# Do Normal Forces Always Exist When Surfaces are in Contact?

• ritwik06
In summary, the question is whether a normal reaction is necessary when two surfaces are in contact. The initial answer is "no", supported by an example of a block in a freely falling lift. However, the book being used states "yes", without providing an explanation. It is suggested that this may be a misprint.
ritwik06

## Homework Statement

Is it necessary to have a normal reaction whenever 2 surfaces are in contact with each other?

## The Attempt at a Solution

I thought the answer was "no". But my book says "yes".
I can support my answer with an example:
the normal force between the surface of a block and the floor of a freely falling lift under gravity is zero.

Please help me. Does my book author takes the molecular level forces into account when he goes on to say "yes"?

What book are you using? Does the book give an explanation or just make a statement?

I would say that in the usual sense of the term you can have a zero normal force between surfaces in contact.

Doc Al said:
What book are you using? Does the book give an explanation or just make a statement?

I would say that in the usual sense of the term you can have a zero normal force between surfaces in contact.

Its called "The Pinnacle FIITJEE package for Newton's Laws". I was just going through it when I found this.
It has just made an emphatic "YES" with no explanations whatsoever.

Thanks a lot. I think it might just be a misprint or something.

## 1. Do normal forces always exist when surfaces are in contact?

Yes, normal forces always exist when surfaces are in contact. Normal forces are perpendicular to the surface of contact and are present whenever two surfaces are touching each other.

## 2. What is the definition of a normal force?

A normal force is a contact force that acts perpendicular to the surface of contact between two objects. It is a reaction force that prevents objects from passing through each other.

## 3. Are normal forces always equal in magnitude and opposite in direction?

No, normal forces can vary in magnitude and direction depending on the weight and orientation of the objects in contact. However, they are always perpendicular to the surface of contact.

## 4. Can normal forces exist between non-solid objects?

Yes, normal forces can exist between non-solid objects such as liquids and gases. In these cases, the normal force is caused by the pressure exerted by the fluid on the object.

## 5. Can normal forces be greater than the weight of an object?

Yes, normal forces can be greater than the weight of an object when additional forces such as friction or external forces are present. This is known as an "overcoming" normal force and is necessary for an object to be in equilibrium.

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