What is Force: 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. LentilSoup7

    Home experiment - 'seeing' magnetic lines of force?

    Thought of doing this one years ago! Basically, I want to 'see' the magnetic force lines that surround a conductor when energized (with an alternating current). I appreciate that what I will see (or at least I am hoping to see) is the pattern formed by the iron dust in response the the field...
  2. E

    How will the equation for gravitational force be changed?

    At first, I thought when the rod goes really far away from the particle, then L would approach to zero in a particle's reference view. As a result, the equation will be GmM/d^2. However, I just thought that L just remain as it is regardless of change in d, but not sure...
  3. A

    Shear Force on Bolts mounting gearbox to engine

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  4. KavaKovala

    Calculate the clamping force to prevent the load from sliding

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  5. Adesh

    How do we provide centripetal force in this situation?

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  6. A

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  7. Achintya

    What is the reality of the Electric Force & Field?

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  8. cwill53

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  9. E

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  10. G

    Determining the power of frictional force

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  11. L

    MHB Force when slipping and falling

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  12. Achintya

    Emergency elevator safety feature calculations

  13. A

    Calculating the normal force with Newton's Laws

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  14. Adesh

    What force will be felt by ##B## when a rod is rotated?

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  15. PCarson85

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  16. PainterGuy

    B Sinusoidal force mechanism for a swing

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  17. Zero

    Calculating the force due to friction

    p man= mv p man = 90 (7) p man= 630 p sled= mv p sled= 100 (0) p sled= 0 p man+sled= 630 + 0 p man+sled= 630 fg man= mg fg man= 90 (9.8) fg man= 882 fg sled= mg fg sled= 100 (9.8) fg sled= 980 fg sled+man= 980+882 fg sled+man= 1862
  18. H

    Horizontal force on glued surfaces

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  19. B

    Electric Force and Field homework problem

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  20. T

    I Exploring Leverage & Force in Exercise Science

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  21. Tony Hau

    Derive the equation of effective force on a rotating frame about Earth

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  22. E

    Friction force of 2 connected block on steel surface

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  23. S

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  24. aspodkfpo

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  25. E

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  26. D

    I How Does Force Distribute Across Protrusions in a Symmetric Object?

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  27. LCSphysicist

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  28. H

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  29. EsinDerin

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  30. S

    Coulomb's Law problem: Force of attraction between the two singly charged ions

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  31. E

    At what range does a conservative force contribute to the thermal U?

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  32. GhostLoveScore

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  33. PickyBiker

    Understanding Force vs Speed for Arduino-Based Inverted Pendulum on Cart

    I am using the Stanford “Dynamics: Inverted pendulum on a cart” document, https://web.stanford.edu/class/me161/documents/InvertedPendulumOnCartSolution.pdf, as the basis for the Arduino c code. I need help with the term Fc (Feedback force on the cart A) because the motor I’m using is a stepper...
  34. McLaren50

    Understanding the deflection of a cable under tension with a force applied in the middle

    With the above in mind, I have a cable of E=60GPa, cross sectional area 7e-4m^2. I want to understand the relationship between the tension applied resisting the deflection of the cable when a force is applied so that the cable will not deflect more than 0.7m in this case. Take the force as...
  35. A

    [Magnetism] Determine the direction of the force experienced by a (+)C

    Given: q = 1.6*10^-19 C B = 0.3 T north v = 3*10^6 m/s north-west θ = 37 (degrees) Solution Attempt: a) F = Bqvsinθ = (0.3)(1.6*10^-19)(3*10^6)(sin(37)) = 8.7*10^-14 N b) Via right hand rule, F is into the page c) a = F/m = 8.7*10^-14/1.6 × 10^−27 = 5.4*10^13 m/s^2 When I checked my answers...
  36. S

    Evanescent and Gradient force on an optical waveguide

    Let's say that on the surface of the cladding we have evanescent field due to the total internal reflection between the core and the cladding. The refractive indices of the the core is 1.45 and the refractive index of the cladding is 1.4, and I want to use the gradient force of the evanescent...
  37. D

    Is my elbow the point of application of force of a torque?

    if i pick up a bucket i apply torque to the bucket. my shoulder is the fulcrum. is my elbow the point of application of force? just trying to understand the physics?
  38. Adesh

    I How a rigid body causes a reaction force?

