What is Normal force: Definition and 470 Discussions

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.

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  1. I

    How Do You Solve for Normal Force in Different Dynamics?

    Homework Statement The problem motivating this post is: "An out-of-gas car is rolling over the top of a hill at speed v. At this instant, a. n > FG b. n < FG c. n = FG d. We can't tell about n without knowing v." (Associated figure attached.) Homework Equations [/B] Newton's second law The...
  2. A

    Normal force of real pulley: Which direction is it?

    Consider a pulley fixed to the ceiling. A mass-less string is wrapped around it, with each side of the string hanging down either side of the pulley. Since the pulley has friction with the string, tension along the string will vary. Let's say the string is attempting to move clockwise, so the...
  3. gcombina

    Normal Force and Coefficient of Kinetic Friction

    A 250-N force is directed horizontally as shown to push a 29-kg box up an inclined plane at a constant speed. Determine the magnitude of the normal force, FN, and the coefficient of kinetic friction, µk. So, I know I have to find the vertical and parallel forces Vertical: Fn and 250 sin of...
  4. gcombina

    Normal Force and Coefficient of kinetic friction (Quiz 4, q15)

    A 250-N force is directed horizontally as shown to push a 29-kg box up an inclined plane at a constant speed. Determine the magnitude of the normal force, FN, and the coefficient of kinetic friction, µk. FN µk (a) 330 N 0.31 (b) 310 N 0.33 (c) 250 N 0.27 (d) 290 N...
  5. S

    Normal Force in Circular Motion

    Hi all, For a marble in uniform circular motion within a smooth cone, what is the relationship between the normal force by the surface of the cone and the weight of the marble? My take is that the normal force forms a reaction pair with one of the resolved forces of weight. I have resolved the...
  6. T

    Engineering Statics Question Regarding Finding Normal Force

    Homework Statement http://i.imgur.com/rwbXqW8.png Homework Equations The Attempt at a Solution So I started off by analyzing the pulley, and determined that each cable carries 100N of force. After that, I drew the FBD of the beam, where there is a 100N force going downwards on the...
  7. M

    Going back to basics: The Normal Force

    So, usually I like to give a long description of how/why I am asking such a question, but I think this time, I'll be quick and to the point. Truth is when I first came to this site, I think I started asking questions that were well beyond my current knowledge, so I would like to take the time...
  8. Z

    Loop-the-loop normal force problem. Possible textbook error?

    Homework Statement A pilot of mass m flies a jet plane on a "loop-the-loop" course by flying in a vertical circle of radius R at a constant speed v. The force that the cockpit seat exerts on the pilot at the top of the loop is (A) mg. (B) mg\left(\frac{v^{2}}{R+1}\right). (C)...
  9. Curieuse

    Normal force on block placed on incline.2 approaches different result

    Homework Statement The problem wants me to order the choice for the directions of a force F of a constant magnitude F(a,b,c,d are unit vectors along which F has to be oriented) exerted on the block placed on an incline at 30° to the horizontal based on the normal force Fn that the incline...
  10. F

    How Does Speed Affect Normal Force at the Crest of a Hill?

    Homework Statement A 1300 kg car is traveling at 25 m/s as it passes the crest of a hill that has a radius of curvature of 120m. Determine the normal force acting on the car at the crest of the hill.Homework Equations The Attempt at a Solution I know that for horizontal surfaces the Normal...
  11. S

    Finding the Normal Force on the Rod of a Paper Roll

    Homework Statement A large 16.0 kg roll of paper with radius R=18.0 cm rests against the wall and is held in place by a bracket attached to a rod through the center of the roll. The rod turns without friction in the bracket, and the moment of inertia of the paper and rod about the axis is...
  12. S

    Normal Force in Space: Ball on Table in Spacship

    imagine there is a ball on a table on a spaceship that is not moving there is no gravitational force acting on the ball will there be a normal force
  13. E

    Does the normal force do work?

    Homework Statement Consider the mass m1 on a simple incline plane. It passes from point A downwards with the velocity v0 and stops at point B (still on the plane). What is the work done by the normal force on mass m during the complete motion? Homework Equations The Attempt at a...
  14. N

    Why is the Normal Force Neglected in Certain Scenarios?

    So why does normal force of the wheel not counted or drawn in the diagram?? Isn't it that whenever there's mg, there's also Fnormal? Thanks!
  15. A

    Questions about entropy, normal force, and the human body

    Greetings folks, I'm new to this forum and to physics in general so apologies if I come off like a greenhorn or if I am posting these questions in the wrong place. I have an Arts background and have never really "gotten" science, but my interest in post-Enlightenment philosophy has led me to a...
  16. J

    Gravitational force and normal force.

    Homework Statement 1) A 0.25kg book rest on a table. A downward force of 9.5 N is exerted on the top of the book by a hand pushing down on the book. 2)what is the size of the normal force exerted by the table on the book Homework Equations F=ma The Attempt at a Solution 1)...
  17. L

    Understanding Normal Force in a Vertical Spring System

    Homework Statement A vertical spring is fixed on a table. A book is put on the spring. The book compresses the spring until static equilibrium is reached. Question: Is there a normal force exerted by the spring on the book? Why or why not? Homework Equations The Attempt at a...
  18. R

    Normal Force: A summation of electromagnetic forces?

