How To Find Normal Force On A Horizontal Surface: Several Approaches and Problem Examples


In this article, we will be talking about the normal force on horizontal force. To know how to find the normal force on a horizontal surface, continue reading this article. 

The normal force kept on a horizontal surface acts in the perpendicular direction to the object. This force keeps the object intact on the surface and avoids its falling. Let us know several approaches on how to find normal force on a horizontal surface. 

In physics, the normal force is the component that acts on an object by the surface with which it is in contact. It is called “Normal” force because it acts normally i.e at right angles on the object.  For instance, if a person stands on a hill and he does not fall, it is because of two forces: The friction force and the normal force. 

We have seen how to find normal force for different cases. Now, most ask whether normal force is horizontal or vertical. So, before answering this question, let us know what the normal force on a horizontal surface is.

What is the normal force on a horizontal surface

Any object kept on a horizontal surface like a flat table, stand, or simply ground is an example of the normal force on a horizontal surface. For instance, books kept on the bookshelf or laptops on the office desk. 

how to find normal force on a horizontal surface

So, in all these cases, the normal force, like always, will act in the upward direction perpendicular to the object. Look at the figure above to know the direction of the normal force. According to the above free body diagram, we will have:

N = W

N = mg

Here,

N is the normal force 

m is the mass of the object and 

g is the acceleration due to gravity. 

We can also find the normal force on the horizontal surface using the coefficient of friction. The basic formula of friction is f =mu N; from this, we get N = f/mu. mu is the coefficient of friction which tells the measure of friction acting between the surface. 

So using the formulas mentioned, we know how to find the normal force on a horizontal surface. For the inclined surface or force acting at an angle, we use a different formula and other approaches to find normal force. 

Can normal force be horizontal

We have seen above how to find the normal force on a horizontal surface. In all the cases above, it is obvious that the normal force is vertical; that is, it acts upward. But can a normal force be horizontal? Let us answer this question. 

For any object kept on a horizontal surface, the normal horizontal force would mean that it would act parallel to the surface. But this case is not possible as we know that the normal force in all the cases is perpendicular to the object and acts in the upward direction. 

For the horizontal body, the normal force exists in the same way as explained in the above section. 

Is normal force horizontal or vertical

The normal force keeps the object in its place and restricts it from passing through the surface. All the objects, including us humans, experience the normal force. It is just that the measure of this force is so low that we don’t feel it. 

Image Credit: Pixabay

The normal force is a vertical force which means it always acts in the upward direction. This force is perpendicular to the object. For example, look at the figure above; the cup kept on a table experiences a normal force in the vertical direction that balances its weight and keeps it from falling off. 

Even if the object is placed on some surface inclined at an angle, then also the normal force would be vertical. To understand it better, look at the figure above. The surface is inclined at an angle theta, and a box is kept on it. The normal force acting on it is vertical and perpendicular to the box. 

So, now we know that the normal force is vertical and how to find the normal force on a horizontal surface. Now let us look at some of the problem examples. 

Problems On How To Find Normal Force On A Horizontal Surface

Problem 1) A box of mass 2 kg is kept on a table. What would be the normal force acting on the box? 

Solution: In this question, we are given that the mass of the object is 4 kg, and the acceleration due to gravity is 9.8 m s-2. Therefore the normal force fN would be:

fN = m g

fN = 4* 9.8

fN = 39.2 N 

Problem 2) The force of friction acting on an object is 9.5 N. The coefficient of friction being 0.6, find the normal force. 

Solution: We are given:

f = 9.5 

mu = 0.6

Therefore the normal force would be:

N = f/mu

N = 9.5/0.6

N = 15.8 N

Frequently Asked Questions (FAQs)

What is the normal force on an object?

The force acting on any object normally (perpendicularly) is called the normal force. 

When a body is in contact with a surface, a perpendicular force acts on it that in a way balances the weight and prevents it from passing through the surface. 

Explain normal force on a horizontal surface. 

For an object kept on a horizontal surface, the normal force acts in an upward direction. 

For the object kept on a horizontal surface the normal force would act in an upward direction and weight downward. Both forces balances out each other and thus normal force equals to weight of the object for general horizontal surface. 

How to find the normal force on a horizontal surface? 

We can find the normal force on a horizontal surface using a few formulas. 

For an object kept on a surface, we get N = mg, which is used to find normal force. Secondly, using the friction formula f = mu N , we can calculate the normal force on a horizontal surface

Is normal force always equal to the weight of the object? 

No, the normal force is not necessarily exactly equals to the weight of the object. 

It can be greater or smaller than the weight in certain cases like:

N = m g + F sin θ, when a force acts in a downward direction.  N = m g – F sin θ when a force acts in an upward direction.

Rabiya Khalid

Hi,  I am Rabiya Khalid, currently pursuing my masters in Mathematics. Article writing is my passion and I have been professionally writing for more than a year now. Being a science student, I have a knack for reading and writing about science and everything related to it. If you like what I write you can connect with me on LinkedIn: https://www.linkedin.com/mwlite/in/rabiya-khalid-bba02921a In my free time, I let out my creative side on a canvas. You can check my paintings at: https://www.instagram.com/chronicles_studio/

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