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. A

    Coriolis Force and Centrifugal Force

    Hello! So for a) I have done the following m = 400t = 400000 kg v = 300 km/h = 83,3 m/s ##\alpha## = 50 (degrees) Now this is the formula for the Coriollis effect $$ F = 2 \cdot m (v × \omega) $$ So in a book I found in the library regarding physics I've found a similar example that used...
  2. S

    What is the maximum frictional force?

    In the attachment I am supposed to calculate the maximum frictional force of a block on a 35 degree angle incline (that is the point at which the force acting opposite frictional force is highest) I make it out to be sin(35)*120N = 69N but the book says 675N and it gives it as...
  3. W

    [Statics] Determining the normal force at an internal point of a member

    For this problem (see image), I get the correct answer for the normal force at point E if I: 1) divide the frame into members AB and CB, 2) solve for the x and y components of the reaction force at point B, 3) make a free body diagram with the cut at point E forming member EB and setting the sum...
  4. C

    Is the Braking Force of a Truck Really 0.8?

    Hi guys I'm a truck driver. Not sure if I'm posting in the right place so i apologise. Iv'e been on a course today about trucks. The course leader was talking about forces. A trucks force forwards can be 0.8. Is this true?
  5. greg_rack

    Best straightforward method to calculate the direction of the Lorentz force

    Hi guys, I'm being introduced to magnetism, and the direction of the Lorentz force is quite confusing since it's involving a vector product. Which method would you recommend me in order to easily deduce the direction?
  6. Amrator

    Relativity: Force and a Collision

    I don't know if I did this correctly. ##\int Fdx = \int dE## ##F \Delta x = \Delta E## ##Fx = Mc^2 - (mc^2 + mc^2)## ##M = \frac{Fx + 2mc^2}{c^2}## ##M## is the mass of the resulting particle. ##2mc^2## is the total energy before the collision. The issue is I'm assuming that the resulting...
  7. TonyCross

    Calculating Theoretical Reaction Force of Ball Traveling in Semi-Circle

    Summary:: Theoretical reaction force due to ball traveling in a semi-circle circum Hi, Can anyone please help me with the following question: Setup... 1 x length of pipe bent 180 degrees with an inner diameter of 22mm, it's radius is 2mtrs, the mass of this object is 100kg. Total length of...
  8. Andrei0408

    Expression of the force derived from this potential

    I just don't know what equations I should use, or what exactly I need to do. I just need some guidelines, thank you!
  9. N

    What is the Relationship Between Force and Weight?

    So here's what I've tried: force from part (a) / weight = 499.649N / 15kg = 33.310 force from part (b) / weight = 10.511N / 15kg = 0.701 Apparently this wasn't correct. What am I doing wrong? I feel like I'm missing the obvious.
  10. SamRoss

    Magnetic attraction / repulsion from the Lorentz force

    I'm trying to understand how the Lorentz force can explain why magnets attract and repel. The explanations that I have found have mostly involved the magnets moving in a way that decreases the forces between them ( ) but I have not been able to find any intuitive explanation involving the...
  11. P

    I Finding the Velocity of an object due to an imparted force

    Hello folks, I was wondering how I could calculate/find the velocity of an object from an imparted force given its mass. My force is 26 MN, the object is 10 metric tons, or 10kKg, what will the objects velocity be if this force was applied to it rapidly, e.g. like a jab/punch. My goal is to...
  12. L

    Engineering Cantilever and encastré beams: bending moment and shear force

    I have to discuss the Bending moment and shear forces in cantilever and encastré beams. Does anybody know of good websites showing that is simple to understand showing. All i can find is how to calculate and bending moments and shear force digrams which don't really understand. Can...
  13. L

    Engineering Bending motion and shear force

    A cantilever beam 2 meter in length, 5KN act at point (A) of the beam. There is point x it looks like half way along the beam. how do i workout the distance of point X so work out the magnidues of Ra and Rb so i can go onto working out bending motion and shear force?ruff idea i had 1) Ra x 2...
  14. F

    I Special Relativity & Non-Instantaneous Force Equations

    In classical mechanics, the gravitational force is described by the equation: F = Gm1m2/r^2 What would this equation - or other similar equations - look like in special relativity? This equation cannot be correct because it implies that the force acts instantaneously.
  15. Mr_Allod

