Collisions – Class 11 | Chapter – 6 | Physics Short Notes Series PDF for NEET & JEE

Collisions: In physics, a collision is an event in which two or more objects come into contact with each other, exchange energy and/or momentum, and then separate. Collisions can be classified into two categories: elastic collisions and inelastic collisions. During a collision, the objects involved can experience deformation, change in shape, and/or change in velocity. The behavior of the objects before and after the collision can be analyzed using the laws of conservation of energy and momentum, which state that the total amount of energy and momentum in a closed system is conserved, meaning that they cannot be created or destroyed, but can be transferred from one object to another.

Types of Collisions

There are two main types of collision in physics:

• Elastic Collision: In an elastic collision, the total kinetic energy of the objects before and after the collision is conserved. In other words, the objects bounce off each other and return to their original shapes and velocities after the collision. The kinetic energy is transferred from one object to the other without any loss. Elastic collisions are idealized and rarely occur in the real world, but they are a useful model for understanding the behavior of some systems.
• Inelastic Collision: In an inelastic collision, the total kinetic energy of the objects before and after the collision is not conserved. Some of the kinetic energy is lost in the collision, usually as heat, sound, or deformation of the objects. The objects involved in the collision stick together after the collision or one object may continue to move after the collision. Inelastic collisions are more common than elastic collisions in everyday life. Inelastic collision can be further divided into two types:
• Completely Inelastic Collision: In a completely inelastic collision, the objects stick together after the collision and move together as a single object. The kinetic energy is not conserved, and some of the energy is lost as heat, sound, and deformation of the objects.
• Partially Inelastic Collision: In a partially inelastic collision, the objects stick together for a short period after the collision and then separate. Some of the kinetic energy is lost in the collision, but the objects do not stick together permanently.

The behavior of objects in collisions can be described using the laws of conservation of energy and momentum. These laws state that the total amount of energy and momentum in a closed system is conserved, meaning that they cannot be created or destroyed, but can be transferred from one object to another.

Applications of Collisions

The study of collision has many practical applications in various fields, including:

• Automotive safety: The design of car safety features, such as seat belts, airbags, and crumple zones, rely on an understanding of the behavior of objects in collisions. Car manufacturers use crash testing to evaluate the safety of their vehicles.
• Sports: The rules and equipment in sports like football, hockey, and soccer are designed with an understanding of the behavior of objects in collisions. Helmets and pads are used in contact sports to reduce the risk of injury during collisions.
• Engineering: Collisions are used in engineering to test the safety and durability of products. For example, crash testing is used to evaluate the safety of aircraft, trains, and buildings during an earthquake.
• Particle physics: Collisions are used in particle accelerators to study the behavior of subatomic particles. The Large Hadron Collider (LHC) is the world’s largest and most powerful particle accelerator, and it is used to investigate the properties of matter and the nature of the universe.
• Astronomy: Collisions play a critical role in the formation of planets and stars. When two objects in space collide, they can merge to form a larger object. This process is thought to be responsible for the formation of the Moon, as well as many asteroids and comets.
• Chemistry: In chemistry, collisions between molecules are responsible for chemical reactions. The rate and outcome of a chemical reaction depend on the energy and orientation of the colliding molecules.

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