# Difference Between Inelastic and Elastic Collisions

Edited by Diffzy | Updated on: April 30, 2023

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## Introduction

A fully elastic collision means no kinetic energy is lost during contact. In an inelastic collision, kinetic energy is not converted into another type of energy. Any macroscopic collision between objects will transform a portion of the kinetic energy into internal and other types of energy, so there are no fully elastic large-scale interactions. In inelastic collisions, momentum is preserved, but kinetic energy cannot be tracked because part of it is transformed into other types of energy. As collisions in ideal gases approach perfectly elastic collisions, scattering interactions of subatomic particles deflected by the electromagnetic field also approach perfectly elastic collisions. Large-scale interactions that work like a slingshot, like the gravity between satellites and planets, are fully elastic.

It is helpful to determine the limit case of an elastic collision, as collisions between hard spheres may be virtually elastic. The idea that momentum and kinetic energy stay the same makes it possible to figure out the final speeds of two objects that hit each other.

A collision happens when two objects or bodies come into direct contact. It is the act or occurrence of particles of different masses colliding or meeting. Both bodies exert pressure on one another during this occurrence. There are two types of collisions: elastic collisions and inelastic collisions.

## Elastic vs. Inelastic Collision

In an elastic collision, the kinetic energy remains constant during the collision, but in an inelastic collision, the kinetic energy changes throughout the impact. This collision is called an elastic collision when the kinetic energy is not transformed into other types of energy, such as heat or sound energy. Momentum and kinetic energy are maintained during elastic collisions. In addition, the forces do not transform into new forms; they remain unchanged.

A collision is inelastic when the kinetic energy transforms into any other kind of energy, transforming into several forms of energy. While momentum is preserved, kinetic energy is not. During a collision, the forces change.

There are two primary types of collisions: elastic and inelastic. An elastic collision is when the colliding items rebound without deforming or generating heat. When two things hit each other, they are deformed, and heat is made. This is called an inelastic collision.

Before and after an elastic impact, the momentum and total kinetic energy are the same. In other words, the total kinetic energy and momentum are preserved throughout the elastic contact. Therefore, there is no energy loss in an elastic collision. The action of the swinging balls exemplifies an elastic collision.

In an inelastic collision, energy is transformed into other forms of energy, such as sound or heat energy. In an inelastic collision, energy is not conserved. An automotive collision is an example of an inelastic collision.

Elastic collisions have the following characteristics: kinetic energy is conserved, linear momentum is conserved, and total energy is conserved. During an elastic collision, the forces stay the same, and the mechanical energy does not change into other types of energy, like acoustic or thermal energy.

From the point of view of the average person, the main difference between an inelastic and an elastic collision is how the kinetic energy is changed.

## What is a Collision?

In a collision, a relatively large force applies for a relatively brief period to each colliding particle. The basic idea behind a collision is that the motion of the colliding particles (or at least one) changes suddenly. This lets us clearly distinguish between "before the collision" and "after the collision."

When a bat strikes a baseball, for instance, the origin and conclusion of the impact can be precisely identified. The bat is in contact with the ball for a relatively short period compared to the time we see the ball. During impact, the bat puts a substantial force on the ball. This force fluctuates with time in a complicated manner that is difficult to quantify. Upon impact, both the ball and the bat are distorted. Impulsive forces are forces that act for a short time compared to the amount of time that can be spent observing the system.

When an alpha particle (helium nucleus) collides with another nucleus, the force between them may be the well-known electrostatic repulsion linked with the particles' charges. Even if the particles don't hit each other, we can still call it a collision because a fairly strong force acting for a concise amount of time compared to the time an alpha particle is observed a big effect on its path.

The speed and direction of a space probe can be altered in a "close encounter" with a moving planet during a collision between a space probe and a planet, referred to as the "slingshot effect." The space probe does not contact the planet, but it comes under its gravitational pull for a relatively brief period relative to the direction of its voyage. Thus, it is appropriate to refer to such occurrences as "collisions."

A system's momentum is determined by its mass and velocity. A system is a collection of entities bounded by distinct boundaries. An isolated system is a collection of interacting entities on which no external force is operating. If no net or unbalanced force applies to a system, its momentum stays unchanged. Thus, momentum is always preserved in an isolated system. This is the Momentum Conservation Law.

Consider a system consisting of two spheres with masses  m1 and m2 in isolation. They are traveling in a straight line with respective beginning velocities of u1 and u2but  u1 is more significant than u2 As they advance, the sphere of mass  m1 approaches the sphere of mass m2.

The initial momentum of mass m1 equals mass u1.

m2 initial momentum equals m2 x u2

Before the collision, the total starting momentum of the system is m1 u1 plus m2 —--(1).

Eventually, mass  m1and m2  impacts mass with some force.