    Understanding the Force on a Magnetic Dipole in Different Orientations

    Hi there, I approached this problem by making use of the fact that a dipole can be modeled as a small current loop with the magnetic field ##\vec B_1 = \mu_0 \frac {m_1}{4\pi r^2} (2\cos \theta \hat r + \sin \theta \hat \theta)## which is the far-field approximation for a regular circular...
  16. P

    Finding Force and Energy from an indentation into a volume

    Hello folks, a recent theoretical discussion with a materials engineer has left my head spinning, this sort of thing is beyond me but I am curious if any of the clever folks on here could solve my problem. I want to find the Force and Energy applied by my Indenter within the following...
  17. K

    Understanding of Wave swing physics

    Yeah, as I said, i have no idea why we can assume beta to be the same for any position at given alpha.
  18. B

    Is friction really always related to the normal force?

    What I know is that the force of friction and the normal force are the components of a contact force. So force of friction is related to the contact force. Friction is also related to the normal force by equation ##F_t= μ\cdot N##. In this case (because the block is not moving) N=0 and...
  19. andyonassis

    Gyroscope (Coriolis Torque and Force)

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  20. Caw

    Centripetal force problem involving a washing machine

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  21. archaic

    Cylinder rolling due to magnetic force

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  22. shk

    Force and motion -- A water drop on the windscreen of a car

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  23. K

    Selection of a compression spring

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  24. Hamiltonian

    Doubt related to buoyant force and fluid thrust force

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  25. Ntip

    Force on conductors during a short circuit fault

    If I have two parallel bars serving as a DC bus with a capacitor across the output and there is a short fault event, I know the peak current is limited by V/X. The instantaneous current would be a function of the time RLC time constant. How do I relate this to the force on the conductors due to...
  26. SamRoss

    I How is the weak force related to a change in velocity?

    Hi everyone, The four fundamental forces are gravity (I understand that G.R. does not look upon gravity as a force but I'm not worried about that here), the Lorentz force, the weak force, and the strong force. I'm familiar with the inverse square law for gravitation and the Lorentz force...
  27. S

    Why is the Force on the Wire Directed from Stronger to Weaker Field?

    I understand how the weaker and stronger field occurs but I don't understand why the force on the wire is directed from stronger to weaker field. I mean why not from weaker to stronger? I also want to ask about Newton's 3rd law in this case. Newton's 3rd law states that for every action there...
  28. B

    Net force acting on a ping-pong ball

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  29. rbmartel

    I Which area should I use to calculate the force on a submerged surface?

    Let's say we have a tank filled with water only half way up. I want to calculate the force being applied by the liquid on one of the walls, that's F = P.A. For the area (A), should I consider the area of the entire wall (H.L), or only the area of the wall that's in contact with the liquid...
  30. shivam2571

    Torque and Force question -- Multipe forces acting on an object

    I have attempted and got 2 different solution 1: 2:
  31. LuisBabboni

    I Why is the weak force a force?

    Hi! I could understand gravitational force as a force that move mass. I could understand electromagnetic force as a force that moves chaerged particles. I even could understand strong force as a force that atrack protons I could not understand the moment of what weak force changes. The moment...
  32. T

    Quadratic Drag Force: Solving Differently

    But the answers to these two questions confuses me. For the first question the answer goes like: $$m\ddot y = -mkv^2-mg$$ $$\therefore \ddot y = v\frac{dv}{dy}$$ $$\therefore v\frac{dv}{dy}= -kv^2-g$$ but for the answer to the second question we have: $$m\dot v = mg - cv^2.$$ Both questions...
  33. M

    B Mass of Hanging Rope: Calculate Easily

    Hi, I have a question about a hanging rope - how do you find it's mass? I've been searching a long time, stumbled across some advanced calculus involving catenary functions and equations, but couldn't quite figure it out.
  34. J

    Direction of the Coriolis force

    How can I determine direction of Coriolis force for these cases?1)Ship travel at 45th north parallel to the east (course 90°)2)Ship travel at north hemisphere at course 45°3)Ship travel at equator at east (course 90°) My attempt: 1) Coriolis force is point up,vertical to the Earth surface 2)I...
  35. S