    Obviously it makes sense when considering the force of weight and the fact that the object is not moving up or down, but what is it composed of? What I mean is, the ground you are standing on is made of molecules bonded through the electromagnetic force, right? But those bonds are parallel to...
  19. R

    Normal Force Problem: Find Contact Force b/w Sphere, Wedge A & Wall B

    Homework Statement Find Normal Contact force between the sphere and wedge A and wall B. All surfaces are frictionless and in rest. Diagram :- 2. The attempt at a solution Let normal force on A be N and on B be R. My Diagram :- By The Diagram, N = mgcosθ ...eq(1) R = Nsinθ ...eq(2) =...
  20. U

    How Do Friction and Normal Force Affect Stability in a Pinned Structure?

    Homework Statement Three points, ABC and a downward force exerted at O. C is pinned to a vertical wall. C to B extends horizontally for 15m. At B, a bend occurs downwards to point A on the ground. The downward force is applied between points B and A at point O. The horizontal distance...
  21. Boxlife27

    Conceptual Normal Force Question

    ~~Conceptual Normal Force Question~~ Hello! Suppose there is a meter stick suspended from and parallel to a table. On one end, the meter stick is held up by a piece of string at an angle. On the other end, the meter stick is held up by a metal thing about 10cm tall, simply allowing the stick...
  22. G

    When normal force isn't normal l

    When normal force isn't "normal"l Homework Statement A box with a certain mass is pulled across a horizontal surface by a rope at an angle. Figure out the components, the friction, the acceleration of the box, when the tension in the rope, its angle, the mass of the box, and mu are given...
  23. N

    Cannot understand Normal Force, Solution to problem

    Homework Statement I am studying the solution used for the following question: http://answers.yahoo.com/question/index?qid=20131014213456AA4eCNl And I am unable to understand why normal force Fn = mgcosΘ + PsinΘ Should it not be just Fn = mgcosΘ, When drawing the FBD, the only...
  24. N

    How Is the Contact Force Between the 7kg and 11kg Blocks Calculated?

    Homework Statement You are pushing four blocks of masses 4, 7, 11, and 17kg positioned next to each other on a frictionless surface. Find the force of contact between the 7 and 11kg blocks when you push the blocks with a 190N force to the left. They are arranged as such: |17||11||7||4|...
  25. T

    What is the normal force between two stacked boxes?

    A 10.0-kg box is placed on top of the 19.0-kg box, as shown in the figure. Determine the normal force that the 19.0-kg box exerts on the 10.0-kg box. i know what the normal force of the 19 kg box. i am having problem setting these kind of problems.
  26. U

    Calculating Impulse of Normal Force in a Frictional System with Thrown Ball

    Homework Statement Stick of mass M resting on frictional surface with friction coefficients μk=μs. From the center of the stick at time t=0 a ball of mass m thrown to the right with an angle θ above the horizontal and with speed v0. As a result of the throwing there is an impulse on the y...
  27. M

    Frictional force and Normal force

    when a body is slided or move in a horizontal floor, the Frictional force is directly proportional to the Normal force acting on the body. Is there is any proof (emperically or Theoretically)
  28. X

    Banked turns; do we use the x component of normal force or gravity?

    I am confused on what the correct way to do this is. In my old physics textbooks, they say that the x component of gravity is responsible for the centripetal force. However, on the internet and for more advanced topics they say it is the x component of normal force that is responsible for...
  29. S

    Normal Force and Atmospheric Pressure

    1. Suppose a cube of mass m is lying at rest on a horizontal surface. The area of one face of the cube is A. For the equlibrium of cube no net force acts on it. If we consider the vertical direction then the contact force N should be equal to the force due to gravity plus the force due to...
  30. J

    Normal force on a car rounding a banked curve

    This is my first thread on the forum. I'm really glad to have found this wonderful resource. I have a lot of intuition in mathematics and one of my dreams has been to have the same level of intuition in physics. With your help I hope I can achieve that. I was reading an example in Physics...
  31. S

    Extreme Confusion of centripetal acceleration force and normal force

    Hi guys, first off, thanks for answering my previous question... Now here's another one. I got confused by my school's homework a bit...so there's a car that travels over a humpback bridge with a radius of 45m, so basically it's a semicircle bridge, and so I'm supposed to calculate the...
  32. A

    Normal force for a lever model

    My model is a lever on a table top. One arm is horizontal on the table, while the other arm is raised at an angle alpha. I'm assuming the weight of the horizontal lever (F) acts at its center of gravity at a distance f from the pivot, while the weight of the raised lever (W) acts at its center...
  33. W

    Understanding Normal Force: Exploring Contact and Surfaces in Block Systems

    If there are 2 blocks beside each other and a force is applied to the first block, the first block will push the second block has well. This means that the two blocks are in contact. So why isn't there a normal force drawn perpendicular to the side of the second block if it is in contact with...
  34. H

    Why is normal force in the direction of vector normal?

