Inelastic Collision and kinetic energy?

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Homework Help Overview

The problem involves an inelastic collision between two pieces of taffy, where one piece is initially at rest. The discussion centers on the conservation of momentum and the loss of kinetic energy, specifically how much kinetic energy is converted into heat during the collision. There is also a consideration of a scenario where the initial piece of taffy has double the mass of the stationary piece.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between kinetic energy and momentum in the context of inelastic collisions. There are questions about how to relate mass and velocity changes to kinetic energy loss and the implications of different mass scenarios on the final velocity and energy calculations.

Discussion Status

The discussion is ongoing, with participants exploring the concepts of conservation of momentum and the transformation of kinetic energy into heat. Some guidance has been offered regarding the investigation of inelastic collisions and the need to determine final velocities based on initial conditions, but no consensus has been reached on specific calculations or outcomes.

Contextual Notes

Participants are considering the implications of mass differences in the collision scenario and how that affects the kinetic energy and momentum equations. There is an acknowledgment of the need to reference external materials for further clarification on inelastic collisions.

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Homework Statement


A piece of taffy slams into and sticks to another identical piece of taffy that is at rest. The momentum of the two pieces stuck together after the collision is the same as it was before the collision, but this is not true of the kinetic energy, which is partly turned into heat. What percentage of the kinetic energy is turned into heat?

(my own addition) What if the initial piece of taffy was twice as massive as the one at rest when it collided?

Homework Equations

The Attempt at a Solution


Something with the equation for kinetic energy? Or is it conservation of momentum because of twice the mass and the same velocity? Not sure how the second relates to loss of energy for friction.
 
Last edited:
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They're asking about kinetic energy being turned into heat. If some of it is turned into heat then that portion will no longer be contributing to the (bulk) motion of the system.

You have a perfectly inelastic collision. What's conserved? What's the KE before and the KE after collision?
 
Well, the KE isn't conserved since it's lost to heat... but momentum has to be conserved, but I don't see how the equation for that would lead to KE if I just figure out the mass and velocity changes.

If they were the same, but double the mass in the second case... velocity would have to change? And with mv I could find the KE?
 
Last edited:
tvshonk said:
Well, the KE isn't conserved since it's lost to heat... but momentum has to be conserved, but I don't see how the equation for that would lead to KE if I just figure out the mass and velocity changes.
Look in your text, class notes, or on the web to investigate "inelastic collision". How do you determine the final velocity giving the initial masses and velocities of the colliding bodies?
If they were the same, but double the mass in the second case... velocity would have to change? And with mv I could find the KE?
Sure. You know the mass, so if you know mv you can find v, right? What's the expression for KE?
 

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