    Determining net force and acceleration

    Hi All, Please see attached photo of the question. It is asking for net force and acceleration. Taking the forces acting upwards and downwards on the parachutist as vectors: for A the net force would be 800-300=500; B would be 0 and C; would that be 800-1500=-700? And if so would that imply...
  36. Feodalherren

    Torque to force conversion (from a motor)

    So this is a silly problem that I ran into at work which made me realize that I have all but forgotten Newton's laws of motion after years of working with just hardware and software. I am in the middle of programming a robot for an industrial application and I realized that I have no clue how...
  37. G

    Force in the legs of a hexagonal table

    We know that the net force on the table must be zero $$\sum F_i = F$$ We know that the components of the torque with respect to the origin is also 0. $$\sum \tau_x = 0$$ $$\sum \tau_y = 0$$ $$\sum \tau_z = 0$$ But the problem becomes insufficiently constrained that there are only 4 equations...
  38. B

    Finding the resultant force using a vector polygon diagram

    Hi I made an attempt at this problem but have got the wrong answer The correct answer is actually resultant force = 21.767 N at 61.34 degrees (or 151.34 degrees bearing), but I don't know how they got that? Any help would be appreciated! Thanks
  39. anonymous99

    How Does Deformation Affect the Net Force Between Two Masses?

    S
  40. robotman

    Potential Energy associated with a Variable Force

    Don't really know what they want from me
  41. R

    Electromotive Force, Batteries, Resistors, and Potential Differences

    I have attached a small excerpt from my digital book where they start talking about emf. I am very confused. Let me explain what is confusing to me so that you can clear up what's bothering me. They start of by saying that an emf device pumps charges by maintaining a potential difference...
  42. N

    Analyzing Velocity and Force of a Chain in Motion

    My solution: For the horizontal portion of the chain: let at any instant the length of chain inside the tube is x, and at that instant the chain in the tube is having a velocity v. Then, at any instant: ##F = \frac{\mathrm{d} p}{\mathrm{d} t}## ##p##= mass of the chain in the tube at the...
  43. person123

    Inertial Force in Fluid Mechanics

    According to one explanation, the left hand acceleration terms of Navier Stokes equations are the called the inertial terms. If you were to balance forces on the fluid particle, they would have to be equal and opposite to the forces on the right hand side (pressure gradient, viscous, and body)...
  44. T

    Help with centripetal force and friction question please

    Ff = Fc (mv^2)/r = kmg (v^2)/r = kg v^2 = kgr v^2 = 0.7*9.8*200 v = 37.04 m/s I chose option e, and its wrong. What am i doing wrong here?
  45. E

    Net electric force of multiple charged particles in 3-d space

    I draw the graph like this: For (b), I divided each force vector to e from p1 and p2 as x and y parts. I computed them and got Fx=-4.608*10^(-15)N Fy=-2.52*10^(-15)N However, I am not sure whether I did it correctly or not... I appreciate every help from all of you! Thank you!
  46. P

    Direction of force on a voice coil

    I want to understand the direction of force on the voice coil, if the conductor is straight line it is easy to find the force direction. In the case of the diagram i shown below, for the curved surfaces i should take tangential to the surface at every point. Am i correct? So for position 1 since...
  47. C

    How far can the person climb up the ladder before it starts sliding?

    Look on picture two for my equations, I’m pretty sure my first three equations are correct as it’s the same on the answer paper I got. Answer paper only shows the three equations and correct answer so I have no idea how they got to it. When I put the equations togheter And solve out ”h” i get...
  48. M

    "KICK" force exerted from a hydraulic cylinder

    Hello,I am building a press that will squeeze hot steel ,back off .5"push hot steel in further and repeat.The cylinder is 4" bore , 1.375"rod and travel is 8" (the majority of squeeze will be at 5"of extension)at a max of 2500PSI. my question is when putting @15 tons straight down what will the...
  49. E

    Does the electrostatic force create current in the circuit?

    As I understand potential difference is the reason of current. Does it mean that the electrostatic force creates current?
  50. goodOrBad

    Block A Reaches Equilibrium: 92N Force

    I tried to solve it via equilibrium equations and I got 92N for block A
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