Calculating Velocity After Elastic Collision: Kinetic Energy Problem

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Homework Help Overview

The discussion revolves around a problem in mechanics involving an elastic collision between two balls of differing masses. The original poster presents a scenario where a 0.8 kg ball collides with a stationary 0.4 kg ball, seeking to determine the velocities of both balls post-collision.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the conservation of kinetic energy and momentum, with some questioning the method of dividing kinetic energy equally between the two balls. Others suggest that both energy and momentum must be conserved in the analysis.

Discussion Status

The conversation is ongoing, with participants exploring the implications of conservation laws. Some guidance has been provided regarding the need to write equations for both energy and momentum conservation, but no consensus or resolution has been reached yet.

Contextual Notes

Participants are navigating the assumptions related to the conservation of kinetic energy and momentum in elastic collisions, with some uncertainty about how to apply these principles correctly.

ashvinthecha
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Homework Statement


A ball of mass 0.8kg moving initially at 8.0m/s has a head on collision with a 0.4kg ball that is at rest. If the collision is perfectly elastic, what is the velocity of each ball after the collision?


Homework Equations


Ek=(mv2)/2


The Attempt at a Solution


I found the kinetic energy of the first ball, then split the knietic energy between the two balls after the collision to individually find the velocity of each.
 
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ashvinthecha said:
I found the kinetic energy of the first ball, then split the knietic energy between the two balls after the collision to individually find the velocity of each.
What do you mean by 'split the kinetic energy'?

Hint: What else is conserved during the collision besides energy?
 
Doc Al said:
What do you mean by 'split the kinetic energy'?

Hint: What else is conserved during the collision besides energy?

I divided the total kinetic energy by two... and is momentum the answer to your question
 
ashvinthecha said:
I divided the total kinetic energy by two...
You cannot assume that the kinetic energy divides equally.
and is momentum the answer to your question
Yes. Use conservation of momentum and energy to solve for the final speeds.
 
Doc Al said:
You cannot assume that the kinetic energy divides equally.

Yes. Use conservation of momentum and energy to solve for the final speeds.

How do I do that?
 
ashvinthecha said:
How do I do that?
Write equations for energy conservation and momentum conservation, then solve them.
 

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