Impacts can be classified into various types. A central impact occurs when two objects collide head-on with opposite velocities aligned along the line of impact. Oblique impact occurs when two objects collide at an angle, causing a change in direction and velocity. The ratio of the relative velocity after and before the impact is the coefficient of restitution. It measures the elasticity of a collision and ranges from zero to one. Factors like impact velocity, size, and shape of the colliding bodies affect the coefficient of restitution. A perfectly elastic impact occurs when the coefficient of restitution is one, and there is no loss of kinetic energy. However, achieving perfect elasticity is impossible. During the collision, a part of kinetic energy is always lost in some form. When the coefficient of restitution is zero, the impact is called a plastic impact, wherein the colliding particles stick together and move with a common velocity after the collision. The coefficient of restitution determines the bounciness of an object. Higher values indicate a greater bounce-back with the original speed.