Inelastic Collision and kinetic energy?

In summary, when a piece of taffy collides with another identical piece and sticks to it, the momentum of the two combined pieces remains the same, but the kinetic energy is partially converted into heat. The percentage of kinetic energy converted into heat can be determined by using the equation for kinetic energy and knowing the masses and velocities of the colliding pieces. In the scenario where the initial piece of taffy is twice as massive as the one at rest, the velocity would change and the kinetic energy can be found using the mass and velocity. This is due to the fact that in an inelastic collision, momentum is conserved but kinetic energy is not. In order to determine the final velocity of the colliding bodies, one can use
  • #1
tvshonk
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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.
 
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  • #2
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?
 
  • #3
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?
 
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  • #4
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?
 

1. What is an inelastic collision?

An inelastic collision is a type of collision in which kinetic energy is not conserved. This means that the total energy of the system before and after the collision is not the same.

2. How is kinetic energy affected by an inelastic collision?

In an inelastic collision, kinetic energy is typically reduced. This is because some of the kinetic energy is converted into other forms of energy, such as heat or sound.

3. What is the equation for calculating kinetic energy in an inelastic collision?

The equation for calculating kinetic energy in an inelastic collision is KE = 1/2 * m * v^2, where KE is the kinetic energy, m is the mass of the object, and v is the velocity.

4. Can kinetic energy be negative in an inelastic collision?

Yes, kinetic energy can be negative in an inelastic collision. This occurs when the final velocity of the object is in the opposite direction of its initial velocity.

5. How does the coefficient of restitution relate to kinetic energy in an inelastic collision?

The coefficient of restitution, which is a measure of the elasticity of a collision, is related to kinetic energy in an inelastic collision by the equation e = √(KE after / KE before). This means that a lower coefficient of restitution corresponds to a greater loss of kinetic energy in the collision.

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