1. ## Two balls...

Two balls with masses of 2.0 kg and 6.0 kg travel toward each other at speeds of 12 m/s and 4.0 m/s, respectively. If the balls have a head-on, inelastic collision and the 2.0-kg ball recoils with a speed of 8.0 m/s, how much kinetic energy is lost in the collision?

2. Originally Posted by Candy
Two balls with masses of 2.0 kg and 6.0 kg travel toward each other at speeds of 12 m/s and 4.0 m/s, respectively. If the balls have a head-on, inelastic collision and the 2.0-kg ball recoils with a speed of 8.0 m/s, how much kinetic energy is lost in the collision?
You have initial kinetic energy $\displaystyle KE_{initial}$, and momentum $\displaystyle p_{initial}$:

$\displaystyle KE_{initial}=\frac{2.12^2+6.4^2}{2}=192\ \mathrm{J}$

$\displaystyle p_{initial}=2.12+6.(-4)=0\ \mathrm{kg.m.s^{-1}}$.

As linear momentum is conserved in the collision:

$\displaystyle p_{final}=p_{initial}=0=2.(-8)+4.v$,

where $\displaystyle v$ is the final velocity of the second particle.

Hence:

$\displaystyle v=4\ \mathrm{m/s}$,

so the final kinetic energy is:

$\displaystyle KE_{final}=\frac{2.8^2+6.4^2}{2}=112 \ \mathrm{J}$,

so $\displaystyle 80\ \mathrm{J}$ are lost

RonL

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### physics Two balls with masses of 2.0kg and 6.0kg travel toward each other at speeds of 12 m/s and 4.0 m/s respectivly. If the balls have a head on inelastic collision and the 2.0 kg ball recoils with a speed of 8.0 m/s how much kinetic energy is lost in t

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