Normal force Definition and 471 Threads

In mechanics, the normal force




F

n





{\displaystyle F_{n}\ }
is the component of a contact force that is perpendicular to the surface that an object contacts, as in Figure 1. In this instance normal is used in the geometric sense and means perpendicular, as opposed to the common language use of normal meaning "ordinary" or "expected". A person standing still on a platform is acted upon by gravity, which would pull them down towards the Earth's core unless there were a countervailing force from the resistance of the platform's molecules, a force which is named the "normal force".
The normal force is one type of ground reaction force. If the person stands on a slope and does not sink into the ground or slide downhill, the total ground reaction force can be divided into two components: a normal force perpendicular to the ground and a frictional force parallel to the ground. In another common situation, if an object hits a surface with some speed, and the surface can withstand the impact, the normal force provides for a rapid deceleration, which will depend on the flexibility of the surface and the object.

View More On Wikipedia.org
Recent contents Top users
  1. G

    Question about Normal Force and Torque

    Homework Statement A block of uniform density experiences a force F to the right, applied 5/3 m from the bottom of the block. The block is 2 m high and 1 m wide. Take the pivot point to be the point at the bottom right of the block. Find the value of the force that is just able to tip the box...
  2. SirMarx01

    Automotive What is the compression force of a ring seated inside a cylinder

    Hello. I am finding out how many normal force between ring and cylinder. I try to find around for many hours but get noting. there are 8.2 mm inner diameters than put in 8.6 mm cylinder. The hardness of sealing element is 55 ShA. Contact area is 48.63 mm^2. I have data and drawing in attachment...
  3. Beth N

    Circular motion: normal force on a loop

    Homework Statement A 180lb pilot flies a verticle loop with radius 2000 ft at 350 mi/h. With what force does the seat fress upward against him at the bottom of the loop? Problem 6.21 Homework Equations ##F=ma## ##F_c=\frac {mv^2} {r} ## The Attempt at a Solution There seems to be a...
  4. W

    My Second Post: Change in Magnitude of Normal Force?

    Hello, Let us imagine a solid immersed in a liquid in a container such that the density of the liquid is less than the density of the solid. This means that the solid must sink. Let us study the solid when it reaches the bottom surface and is now at rest. The forces acting on the solid when it...
  5. U

    B Where's the action force if the normal force is a reaction force?

    I know that normal force is not a reaction force to the gravitational force; - First, because the gravitational force is from Earth on the object (action force) thus the reaction of force is simply form the object on Earth according to Newton's third law. - Also because in certain situations...
  6. SmamMir

    System of equilibrium, why won't the normal force apply?

    Homework Statement Homework EquationsThe Attempt at a Solution I've resolved all the relevant forces (tension, weight, normal force), but upon looking at the mark scheme, there is no normal force to be resolved. Forgive me if I'm missing out on something obvious, but shouldn't there be a...
  7. isukatphysics69

    Normal force between ball and cone?

    Homework Statement Homework Equations f=ma v^2/r The Attempt at a Solution ∑FX= FN ∑Fy= -mg We are not given an angle, i would have put FNcos(θ). I have my radius as 0.25 by relation of the triangles at that point of the height being .50m so ∑FX= FN = v^2/r = (1.2)^2/.25 = 6.25N
  8. J

    Normal Force: Inclined Plane vs. Banked Turn

    I"m wondering, at the abstract level, why different mathematics is used to calculate the Normal Force in an inclined plane versus a banked turn (which a vehicle is driving around). For an inclined plane, the standard approach is take weight and resolved into parallel and perpendicular vectors...
  9. Liam C

    Coefficient of Friction when Normal Force is Reduced [HS]

    Homework Statement A 5.0kg block of wood sits on a table with a string running over a pulley suspending a mass. The largest mass that can be suspended without moving the block of wood is 0.75kg. a) Calculate the coefficient of friction in this case. b) What type of coefficient of friction has...
  10. Johns24

