# What is Normal force: Definition and 462 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. ### Work done by a normal force (or rather, work NOT done)

This question states that the normal force of the stairs on the woman does NO work. I do not understand how this can be. I would reason like this: The woman propels herself up the stairs using her legs. Her legs push down against the stairs, and the consequent normal force pushes upwards on her...
2. ### Tipping Point of Stationary Barbell

TL;DR Summary: Please Help. I need an answer for an Investigation if a uniform bar of length 2200mm is supported evenly on 2 points (1 and 2) 1190mm apart. The bar is comprised of 3 sections (A, B and C) of varying masses. Section A and C have equal mass and volume and is comprised of the...
3. ### what are the forces on a cell in a tree vs on the surface of a tree

Hey everyone. Let's say you have a tall tree. say, 10 m tall. Take a cubic cell 1mm in dimensions. Suppose the cell is at 1 m high in the center of the trunk of the tree. What are the forces acting on the cell? let's say tree cell's mass is t grams. its weight is F= ma = t (9.8) = 9.8 t...
4. ### Acceleration & Normal Force of a Box: 4 m/s2 & 418 N

What is the acceleration of the box? Paper says the answer is 4 m/s2. What is the Normal force acting on the box? Paper says the answer is 418 N. I know that for most cases FN=Fg=W. So, by definition the "original" Normal force is 245.25 N (am I correct?) I calculated the Fay which is...
5. ### The FBD Mystery: Why Isn't Normal Force Along Radial Line?

so this is what the FBD is.... but to be fair, to me this one looks as if the normal force in the direction of the radial line, yet it isn't???? here in the solution, it's not along the radial line, whys that???
6. ### Angle between normal force and radial line for cylindrical coordinates

so I was wondering. there is this normal force on the can from the path. And there's this formula to find the angle between the radial line and the tangent or also between the normal force and either the radial or theta axis. the formula is ##\psi = r/dr/d\theta##. The thing is that here they...
7. ### Loader Boom maximum bending moment

TL;DR Summary: Finding maximum bending moment on a boom I am trying to solve the problem stated in the picture below. The answers are given. I've manage to find the Normal and Shear Forces but I'm stuck at the bending moment. According to my analysis the maximum bending moment is +7208,1...
8. ### A Normal force and force of friction inside a tube

Dear all, Me and some colleagues (non-physicists) are discussing how force works when passing a cylinder (which we are holding) into a narrow tube. As we insert more of the cylinder into the tube, the force we are exerting is increasing. My theory is that the normal force is increasing and his...
9. ### The maximal normal force (Friction with slanted surface)

The problem that I immediately ran into was how I would calculate N without knowing Fmax. I didn't think the y-component of N would simply be the same magnitude as mg. After being stuck for a good while I even tested if it was, by dividing the magnitude of mg with cosθ, which of course ended up...
10. ### Normal force at the top of a vertical loop -- Circular Motion Dynamics

From the equation for centripetal force, I can see that the centripetal force is proportional to v^2. Does this have something to do with why there is a normal force at the top? Does the velocity of the object require there to be a normal force? If so, why is that the case?
11. ### I Reaction force of and its relation to normal force and friction

Hello, When we consider a block sitting on a surface, the gravitational force ##W## and the normal force ##F_N## are applied to the block. Both equal i magnitude and opposite in direction. We call the normal force the reaction force exerted by the surface on the block. Now we consider the...
12. ### B Normal Force Discrepancy for Wedge Vs. Ramp

I have seen a few posts on this subject before, but none have really answered my question. For clarity, I will refer to the 1st example as a wedge, and the second as a ramp (although both are of course inclined planes). With both examples that I outline below, we will assume no friction, and a...
13. ### Distribution of normal force in this problem

It is crystal clear that we need torque equation to solve this. But, in order to do so, I need to know where the normal force is located. As far as I'm concerned, normal force is not distributed equally. If this is true, then I suppose this problem is unsolvable? (Though the book says thay it is...
14. ### Coefficient of friction and normal force

The answer should be no change but we know ##F=ma##. In this eqn when acceleration increases mass decreases for same force. So why not here? If normal is doubled ##\mu## should be halved.
15. ### Two masses connected by a rope on a pulley on a ramp

I have no clue how to do the problem. I created a free body diagram for each block. I assume that it is simpler than I am making it out to be.
16. ### I Normal force and details of the Earth holding up an object

It's a simple application of Newton's third law to show that the Earth indeed does accelerate towards an object as it falls towards earth. M_o is the mass of the object M_e is the mass of the earth From the third law (and ignoring air drag): M_e * a_e - M_o*g = 0 (with a up-positive...
17. ### Forces acting on a car on an incline

For part 1, I got ## tan \alpha = 1/30 ## ##\alpha = 1.9^{\circ}## ##mgcos(1.9) = 10774N## I'm a little thrown off by the second part. Are we supposed to assume that in the absence of friction, F = N and then substitute F = ma to solve for this?
18. ### Gravitational potential energy question - normal force on us

Hi, If we are standing on the ground, the Earth applies a force equal to our weight to us, but why do we feel a greater force when we fall to the ground from a certain height? Our weight is the same along this small height because our mass and acceleration are the same and, even so, the normal...
19. ### Finding the normal force of a block under water, under pressure

So since the block is at the bottom there's no pressure pushing it up. To calculate the mass and force of gravity, I multiplied the density of the block by its height and cross sectional area and got 564 kg. Multiplying this by 9.8 I got the force of gravity of 5527.2 N. Now to find the force...
20. ### Forces on a crate with friction: find the normal force

