What is the Coefficient of Restitution (e)?

In Physics (Class 11, Work, Energy and Power), the Coefficient of Restitution (e) is a number that indicates how much kinetic energy is retained after two objects collide. It essentially measures the 'bounciness' of a collision.

Question (Click to Flip)

What is the coefficient of restitution?

Answer

It is the ratio of the relative velocity of separation after a collision to the relative velocity of approach before the collision. It measures how elastic a collision is.

Card 1 of 2 free previews

Key Facts

Symbol: e.

Formula: Relative velocity of separation / Relative velocity of approach.

Range: 0 ≤ e ≤ 1.

e = 1: Perfectly elastic collision.

e = 0: Perfectly inelastic collision (objects stick together).

Definition and Formula

The Coefficient of Restitution (e) is defined as the ratio of the relative velocity of separation after collision to the relative velocity of approach before collision.

Formula: e = (v₂ - v₁) / (u₁ - u₂) Where:

u₁, u₂ = Initial velocities (before collision)
v₁, v₂ = Final velocities (after collision)

Values of 'e'

The value of 'e' always lies between 0 and 1.

1. Perfectly Elastic Collision (e = 1)

Kinetic energy is completely conserved. Objects bounce off each other perfectly.
(v₂ - v₁) = (u₁ - u₂).

2. Perfectly Inelastic Collision (e = 0)

Objects stick together after colliding and move with the same velocity (v₁ = v₂).
Maximum kinetic energy is lost (converted to heat/sound).

3. Partially Elastic/Inelastic Collision (0 < e < 1)

Most real-world collisions (like a bouncing basketball). Some kinetic energy is lost.

Questions and Answers

What is the coefficient of restitution?+

It is the ratio of the relative velocity of separation after a collision to the relative velocity of approach before the collision. It measures how elastic a collision is.

What is the value of 'e' for a perfectly elastic collision?+

For a perfectly elastic collision, the coefficient of restitution (e) is exactly 1.

More in Physics

⚡

What is Time Period? (Definition and Formula)

Learn the definition of Time Period in physics. Understand how it relates to frequency, its formula (T = 1/f), and examples from pendulums and waves.

⚡

Time Period of a Simple Pendulum: Formula and Derivation

Learn the formula for the time period of a simple pendulum T=2π√(L/g). Understand what factors affect and do not affect its time period.

⚡

What is the Triple Point of Water?

Learn the definition of the triple point of water. Understand the exact temperature (273.16 K) and pressure (611.657 Pa) where water exists as solid, liquid, and gas simultaneously.

⚡

Applications of Universal Law of Gravitation

Two applications: (1) explaining planetary motion and Kepler's laws; (2) calculating mass of the Sun/Earth. Also explains tides, escape velocity, and satellite orbits.

⚡

Types of Lenses in Physics

Learn about the two main types of lenses — Convex (converging) and Concave (diverging) — with their properties, uses, and key differences.

Study Smarter with Shinyu.ai

Turn this guide into revision flashcards, a practice exam, or an AI-generated podcast — free, no signup required.