    Normal force of a block with a massless rope

    Homework Statement Mass of block: 19kg Applied force: 225N at 16 degrees to accelerate block from rest Coefficient of static: 0.55 Coefficient of kinetic: 0.30Homework Equations Unknown The Attempt at a Solution I have solved for parallel tension and perpendicular tension Tperp =...
  11. N

    Static friction confusion -- Friction versus the Normal force

    I am a bit confused. We have an inclined plane. So I know that Ffmax=μ*N and μ is the coefficient of friction calculated as tgθ (θ is the angle at which the body is on the verge of sliding) and also Ff<=Ffmax And we know that the force that makes the body slide is mgsinθ. So as the angle...
  12. E

    A frictionless incline with a block sliding down it....

    A frictionless incline (the triangle below) is bolted to the floor so that it can not move. A block of mass m slides down the slope, which makes an angle with the horizontal.a)Draw a free-body diagram for the block, labeling all forces uniquely. b)Describe all the forces listed above in the...
  13. M

    How do you find the normal force of an object being pushed?

    Homework Statement A 42 kg wagon is being pushed with a metal rod that makes an angle of 46 with the horizontal. The applied force is 449 N and the coefficient of kinetic friction between the wagon and the ground is 0.21. I'm not sure what equation to use to find the normal force and then the...
  14. E

    Torque on Rod Due to Normal Force at a Hinge

    Homework Statement In this diagram, I wondered if there is any torque due to the normal force from the hinge, once the support stick is removed. I also want to know what the normal force would be at the hinge. The cup and ball are to be ignored here (essentially massless). Homework Equations...
  15. Luxucs

    Normal force as a function of time (oscillator)

    Homework Statement A spring with spring constant k is attached to a box of mass M in which is placed a small body of mass m. The system is displaced a distance A from equilibrium and released from rest. Find the normal force between the box and the small mass as a function of time. For what...
  16. N

    How do I calculate the normal force for equilibrium lab?

    I did torque and equilibrium lab report, where I had to hang some weights on a meter stick, which was placed on a fulcrum. There were 3 parts for the lab, with different settings. I am stuck at the last part, where I hang the meter stick with a string over a pulley, and there were 4 weights...
  17. M

    Normal force for stacked objects in a moving elevator

    Homework Statement Say I have two objects on top of each other in an elevator (say Object 1 on the bottom and Object 2 on top), each with a given mass. The elevator is accelerating downward (meaning the elevator is moving up and slowing down). What would the normal force be on Object 1...
  18. R

    Do I need to consider normal force when sliding down a pole

    If someone was sliding down a vertical pole (like a firefighter) would only friction need to be considered to find out how fast the person is "falling" or is there also normal force from where the person is touching the pole, and would that affect the person's speed down? (I am ignoring air...
  19. M

    Impulse Problem- time-average of normal force when running

    1. The problem statement, all variables, and given/known data A somewhat paraphrased version of the problem: Consider the vertical motion of the center of mass of a 150 lbs person as they run along a track. Suppose the person's cadence is 4 steps per second, and with every stride, they briefly...
  20. L

    Newton's third law - normal force

    Homework Statement A book is placed on a chair which is standing on the floor. An iPad is placed on the book. The floor exerts a significant force: A) only on the book B) Upwards on chair and downwards on book C) ONLY upwards on chair D) upwards on chair book and iPad E) downwards on...
  21. B

    Help with finding Normal Force of inclined plane

    So this is the problem: A 250-kg crate is on a rough ramp, inclined at 30° above the horizontal. The coefficient of kinetic friction between the crate and ramp is 0.22. A horizontal force of 5000 N is applied to the crate, pushing it up the ramp. What is the acceleration of the crate? Relevant...
  22. B

    Forces on a plane exerted by a ball

    Could someone please provide a diagram of all the forces acting on the plane, and explain why the answer is E? This is from the 2014 F=MA exam. Thanks, blueblast
  23. IntegralBeing

    I Does the normal force really equal mg on earth? I think not....