I have attempted this problem by solving for the normal force. (16.73)(9.8)-51.25(sin)(49.1). I tried to work that out but it was incorrect because apparently the vertical force is zero. Could I get an explanation on what that means and where I should start?
21. ### Normal force on a rod by the rim of a bowl

I want to ask the direction of normal force acting on the rod by the rim of the bowl. Is the direction perpendicular to the rod or will it be directed horizontally to the left? My guess would be horizontally to the left because the normal force would be perpendicular to the "plane / surface"...
22. ### [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...
23. ### 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...
24. ### Direction of the normal force when acting on a tilted object

My question is: given a rigid body which interacts with a surface, what's the direction of the normal force? Because, as the word says, it has to be normal to the surface. But when treating problems of a vertical rod which is slightly pushed and forms an angle ##\theta## with the surface, some...
25. ### Normal force acting on a block on an accelerating wedge

We have a wedge whose surface is ##\theta## from the horizontal surface. After a block is placed on its frictionless slant surface, the wedge starts to accelerate due to a force F. What is the normal force acting upon the block? I have been trying to solve it but I got no clue. Could someone...
26. ### Is Gravity the only force doing work on a roller coaster cart?

Why I think gravity *is* the only force doing work on the rider: 1) The only forces acting on the rider are gravity and the normal force. Broken down into their component vectors, we have: -> The component of the force of gravity moving parallel to the rider's direction of motion -> The normal...
27. ### Calculating the normal force with Newton's Laws

Block A is accelerating at a= 49.6/0.5 m/s (99.2m/s) Block B force is F= 3kg * 99.2 = 297.6N but I'm not sure where to go from here?
28. ### Can the Normal Force Produce a Torque on an Object on an Incline?

Hi everyone I can't understand how normal force produce torque isn't normal force acts normally on the plane so the perpendicular distance in case if it was like block will be zero, so normal force doesn't produce torque. "case of box"
29. ### Normal force between stacked boxes

Σ F= -F(gravity from earth) + F(normal from earth) -F(normal from top box) +F(normal from bottom box) = (2+5) * 2.5 The forces from gravity and it's normal force cancel out, leaving us with the normal forces from the boxes. F(net of normal from boxes) = (2+5) * 2.5 = 17.5N
30. ### Calculating the normal force due to moment load on a thrust bearing

Hello all! I have a mathematical question for you. I'm trying to design a thrust bearing that can withstand axial and moment loads. I've added a picture of a similar design. The design consists of two rings (grey) and sliding pads (blue) fixed on the bottom ring. The top ring slides over the...
31. ### B Quick Question About Normal Force

Guys I was just wondering if normal force is a contact force. Obviously it is considered a contact force but it also has something to do with the repelling of atoms. In my mind, normal force is a fundamental truth, but technically, are two objects touching or is there a minuscule space between...
32. ### Normal force against a wall

I want you to tell me if I'm right For 1), does ##m_2## feel a normal force? Because I don't think so, since it isn't pushing the wall. For 2), ##m_2## suffers a normal force because it feels a pseudo-force to the left and so it pushes the wall
33. ### What is the normal force in A and B?

A welded square frame consisting of four equal rods each with mass m and length 2l can move in the vertical plane by means of two small wheels in A and B that move without friction along a horizontal and vertical track, respectively. The disc is released from rest in a position where the sides...
34. ### B Normal force of a body over a circular bridge

I am not able to understand why normal force on top in a vertical circular motion the least. Also please help me with normal force of a body over convex and concave bridges. Why do we get these equations: N=mg-mv2/r (convex bridge) N=mg+mv2/r (concave bridge)
35. ### Normal Force and an elevator

Consider a body inside an elevator. When it goes up and down, I believe that normal work (positive on the rise and negative on the descent). My question is: since the total work on the closed path is zero, can we say that the normal force is conservative?
36. ### Identifying forces (normal force, weight, gravity)

When an object is resting on a surface such as the floor, there are exerted on it two forces: The normal force - force of the ground - and the weight (the force of gravity, the Earth pushing the object down), the forces drawn on the left. What are the forces on the right? Are they the same as...
37. ### Free body diagram problem

Hello everyone. I find the following problem confusing. A board sandwiched between two boards in the figure below weighs 95.5N. If friction exists between the middle and the compressing boards, draw the free body diagram of the middle board. Below I attached the diagram found in the solution...
38. ### Find normal force, shear force, bending moment

Hello. This is a basic statics/mechanics of materials problem. Here's an image of my work. I've taken a course in statics before, and this is supposed to be review, but I can't seem to get the correct answers which are V_c = 75 lb, M_c = 1125 lb*ft. I've chosen the right side, and it seems as...
39. ### Direction of Normal Force

Homework Statement Part a of the image below. When I try to solve this question, I can't get the solution in the answer key. In the answer key the y component of the normal force is NCos(alpha) in the last line. Does the normal force not point perpendicular to the ramp? Homework Equations...
40. ### How to find the normal force of a car jack lifting a car

Homework Statement A car is lifted vertically by a jack placed at the car's rear end 40cm off the central axis, so that the weight of the car is supported by the jack and the two front wheels. The distance between the front wheels is 1.60m, the distance from the axis connecting the two wheels...
41. ### Normal force on a suitcase

Homework Statement Dylan is rushing to catch a flight. As he walks in the airport he pulls his suitcase behind him, which is rolling on its wheels. The mass of the suitcase is 20.0kg. Dylan pulls on the handle so that he exerts a force on the handle of 100N, 30° above the horizontal. Determine...
42. ### 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...
43. ### 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...
44. ### 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...
45. ### 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...
46. ### 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...
47. ### System of equilibrium, why won't the normal force apply?

Homework Statement Homework Equations The 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...
48. ### 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
49. ### 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...
50. ### 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...