    The definition of rigid body says it cannot be deformed (theoretically). Now, Newton’s third law is caused (I mean the reaction force is caused ) due to the deformation of the body. What I have learned is that every body is like a spring, when we push on it we compress it and hence feel a...
  39. caesium

    Centripetal force for off-centered cylinders rolling down a curve

    My initial attempt: Total Centripetal force on the cylinder would be given by $$\textbf{F}_{net} = mR\omega^2 \textbf{e}_1+mr_{cm}\omega^2 \textbf{e}_2$$ where the vectors e_1 and e_2 have magnitude 1 and point radially outwards (and continuously changing as the cylinder rolls down) as marked in...
  40. R

    Work Done By a Spring's Restoring Force

    Hello all. Right now I am taking physics 1 and were doing the Work-Kinetic Energy Chapter. I was just reading the derivation for the work done by a spring's force. I understand how to get the result but what i don't understand what to make of it. I understand that because a spring's force...
  41. M

    Force between two neodymium permanent magnets

    So I was wondering how I calculate the magnetic force between two magnets. When we learned about magnets, we only covered magnetic fields and electricity (laplace's law) and how electricity can create a B-Field. But how will two B-fields (or magnets) affect each other? Is there a simple formula...
  42. S

    I Calculating force when landing on a beam

    I am designing a machine at the moment, and I am struggling to get my head around impact forces. I have established that the force applied is mgh/d, but I am struggling to work out the value for d. Taking it in isolation, assuming that the falling weight does not "give" in any significant way...
  43. H

    Question on pulleys force and rope pulling

    I have a question about the following 33 and 34. For number 33 I think the answer is B because you have to life up against the force of gravity. While with A you have gravity helping you out. The correct answer is A but I am not sure how. for 34 I think B because you have an extra pulley so...
  44. E

    Electromotive force (or E cell?) during charging and discharging

    The EMF of the cell is the potential of the cathode subtract that of the anode, consistent with ##\Delta G = -nF\varepsilon##. If the cell is running as a galvanic cell/discharging, the EMF should be positive. If it is charging, the cathode (the one gaining electrons) is now negative and at...
  45. naushaan

    Calculatingthe resultant gravitational force on spherical objects

  46. R

    Maximizing Repulsive Force with an Electromagnet

    Hi all. New to the forum and new to making electromagnets. I want to pick your brains as I know extremely little about electromagnets. So I have a 2 1/2 inch round x 1 inch thick rare Earth magnet that I’m trying to repel with force using an electro magnet. The repel would be in bursts. I know...
  47. K

    Is non-linear Tension Force possible?

    I seem to remember from my school days that Tension Force can only be linear. Is this true? In 1 (in the graphic) the tension will follow the line of the rope In 2 there is an unbendable, unbreakable, steel cable formed into an arch. a ] In 3 which direction will the Tension be? b ] In 3 if...
  48. J

    Designing Impact Force Test Rig for Material Strength Testing

    Hi all, I have just started work experience at an engineering company in the design department. I've be tasked to develop a test rig, Similar to a charpy rig. Intended to measure the impact strength of materials. The design will consist of an A-frame structure with swing arm attached to the...
  49. K

    I Horizontal Tension Force equation

    (not a homework question - I left education over 45 years ago) Hi, this just out of interest as I have been googleing this and can't find the answer I know the equation for tension force, for example a weight on a string, block on a ramp, etc. But is there something similar for a horizontal...
  50. SpaceThoughts

    Velocity calculation of an accelerated mass based on an increasing force

    A known force is doubling (egal) over a known distance, accelerating a mass. How do I calculate the final velocity of the mass at the end of the known distance , when the mass has doubled? I don't know the time. The mass is accelerated from 0 meter and from 0 velocity.
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