    Dear community, I am very ashamed to have not noticed this result but well into my physics major, and I would like to share it with you. I am not sure it is right, which is my reason for posting it. The normal force is classically referred as...
  24. A

    B Can the normal force be in vertical direction?

    HI, Can the normal force be in vertical direction ?
  25. Rotnort

    Magnitude of Frictional Force in Simple Harmonic Motion

    Homework Statement I do not fully grasp the concept behind all of these sub questions (i)-(iv). Homework Equations v=wAcos(wt) (SMH)? Friction Force = Coefficient of Friction * Normal Force The Attempt at a Solution (i) Varying as simple harmonic motion sees varying acceleration as it...
  26. F

    Direction of Normal Force on Object B: A Scientific Inquiry

    Homework Statement The Attempt at a Solution Can somebody please assist me in finding the direction of the normal force exerted on B? (How is normal force at B also normal to the rod? ) There is no hint provided from which I can conclude the direction of normal force. Can somebody please...
  27. EastWindBreaks

    Normal force in a curvilnear motion

    Homework Statement The system shown is initially at rest when the bent bar starts to rotate about the vertical axis AB with constant angular acceleration a 0 = 3 rad/ s2 . The coefficient of static friction between the collar of mass m = 2 kg and the bent bar is f.Ls = 0.35, and the collar is...
  28. T

    Elevator Problem: What is the Normal Force Acting on a Person?

    Homework Statement A 74.0 kg person is standing inside an elevator. The elevator is moving from the 3rd floor to the 21st floor. As the elevator passes the 4th floor it is moving at 2.30 m/s and is increasing speed at a rate of 1.43 m/s2 . At this moment, what is the normal force that acts on...
  29. E

    Normal force on slipping hemisphere

    Homework Statement A hemispherical bowl of mass m and radius R is placed on a rough horizontal surface. Initially the centre C of the bowl is vertically above the point of contact with the ground(see figure). Now the bowl is released from rest. Find the normal force acting on the hemisphere...
  30. Kinetic95

    Static coefficient of friction decreasing with normal force?

    In my experiments, on a flat plane, when I incrementally increase the normal force acting on a rubber block, I am measuring a decrease in the static coefficient of friction. I am also measuring the friction force, which increases as normal force increases BUT this is not a proportional increase...
  31. T

    How to find Torque without Coefficient of Friction?

    Hello! I am an AP Physics student and had a quick question for validity. I was prompted with this question in class today: Example 7: An 8-meter ladder of weight 355 N leans at an angle of 50° to the floor against a smooth vertical wall. Assume the center of weight (gravity) for the ladder is at...
  32. P

    How do I calculate the coefficient of friction in a static friction problem?

    Hi all, I have problem to solve this question: Wb=150N Wa=50N T=150N alph =? µ =? - There is friction between A and B only(Between A and the ramp there isn't). - A and B not moving(first Newton's law). 3. I tried to solve as: But the answer is wrong, can anyone help me please, and...
  33. J

    Normal Force between two concentric cylinders

    Homework Statement a cylinder sits inside of another fixed cylinder without friction and an internal force acts on the cylinder as shown in the diagram. Draw the normal force vector and write down the force and moment equations. I drew in my normal vector to counteract the A force vector and...
  34. Shardul Khare

    B Exploring the Physics of Stacked Blocks: No Normal Force on Block A

    If 3 blocks have some mass(a,b,c) are kept on one another (Vertically i mean)...Why block a doesn't experience the normal force exerted by the ground on block c? won't that force get transferred through b to a?
  35. W

    Equations for Normal Forces at A and B: F_A + F_B = 0d * F_A - b * F_B = 0

    1. Homework Statement This isn't really a problem but an example in an online lecture. I'm trying to understand everything for when I get to harder questions but am having trouble understanding the "d/b" part of the equation. Homework Equations How does dividing d by b help solve for the...
  36. Shardul Khare

    B What's the Difference Between Contact Force and the Normal Force

    Can somebody pls explain this to me?
  37. Hallucinogen

    Is the normal force just kinetic energy?

