Elastic and inelastic collision formula

In summary, the conversation discusses the concept of collisions in physics and the relationships between velocities before and after collisions. It also mentions the coefficient of restitution and its values for different types of collisions. Finally, a problem involving the rebound height of a steel ball is presented, using the conservation of momentum and kinetic energy equations.
  • #1
trust_noone
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i don't know how am i supposed to answer this Physics question..all i know its about generating a formula or something like that..here's the problem:

1.a)For an elastic, two-body head-on collisions, show that the general v2 - v1 = - (v2 - v1). That is, relative speed of recession after the collision is the same as the relative speed of approach before it.

1.b)In general, a collision is completely inelastic, completely elastic, or somewhere in between the degree of elasticity is sometimes expressed as the coefficient of restitution (e), defined as the relative velocity of recession and approach:
v2 - v1 = -e (v2o - v1o)
What are the values of e for elastic collision and a perfectly inelastic collision?


last question:
2. The coefficient of restitution for steel colliding with steel is 0.95. If steel is dropped from a height ho above steel plate, to what height will the ball rebound?

note: v,h are the coefficient while the next are its subscript..
thanks in advance..
 
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  • #2
Well you know that in both cases, momentum is conserved. But only in the elastic collision is kinetic energy conserved.

(Two equations, two unknown :wink: )
 

1. What is the equation for elastic collision?

The equation for elastic collision is m1v1 + m2v2 = m1v1' + m2v2', where m1 and m2 are the masses of the colliding objects, v1 and v2 are their velocities before the collision, and v1' and v2' are their velocities after the collision.

2. How is the equation for inelastic collision different from elastic collision?

The equation for inelastic collision is m1v1 + m2v2 = (m1 + m2)v', where m1 and m2 are the masses of the colliding objects, v1 and v2 are their velocities before the collision, and v' is their common velocity after the collision. In inelastic collisions, the objects stick together after the collision and move with a common velocity, whereas in elastic collisions, the objects bounce off each other with different velocities.

3. What factors affect the outcome of a collision?

The outcome of a collision is affected by the masses and velocities of the objects involved. In elastic collisions, the outcome is also affected by the elasticity of the objects, while in inelastic collisions, it is affected by the nature of the collision (e.g. whether the objects stick together or not).

4. How do you determine the kinetic energy before and after a collision?

The kinetic energy before a collision can be calculated using the equation KE = 1/2mv^2, where m is the mass of the object and v is its velocity. The kinetic energy after a collision can be calculated using the same equation, but using the new velocities after the collision.

5. Can the equation for elastic and inelastic collisions be applied to all types of collisions?

No, the equation for elastic and inelastic collisions can only be applied to collisions between two objects moving in a straight line with no external forces acting on them. It does not apply to rotational collisions or those with external forces, such as friction.

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