    This might be a bit philosophical, but is this just from experiment? that for a really really smooth surface, people found that the net force on an incline surface is found to be approximately in the direction normal to the incline plane? (approximately because there's no perfectly smooth...
  35. C

    [Hanging/Sliding Chain Problem] Confusion in Normal Force

    This is a very basic problem which you all must have seen somewhere. But recently an itching doubt has come up to me regarding this problem. Problem: A chain lies on a table with some part of it hanging over the edge. Now if the coefficient of friction is μ, then find out the maximum part...
  36. M

    Normal Force of a hoop rolling down an inclined plane.

    Homework Statement I have a question from my homework. My homework is completed, but I've been running some thought experiments lately and I wish to conceptually discuss this. The problem has to do with a hoop rolling down an inclined plane. I had to find the Normal Force using...
  37. G

    What exactly is the Normal Force?

    I know that every action has a reaction, and I understand that applying a force on a surface yields a "force" from that surface to hold it up, and that it's magnitude and direction are equal and opposite, respectively. But conceptually, what is happening? Defining a force in terms of another...
  38. J

    Why does the normal force affect friction?

    Homework Statement I am student teaching a class about static friction soon. I am worried a student is going to ask me where Fstatic friction = μ sFnormal comes from. I am not sure how to explain it. Homework Equations The Attempt at a Solution I've always thought of it this...
  39. S

    Why are there two different equations for normal force on an angle?

    Homework Statement I feel like I am being told that there two different kinds of normal force. 1st. In grade 11 we were always told that normal force on an angle equals m*g*cosθ, where Fn equals the y-component, and θ is the angle between Fn and mg. 2nd. Now in university we are told...
  40. G

    How do I find the normal force?

    Homework Statement Let's say I'm holding a crate up against the ceiling with a force of 'P', and the crate is stationary. What is the normal force? Homework Equations Newton's 1st law: ƩF=0 The Attempt at a Solution I have three forces acting on the crate - The normal force...
  41. N

    Find the Magnitude of the Normal Force on the Slider and v'

    Homework Statement A 2.4-lb slider is propelled upward at A along the fixed curved bar which lies in a vertical plane. If the slider is observed to have a speed of 11.3 ft/sec as it passes position B, determine (a) the magnitude N of the force exerted by the fixed rod on the slider and (b) the...
  42. C

    FBDs for Box and Magnet Lifting by a Rope Attached to Ceiling

    Homework Statement A box is lifted by a magnet suspended from the ceiling by a rope attached to the magnet as illustrated in Fig 3.65. Draw free body diagram for the box and for the magnet so the picture is basically there is a ceiling , and the rope hanging from the ceiling to the...
  43. F

    How to Calculate Normal Force on an Inclined Surface with Tension Force?

    Homework Statement I've been having a little bit of trouble answering this question: "An 8.0 kg wooden sled is pulled over the snow by means of a rope that makes an angle of 40° with the horizontal. If the rope has a tension of 70.0 N, what is the normal force acting on the sled?"...
  44. K

    Find period of astronaut when Normal force of ship = normal force on earth

    Homework Statement If the gravitational acceleration at Earth's surface is given by: g = GMe/Re^2, show that the period of rotation of a spaceship needed to make an astronaut feel the same normal force on the ship that they would feel on Earth, when it is given by T = √[(4pi^2)(Rs)(Re^2)/GMe]...
  45. PhanthomJay

    Space between objects when Normal force equals 0

    Ok, so 2 objects in contact with one another exert a normal force pair between the 2, but it is my understanding that they never 'touch' each other, rather, it is the repulsion of the outer electrons that create the electromagnetic 'normal' force. QUESTION 1: Is there physical space betwen the...
  46. B

    When does the normal force act on something?

    A bit confused about the operation of normal forces. When does a normal force act due to some surface on an object? When the object touches the surface or when the object actually applies a force on the surface? The reason I ask this is because I am confused about normal forces...
  47. F

    Normal force max min constraints on a roller coaster

    Homework Statement passengers cannot have a normal force equal to 0 or greater than 4 times their weight. What are the heights H1 and H2. Coaster starts at H1 and and ends at H2. H1>H2 and there is a low point between the two hills defined as zero height. The radius of the curve at the...
  48. A

    Normal Force While Going Up Stairs

    In my high school physics class, we are doing an experiment where we go up a flight of steps, record the time it takes, and calculate the work done in the vertical direction. I understand everything (I am a pretty bright student) except one part that I simply cannot wrap my head around. To...
  49. C

    Normal force in rotational motion

    Hi there, I've got a conceptual question about the normal force as applied to rotational motion. Suppose you have an object like a uniform disk. If the disk were set up so that its axis of rotation were about its centre of mass, it would just sit there and the normal force would be equal to...
  50. A

    Normal force in circular motion

    Hi, Suppose we have a fellow on a ferris wheel. Would the normal force be greater on the top or at the bottom of the ferris wheel? I'm thinking that it would be greater at the top, or am I wrong? Thanks,
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