    I'm confused; forgive me if this dumb. I'm trying to reason what "force" is, on a molecular level. I'm only concerned about normal forces here (pushes and pulls), not field forces. Forces in Newtons are vector quantities and only represent relationships between two things right? It isn't...
  38. G

    When would the normal force not equal the weight?

    Homework Statement I know that on a horizontal surface. if the net force is 0 in the y direction the weight of object=the normal force, but wouldn't the normal force always equal the magnitude of gravity on an object, just in opposite directions? Because if the weight is stronger than the...
  39. Likith D

    B Does Normal force always HAVE to be perpendicular to plane ?

    Say i Have 1. A perfectly spherical and perfectly rigid Ball 2. A perfectly flat and perfectly rigid wall Say i throw the ball at my FLAT wall also giving the ball a linear velocity The only contact with the wall and the ball is a point... a POINT ! So, I can as well forget about the rest of...
  40. B

    How does one find the normal force when not at constant velocity or at rest?

    How does one find the normal force when the object is not at constant movement or at rest.
  41. A

    Centripetal Force, Friction, Loop de Loop, and Normal Forces

    Two questions I had: 1. How is the force of friction of the tires pointed inwards to cause centripetal acceleration? If the tire is rotated when trying to turn, the car is still traveling with a velocity perpendicular to the circle and force of friction would still be counteracting the...
  42. OrlandoLewis

    Why Is the Normal Force the Same on Both Blocks in a Frictional System?

    Homework Statement The two blocks (m=16kg and M=88kg) are not attached to each other. The coefficient of static friction between the blocks is us=0.38, but the surface beneath the larger block is frictionless. What is the minimum magnitude of the horizontal force F required to keep the smaller...
  43. M

    B Understanding the Horizontal Component of Normal Force in Banked Curves

    Why during a banked curve is the horizontal component of the normal force considered as the net force and the centripetal force? The horizontal component of Normal force, N·sinθ, is not even ponting towards the centre of the curvature.
  44. A

    Static friction vs. Normal force on an incline

    I have two surfaces that have a coifficent of friction of .6. Disregarding mass (if possible) at what angle would the force of static friction and the normal force be equal
  45. D

    Calculating Normal Forces on a Wooden Stick Supported by Two Chairs

    Homework Statement An ##D## meter long wooden stick with a mass of ##M## is placed on two chairs of neglegible lenght. The left is ##L## meters from the left end and the right is ##X## meters from the right end. Find the expression for the both Normal forces that act from the chairs. Homework...
  46. Surya97

    Four things -- Normal force, friction, Pressure, breakage

    I understand that every force has an equal and opposite reaction, and the reason things can move is because the forces acts on different things. Also, F=MA is why the heavier object is accelerated less. The equal and opposite reaction to gravity pulling down towards the Earth's core on a book...
  47. G

    Came up with a problem that I can't solve

    Imagine a hoop with mass M and radius R that will only roll without slipping on the floor. Place a point object with mass m on top of the hoop and then the system starts from at rest. Question: where does m leave M? If one fixes the hoop or let the hoop slide, solutions can be found using high...
  48. RoboNerd

    Question about finding static friction coefficient

    Homework Statement Two boxes each weighing 900 N are stacked on a horizontal floor. Box A is on the bottom, box B is on the top. The coefficient of static friction between box a and the floor is 0.3. A worker applies a force of 600 N to box b parallel to the floor, and the stack moves together...
  49. E

    B Elevator action-reaction pair/normal forces

    In the above case, the normal force exerted by the elevator on the box would be = 10kg * g + 10kg*5m/s^2, assuming g = 10m/s^2, the elevator would exert a normal force of 150N on the box. But wouldn't the box exert an equal and opposite force on the elevator resulting in no motion? I know this...
  50. John Pang

    I Why is normal force always perpendicular to the surface?

    Why is normal force always perpendicular to the surface? I understand that normal force is the upward reaction force by a surface due to an external action force pushing the surface. Then, if I apply an extermal force on a non inclined surface at an angle, let's say 30 degrees, shouldn't the...
Back
Top