# Can any of you guys help to understand coefficient

1. Apr 17, 2012

### suryanarayan

of restitution????

i have no idea what it is and how it works...also please tell me about the line of impact and
the line of tangent.....
in a semielastic collision ,how can we know the velocity of after collision ...

2. Apr 17, 2012

### HallsofIvy

Staff Emeritus
Re: can any of u guys help to understand coefficient

An "elastic" collision is one in which each colliding object returns to its original shape and energy is conserved. A "completely inelastic" collision is one in which the two colliding objects stick together and so have the same speed. Energy is not conserved.
The "coefficient of restitution" measures what percentage of kinetic energy is conserved. Since kinetic energy is $(1/2)mv^2$, if the initial speed was $v_0$ and the coefficient of restitution is $\mu$ then the kinetic energy after the collision will be given by $(1/2)mv^2= (1/2)m(\mu v_0)^2$ so $v= \mu v$.

The "line of impact" is simply the line between the centers of the two objects when they collide while the "line of tangency" is the line tangent to both objects at the point of collision.

3. Apr 17, 2012

### suryanarayan

Re: can any of u guys help to understand coefficient

but if the second object is an inclined plane at an angle 60 degree with horizontal...then what will be the line of impact???and if the first particles moves with a velocity v parallel to the horizontal and after collision it rebounds in the vertical direction ....what will be the coefficient of restitution???
i tried it many times ....by splitting the initial velcity but dont know how to proceeed because i dont know the line of impact ....