# 7 Neutral Equilibrium Example: Detailed Explanations

This article will is based on neutral equilibrium example. When we hear the word equilibrium, we instantly think of balance between objects or forces. This fact is true that equilibrium directly relates to balance between two or more objects.

In this article, we will study further about equilibrium. It is more than just balancing. First we will discuss about different types of equilibrium. We will keep our focus on neutral equilibrium in this article.

## What is equilibrium?

As discussed above, equilibrium is a state of system in which all the forces are balanced or cancel each other. Equilibrium is very important in every field, be it chemistry or physics or engineering or in everyday lives. Equilibrium means balance, without balance it will be very difficult for lives to be simple.

Equilibrium can be broadly classified as- Mechanical equilibrium, chemical equilibrium and thermal equilibrium. Mechanical equilibrium is also divided further into sub categories out of which one such type is Neutral equilibrium (other sub types are stable equilibrium and unstable equilibrium). Lets see what is neutral equilibrium.

Image credits: KkuThermal equilibrium in closed systemCC BY-SA 4.0

## Equation of equilibrium of forces

When multiple forces act, then it gets difficult for an object in a stable path or remain stationary. If the forces act in such a way that these forces cancel each other out then it gets easier to keep the object stable.

Lets consider two forces F1 and F2 acting on a body A. The two forces act horizontally in first case and vertically in other case. For the body to be in equilibrium in both the cases, following conditions should be satisfied-

• 1st case- For the body to be in equilibrium all the forces should cancel each other that means sum of all horizontal forces should be zero.
$\sum F_{x}=0$

where,

Fx represents all the forces in X direction

• 2nd case- For the body to be in equilibrium all the forces should cancel each other that means sum of all vertical forces should be equal to zero.
$\sum F_{y}=0$

where,

Fy represents all the forces in Y direction

## What is neutral equilibrium?

Neutral equilibrium is the type of equilibrium in which the body comes to rest in its new position after being slightly displaced by some external force.

The body does not move after attaining neutral equilibrium that means it remains stationary. This is the compulsory condition for neutral equilibrium. If the body moves to its original position then it should have been moved by an external force.

The body does not come back to its original position rather remains stationary at the new position.

## Neutral Equilibrium Example

Now we have an idea about neutral equilibrium, lets get a more clear about it by looking at some examples given below.

We experience neutral equilibrium in our daily lives, lets see the examples of neutral equilibrium we see in everyday lives-

## A marble lying on a horizontal surface, undisturbed

The marble is not moving as there is no force acting on it. The marble is lying there on its own without any support of external force. It will only move when an external force is applied on it. Hence it is said to be in neutral equilibrium.

## Sliding a book on the table surface, the book comes in neutral equilibrium after coming to rest

As the action of force diminishes, the book attains neutral equilibrium.

## A football lying on the ground

When the ball is lying on the ground untouched, it does not move. An external force is required to move the ball. Without any external force, it will keep lying there. Hence it is neutral equilibrium.

## A car parked without handbrakes (no external force applied for it to remain stationary)

When handbrakes are not applied it means the car is stationary on its own and no external force is applied to hold it stationary hence it is in neutral equilibrium.

## A roller lying stationary on a flat surface

A roller will roll as soon as it is touched by an external force, when it is lying undisturbed the roller is said to be in neutral equilibrium.

## Applying viscous cream on hands (for example sunscreen)

Viscous creams/fluids won’t move until an external force is applied on them. Like in the case of sunscreen we need to apply shear force to apply it without which it would not spread by itself.

## A flask lying on ground

A flask lying on ground is stationary, it will not move unless a force is applied. Hence it is said to be in neutral equilibrium.

## Pushing a heavy box

Once we start pushing a heavy box, the object starts moving but the moment we stop pushing the object stops moving. It does not move any further on its own nor it comes back to where it started moving. Hence it is in neutral equilibrium,

## Throwing a heavy object on floor, it comes to rest as soon as it lands on floor

When we throw a heavy object on floor, the object goes down due to the force of gravity. When it lands on the ground, due its own weight it fails to bounce against the gravity. Hence, it stays there without getting lifted from the ground. Hence we can say that the object is in neutral equilibrium.

## Neutral equilibrium of floating bodies

When a body is floating, it is said to be in neutral equilibrium when the body neither returns to its original position nor it moves any further.

M is the meta centre of the body. If it lies exactly at the same point where gravity, G lies then the body is said to be in neutral equilibrium.

## What do you mean by stable equilibrium?

We have seen that in neutral equilibrium the body remains in its new position. Now in stable equilibrium the body comes back to its original position after the force is lifted up or is no more acting on it.

The displacement occurs as a result of external force applied on the body. Neutral equilibrium and stable equilibrium may sound similar but are different from each other.

## Is stable equilibrium and neutral equilibrium same?

Stable equilibrium and neutral equilibrium might sound similar but they are different from each other. Although there is not much difference between them either.

The primary difference being that in stable equilibrium, the body comes back to its original position but in neutral equilibrium the body remains stationary at the new position without moving back to its original position or moving any further.

## What is unstable equilibrium?

Unstable equilibrium is a state of the body where even a small movement in the body will result in a big change. That means the body is so unstable that a slight push will hamper its equilibrium condition.

We can observe unstable equilibrium in everyday lives. For example, if we place a pointed tip on a book and move the book slightly, the pointed top immediately falls down. Likewise if we place a bottle having a narrow cap upside down, it may stay stationary but as soon as a slight force is applied, it will fall down.

## Significance of equilibrium

We all have experienced that perfection comes with stability. In Physics, we can observe that every atom experiences certain kind of force.

• The atom is stable because the inter atomic forces are balanced The moment we try to split an atom, we get an atomic bomb!
• While using a pair of scissors we find it inconvenient if the object is moving here and there, we can cut easily if it is clamped or held by hand.
•  Walking on an inclined road is difficult because we are working against the gravity hence equilibrium is disturbed.
• Aeroplane cruises as a result of balance between force due to gravity and upthrust.
• Walking is also an example of balanced equilibrium, if the gravity would have been lesser than we could have started floating mid air.

There are numerous examples in daily lives where we can thank equilibrium for existing. Without equilibrium we couldn’t be having such simplicity in our lives.

Abhishek

I, Abhishek Khambhata, have pursued Btech in Mechanical Engineering. Throughout four years of my engineering, I have designed and flown unmanned aerial vehicles. My forte is fluid mechanics and thermal engineering. My fourth year project was based on performance enhancement of unmanned aerial vehicles using solar technology. I would like to connect with like minded people.