Exploring Inelastic Collisions: Energy Conservation

In summary, the conversation discusses an experiment where the law of conservation of energy cannot be applied due to the loss of kinetic energy. However, this is not always the case in inelastic collisions, as demonstrated by the ball hitting the ground and producing sound energy. The book's statement that conservation of energy cannot be applied in elastic collisions is a case of careless wording and should instead specify that conservation of mechanical energy cannot be applied. The broader concept of conservation of energy, including other forms like sound, always applies.
  • #1
385
0
hi,
Look at this experiment
http://img243.imageshack.us/img243/4150/inelasticcollision2.jpg [Broken]

http://img13.imageshack.us/img13/2914/inelastic2.jpg [Broken]

in this experiment , the law of conservation of energy can't be applied because the KE is lost
but this is not true for all the cases of inelastic collision.
for example
when the ball hits the ground , we hear a sound and if the ball rebounded it doesn't reach the same height because KE is converted into sound energy but not lost so law of conservation of energy can be applied although its inelastic collision.

so why the book wrote that "in elastic collision the law of conservation of energy can't be applied"
although this doesn't work at all cases (i think so)
 
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  • #2
It's just a case of careless wording in the book.
It should say that conservation of mechanical (in this case k.e. and p.e.) energy cannot be applied. The broader application of conservation of energy, where you include other forms such as sound, always applies.
In many books, when dealing with mechanics problems like this one, "energy" is taken to mean mechanical energy.
 
  • #3
Yes , thank you
 

1. What is an inelastic collision?

An inelastic collision is a type of collision where the kinetic energy of the system is not conserved. This means that some of the initial kinetic energy is converted into other forms, such as thermal or sound energy. In this type of collision, the objects involved may stick together or deform, resulting in a loss of energy.

2. How is energy conserved in an inelastic collision?

In an inelastic collision, although the kinetic energy may not be conserved, the total energy of the system is still conserved. This means that the initial energy of the system before the collision is equal to the final energy of the system after the collision. Some of the initial kinetic energy is converted into other forms, but the total energy remains the same.

3. What is the difference between an inelastic collision and an elastic collision?

In an elastic collision, both the kinetic energy and the total energy of the system are conserved. This means that the objects involved bounce off each other without any energy being lost. In an inelastic collision, some of the initial kinetic energy is lost and converted into other forms of energy, resulting in a decrease in the total energy of the system.

4. What factors affect the amount of energy lost in an inelastic collision?

The amount of energy lost in an inelastic collision depends on several factors, such as the materials and shapes of the objects involved, the speed of the objects, and the angle at which they collide. Objects with less elastic materials or greater mass tend to lose more energy in a collision.

5. How is the coefficient of restitution used to measure the elasticity of a collision?

The coefficient of restitution is a measurement of the elasticity of a collision. It is defined as the ratio of the relative velocity of separation to the relative velocity of approach. A value of 1 indicates a perfectly elastic collision, where no energy is lost, while a value of 0 indicates a completely inelastic collision, where all of the initial kinetic energy is lost. Values in between 0 and 1 represent partially elastic collisions, where some energy is lost but not all.

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