you please...
  4. Quasar100

    Normal Forces on a Sphere in a Non-vertical Groove

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  5. L

    B If gravity was a force wouldn't going back in time cause us to float?

    This might sound as a dumb and silly question but if you think about it, it makes sense. If we wrongly assume that gravity is a force just like any other, and given the fact that time is closely related to gravity and that gravitational time dilation is a thing, wouldn't reverse time travel...
  6. sHatDowN

    Simple Addition of Vector Forces on an Eye-Hook

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  7. Z

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  8. MatinSAR

    Balance of forces for two charged spheres hanging from the ceiling

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  9. M

    A book rests at an angle against one side of a bookshelf...

    1.52cos(31)+Fbsin(Θb) = (0.305)(9.8) Fbsin(Θb) = 1.69 Now for horizontal direction: Fbcos(Θb) = FLsin(ΘL) cos(Θb) = FLsin(ΘL)/Fb cos(Θb) = (1.52 x sin31)/1.69 cosΘb=0.464 Θb = 62.35 I thought to find Fb I would just plug the Θb value into one of the trig functions, but apparently both of my...
  10. chris25

    Fictitious forces on a rigid body

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  11. L

    B Football padding against forces -- What is the appropriate amount?

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  12. W

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  13. G

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  14. A

    The Work of Friction: Explained in .32m

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  15. F

    I Conservative forces and internal and external forces

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  16. paulimerci

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  17. Clockclocle

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  18. Hadiza

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  19. F

    I Distributed Forces and force density....

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  20. Z

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  21. Ahmed1029

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  22. C

    Is gravity a force or just a consequence of mass?

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  23. J

    I Particle exchange explaining attractive forces

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  24. T

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  25. S

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  26. P

    I Defining the Forces from Magnetic Fields and Electric Fields

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  27. C

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  28. tbn032

    B Unable to understand how these two forces are equal

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  29. Cody Livengood

    B Is there an experiment that shows strong force grows with distance?

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  30. L

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  31. L

    B Do forces of attraction really exist or are they just an illusion?

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  32. F

    I Solving the Block-on-Spring Problem Using Forces

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  33. link223

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  34. A

    I If we take two charges and hold one still, what are the forces?

    If we take two positive charges +q1 and +q2, and we hold q1 still, does q2 experience a repulsive force due to q1 repelling q2 AND a repulsive force due to q2 repelling q1? That is ##|F| = 2*\frac{k*q1*q2}{r^2}##
  35. A

    I My textbook is deriving wave speed on a string under tension

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  36. A

    Engineering Problem with the reaction forces in the gearbox

    Greetings, I have tried to find the reactions of the bearings on the Y direction in the intermediate shaft. but I couldn´t find the numerical results of the solutions here is my attempt: in order to find the forces I did the moment equilibruim around the point A and B With FT1 FT2 and...
  37. G

    What mistake did I make in finding the reaction at hinge A?

    A very simple (I thought!) question: I'm just looking at the first part, finding the reaction at the hinge A. Here is my annotated diagram, with the reaction and A resolved into it's X and Y components, the force at E labelled as Fe and the length of ED labelled as L. Considering the body...
  38. V

    Forces when car wheels "lay rubber"

    Suppose the car is moving to the right, so if the wheels roll without slipping, they are rolling clockwise. To get the wheel to slip, a counterclockwise torque would need to be applied to cause the wheel to have some angular acceleration. If the wheel was slipping, then the bottom of the wheel...
  39. G

    How to find the forces in a particular framework of light rods

    Could I please ask for help in how to do this question. Is it in fact well formed, can it be solved as it is or do I need more information? Q. Find the external forces and the force in each rod in the following framework of light rods which is supported and A and C: So, I need to find Fa...
  40. Finn072

    Shear lines from a FBD with distributed forces

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  41. A

    I Forces to move on the level versus up an inclined plane

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  42. Amphibia

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  43. Y

    Forces applied to a block on a ramp

    hey I am really hope for some help becuase i don't know what I am doing wrong, the angle of the first part is 21.801. here is my solution i would like to know what I am doing wrong
  44. G

    To find the forces acting in a system in equilibrium

    Could I please ask where I have gone wrong with my reasoning in the following question: The answers in given in the book are: (1/2)W tan(Ө) W vertically (1/2)W tan(Ө) horizontally Here is my diagram: Considering the system as a whole: (In the text below "Ya" and "Xa" are the forces at...
  45. B

    B Can You Use a Rubber Bracelet as a Buoyancy Reference for Freediving?

    First of all, I'm new to the forum, and rather uneducated, so I apologize this is likely in the wrong section. I've recently (like last night lol) started looking into freediving. I haven't taken any classes or anything yet, so all of this might be common and answered there. However, one of...
  46. J

    A Generalized Forces and QED/QCD

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  47. S

    Body forces in static equilibrium (FEM issue)

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  48. SpectraPhy09

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  49. runningphysics

    Two forces acting on an object given in vectors - SOLVED

    I tried splitting the forces up into F1 and F2 making Newtons second law equation into F1+F2=ma. Then I added over the the first force given. multiply the mass to the acceleration terms to get F2= (m*ai + m*aj) - F1
  50. M

    I Unbalanced forces acting on a ball at maximum altitude

    When a ball projected vertically upright reaches its maximum height is it instantaneously stationery (calculus provides for instantaneous events) before it starts its downwards journey? is gravity acting on the object at that instant? Newton provides that an object at rest must be subject to...
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