Newton's third law of motion states that m2 it exerts an equal and opposite force on  m1. After contact, their velocities should become v1 v2 correspondingly. Then:

m1 =  m1v1

Final mass momentum m2 = m2v2

The total momentum of the system after the collision is equal to m1v1 plus m2v1 —------(2).

The law of conservation of momentum states that the system's total initial momentum before contact equals the total final momentum after impact.

m1 u1 + m2 =  m1 v1 + m2v2.

Following the rule of conservation of momentum, Eq—------------(3)

demonstrates that the momentum of a system before and after collisions is unchanged. The law of momentum conservation is an essential rule with several applications.

### Is momentum preserved upon inelastic impact?

A system's momentum is determined by its mass and velocity. A system is a collection of entities bounded by distinct boundaries. An isolated system is a collection of interacting entities on which no external force is operating. If no net or unbalanced force applies to a system, its momentum stays unchanged. Thus, momentum is always preserved in an isolated system. This is the Momentum Conservation Law.

Consider a balloon filled with air, as specified by the third law of motion. In this instance, the balloon and the air within it constitute a system. Before the balloon was released, the system was at rest, and its initial momentum was thus zero. As soon as the balloon is released, air is expelled with considerable velocity. The air that escapes from it processes momentum. To conserve momentum, the balloon travels in the opposite direction of air expulsion.

## What are Elastic Collisions?

A collision is elastic if the form of energy remains unchanged during the impact. An ideal collision would be an elastic collision. The impact does not affect the kinetic energy, the same before and after. This is because energy and momentum are always kept the same.

Kinetic energy does not transform into types of energy such as light, heat, or sound. In an elastic collision, there is no change in size or shape. No energy sources are squandered. This collision happens between molecules of gas or air. It can only occur with microparticles. This sort of accident is rare in our everyday lives.

Momentum and kinetic energy are kept when, for example, a ball is dropped on the floor and bounces back up.

## What are Inelastic collisions?

An inelastic collision is a process in which energy forms are different before and after contact. While momentum stays the same before and after a collision, kinetic energy changes. The kinetic energy is converted into other types of energy, such as thermal or acoustic energy. In this procedure, heat is produced.

In an inelastic collision, the body's size and shape are deformed, and energy is lost. It happens predominantly in liquids and solids and is reasonable only for macro-objects. This collision occurs in our daily lives.

For instance, when two trolleys meet and get magnetically coupled after impact, they create a single connected mass. This collision is called inelastic because the kinetic energy changes, but the momentum stays the same.

Because kinetic energy is transferred with each contact between the molecules' internal degrees of freedom and translational motion, completely elastic collisions between gas or liquid molecules seldom occur. Half of the collisions are, to variable degrees, inelastic at any given time (the pair has less kinetic energy after the collision than before). In contrast, the other half might be categorized as "super-elastic" (possessing more kinetic energy after the collision than before). Molecular collisions are elastic throughout the whole sample.

Inelastic collisions abide by momentum conservation even if they do not save kinetic energy. The conservation of kinetic energy is only observed in straightforward cases involving ballistic pendulums when the block swings at its widest angle.

## Differences Between Elastic and Inelastic Collision in Points

• Elastic collisions occur when no other kind of energy is converted from the kinetic energy of the colliding objects. When the kinetic energy of the objects does not remain constant throughout the impact, inelastic collisions occur.
• The two objects have different speeds after an elastic contact but the same speed after an inelastic impact.
• Heat is produced during an inelastic contact, not during an elastic impact.
• An inelastic collision results in no deformation. After an elastic collision, the object's size and shape remain unchanged, whereas after an inelastic impact, the body's size and shape change.
• Energy and forces are never wasted in elastic collisions, while energy is permanently lost in inelastic collisions.
• An elastic collision does not result in the forces changing into other forms of energy, whereas an inelastic collision does.
• Between molecules of gas or air, there is an elastic collision, whereas, between molecules of liquids and solids, there is an inelastic collision.
• Only microparticles can collide elastically, whereas macroparticles can collide inelastically.
• Kinetic energy and momentum remain constant before and after an elastic contact. Momentum and energy are maintained in an inelastic collision, but not momentum.
• Swinging balls colliding is an excellent example of an elastic collision, whereas cars colliding is a good example of an inelastic collision.

## Conclusion

There are two sorts of collisions: elastic and inelastic. This collision is called an elastic collision when the kinetic energy is not transformed into other types of energy, such as heat or sound energy. A collision is inelastic when there is a change in kinetic energy during impact.

## References

• https://journals.aps.org/pr/abstract/10.1103/PhysRev.131.2115
• https://aapt.scitation.org/doi/abs/10.1119/1.1285850

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"Difference Between Inelastic and Elastic Collisions." Diffzy.com, 2024. Fri. 19 Jul. 2024. <https://www.diffzy.com/article/difference-between-inelastic-and-elastic-collisions-1043>.

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